Three-Dimensional (3D) Laser-Induced Graphene: Structure, Properties, and Application to Chemical Sensing

Fabrication of a 96-electrode array using carbon dioxide laser ablation

The 96 laser-induced multigraphene electrode (96L-MGE) integrated microwell plate (96 L-MGE-MP) is described. Each cell includes separate working, auxiliary, and reference electrodes, and the array sits on a poly-methyl methacrylate (PMMA) well. The 96 electrochemical cells were fabricated by laser ablation of polyimide adhesive tape, which created laser-induced graphene electrodes (L-GE). The microwell was produced using laser ablation of the PMMA sheet as well. The morphology and electrochemical characterization of L-GE were controlled by tuning the laser processing. L-GE fabricated at laser power-laser speed ratios of 0.008-0.02 W s mm-1displayed good electrochemical behaviors. Under the optimal condition of L-GE fabrication, the measured L-GE surface roughness was 475.47 nm. The 96 L-MGE can be fabricated in 24.2 min and is compatible with various analytes. 10 benchmark redox compounds were shown as electrocatalytic examples. The performance of each analyte was investigated by voltammetry. As proof of concept, 96 L-MGE-MP was connected to a 96× connector for multichannel detection. The RSD of the 96 L-MGE-MPwas below 5.3%, which demonstrated good fabrication reproducibility.

Development of a selective electrochemical microsensor based on molecularly imprinted polydopamine/ZIF-67/laser-induced graphene for point-of-care determination of 3-nitrotyrosine

3-nitrotyrosine (3-NT) is a biomarker closely associated with the early diagnosis of oxidative stress-related disorders. The development of an accurate, cost-effective, point-of-care 3-NT sensor holds significant importance for self-monitoring and clinical treatment. In this study, a selective, sensitive, and portable molecularly imprinted electrochemical sensor was developed. ZIF-67 with strong adsorption capacity was facilely modified on an electrochemically active laser-induced graphene (LIG) substrate (formed ZIF-67/LIG). Subsequently, biocompatible dopamine was chosen as the functional monomer, and interference-free ʟ-tyrosine was used as the dummy template to create molecularly imprinted polydopamine (MIPDA) on the ZIF-67/LIG, endowing the sensor with selectivity. The morphologies, electrochemical properties, and detection performance of the sensor were comprehensively investigated using scanning electron microscopy, cyclic voltammetry, electrochemical impedance spectroscopy, and differential pulse voltammetry. To achieve the best performance, several parameters were optimized, including the number of polymerization cycles (15), elution time (60 min), incubation time (7 min), and pH of the buffer solution (6). The turnaround time for this sensor is 10 min. Benefiting from the alliance of MIPDA, ZIF-67, and LIG, the sensor exhibited excellent sensitivity with a detection limit of 6.71 nM, and distinguished selectivity against 11 interfering substances. To enable convenient clinical diagnosis, a customized electrochemical microsensor with MIPDA/ZIF-67/LIG was designed, showcasing excellent reliability and convenience in detecting biological samples without pretreatment. The proposed microsensor will not only facilitate clinical diagnosis and improve patient care, but also provide inspiration for the development of other portable and accurate electrochemical biosensors.

Controlling Thermoelectric Properties of Laser-Induced Graphene on Polyimide

In the field of wearable thermoelectric generators, graphene-based materials have attracted attention as suitable candidates due to their low material costs and tunable electronic properties. However, their high thermal conductivity poses significant challenges. Low thermal conductivity due to porous structure of the laser-induced graphene, combined with its affordability and scalability, positions it as a promising candidate for thermoelectric applications. In this study, thermoelectric properties of the laser-induced graphene (LIG) on polyimide and their dependence on structural modifications of LIG were investigated. Furthermore, it was shown that increasing the laser scribing power on polyimide results in larger graphene flakes and a higher degree of graphitization. Electrical conductivity measurements indicated an increase with increasing laser power, due to a higher degree of graphitization, which enhances charge carrier mobility. Our findings reveal that LIG exhibits p-type semiconducting behavior, characterized by a positive Seebeck coefficient. It was shown that increasing laser power increased the Seebeck coefficient and electrical conductivity simultaneously, which is attributed to a charge carrier energy filtering effect arising from structures occurred on the graphene flakes. Moreover, the porous structure of LIG contributes to its relatively low thermal conductivity, ranging between 0.6 W/m·K and 0.85 W/m·K, which enhances the thermoelectric performance of LIG. It has been observed that with increasing laser power, the figure of merit for laser-induced graphene can be enhanced by nearly 10 times, which holds promising applications for laser-induced graphene due to the tunability of its thermoelectric performance by changing laser parameters.

A laser-Engraved Wearable Electrochemical Sensing Patch for Heat Stress Precise Individual Management of Horse

In point-of-care diagnostics, the continuous monitoring of sweat constituents provides a window into individual's physiological state. For species like horses, with abundant sweat glands, sweat composition can serve as an early health indicator. Considering the salience of such metrics in the domain of high-value animal breeding, a sophisticated wearable sensor patch tailored is introduced for the dynamic assessment of equine sweat, offering insights into pH, potassium ion (K+), and temperature profiles during episodes of heat stress and under normal physiological conditions. The device integrates a laser-engraved graphene (LEG) sensing electrode array, a non-invasive iontophoretic module for stimulated sweat secretion, an adaptable signal processing unit, and an embedded wireless communication framework. Profiting from an admirable Truth Table capable of logical evaluation, the integrated system enabled the early and timely assessment for heat stress, with high accuracy, stability, and reproducibility. The sensor patch has been calibrated to align with the unique dermal and physiological contours of equine anatomy, thereby augmenting its applicability in practical settings. This real-time analysis tool for equine perspiration stands to revolutionize personalized health management approaches for high-value animals, marking a significant stride in the integration of smart technologies within the agricultural sector.

Application of digital twins for simulation based tailoring of laser induced graphene

In the era of man-machine interfaces, digital twins stand as a key technology, offering virtual representations of real-world objects, processes, and systems through computational models. They enable novel ways of interacting with, comprehending, and manipulating real-world entities within a virtual realm. The real implementation of graphene-based sensors and electronic devices remains challenging due to the integration complexities of high-quality graphene materials with existing manufacturing processes. To address this, scalable techniques for the in-situ fabrication of graphene-like materials are essential. One promising method involves using a CO2 laser to convert polyimide into graphene. Optimizing this graphitization process is hindered by complex parameter interactions and nonlinear terms. This article explores how these digital replicas can enhance the fabrication of laser-induced graphene (LIG) through laser simulation and machine learning methods to enable rapid single-step LIG patterning. This approach aims to create a universal simulation for all CO2 lasers, calculating optical energy flux and utilizing machine learning to control and predict LIG conductivity (ability to conduct current), morphology, and electrical resistance. The proposed procedure, integrating digital twins in the LIG production process, will avoid or reduce the preliminary tests required to determine the proper laser parameters to reach the desired LIG characteristics. Accordingly, this approach will reduce the time and costs associated with these tests and thus increase the efficiency and optimize the procedure.

Innovative Graphene-Based Nanocomposites for Improvement of Electrochemical Sensors: Synthesis, Characterization, and Applications

Graphene, renowned for its exceptional physicochemical attributes, has emerged as a favored substrate for integrating a wide array of inorganic and organic materials in scientific endeavors and innovations. Electrochemical graphene-based nanocomposite sensors have been developed by incorporating diverse nanoparticles into graphene, effectively immobilized onto electrodes through various techniques. These graphene-based nanocomposite sensors have effectively detected and quantified various electroactive species in samples. This review delves into using graphene nanocomposites to fabricate electrochemical sensors, leveraging the exceptional electrical, mechanical, and thermal properties inherent to graphene derivatives. These nanocomposites showcase electrocatalytic activity, substantial surface area, superior electrical conductivity, adsorption capabilities, and notable porosity, which are highly advantageous for sensing applications. A myriad of characterization techniques, including Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), BET surface area analysis, and X-ray diffraction (XRD), have proven effective in exploring the properties of graphene nanocomposites and validating the adjustable formation of these nanomaterials with graphene. The applicability of these sensors across various matrices, encompassing environmental, food, and biological domains, has been evaluated through electrochemical measurements, such as cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and differential pulse voltammetry (DPV). This review provides a comprehensive overview of synthesis methods, characterization techniques, and sensor applications pertinent to graphene-based nanocomposites. Furthermore, it deliberates on the challenges and future prospects within this burgeoning field.

Graphene and metal-organic framework hybrids for high-performance sensors for lung cancer biomarker detection supported by machine learning augmentation

Conventional diagnostic methods for lung cancer, based on breath analysis using gas chromatography and mass spectrometry, have limitations for fast screening due to their limited availability, operational complexity, and high cost. As potential replacement, among several low-cost and portable methods, chemoresistive sensors for the detection of volatile organic compounds (VOCs) that represent biomarkers of lung cancer were explored as promising solutions, which unfortunately still face challenges. To address the key problems of these sensors, such as low sensitivity, high response time, and poor selectivity, this study presents the design of new chemoresistive sensors based on hybridised porous zeolitic imidazolate (ZIF-8) based metal-organic frameworks (MOFs) and laser-scribed graphene (LSG) structures, inspired by the architecture of the human lung. The sensing performance of the fabricated ZIF-8@LSG hybrid sensors was characterised using four dominant VOC biomarkers, including acetone, ethanol, methanol, and formaldehyde, which are identified as metabolomic signatures in lung cancer patients' exhaled breath. The results using simulated breath samples showed that the sensors exhibited excellent performance for a set of these biomarkers, including fast response (2-3 seconds), a wide detection range (0.8 ppm to 50 ppm), a low detection limit (0.8 ppm), and high selectivity, all obtained at room temperature. Intelligent machine learning (ML) recognition using the multilayer perceptron (MLP)-based classification algorithm was further employed to enhance the capability of these sensors, achieving an exceptional accuracy (approximately 96.5%) for the four targeted VOCs over the tested range (0.8-10 ppm). The developed hybridised nanomaterials, combined with the ML methodology, showcase robust identification of lung cancer biomarkers in simulated breath samples containing multiple biomarkers and a promising solution for their further improvements toward practical applications.

Recent advances in implantable sensors and electronics using printable materials for advanced healthcare

This review article focuses on the recent printing technological progress in healthcare, underscoring the significant potential of implantable devices across diverse applications. Printing technologies have widespread use in developing health monitoring devices, diagnostic systems, and surgical devices. Recent years have witnessed remarkable progress in fabricating low-profile implantable devices, driven by advancements in printing technologies and nanomaterials. The importance of implantable biosensors and bioelectronics is highlighted, specifically exploring printing tools using bio-printable inks for practical applications, including a detailed examination of fabrication processes and essential parameters. This review also justifies the need for mechanical and electrical compatibility between bioelectronics and biological tissues. In addition to technological aspects, this article delves into the importance of appropriate packaging methods to enhance implantable devices' performance, compatibility, and longevity, which are made possible by integrating cutting-edge printing technology. Collectively, we aim to shed light on the holistic landscape of implantable biosensors and bioelectronics, showcasing their evolving role in advancing healthcare through innovative printing technologies.

Actuation for flexible and stretchable microdevices

Flexible and stretchable microdevices incorporate highly deformable structures, facilitating precise functionality at the micro- and millimetre scale. Flexible microdevices have showcased extensive utility in the fields of biomedicine, microfluidics, and soft robotics. Actuation plays a critical role in transforming energy between different forms, ensuring the effective operation of devices. However, when it comes to actuating flexible microdevices at the small millimetre or even microscale, translating actuation mechanisms from conventional rigid large-scale devices is not straightforward. The recent development of actuation mechanisms leverages the benefits of device flexibility, particularly in transforming conventional actuation concepts into more efficient approaches for flexible devices. Despite many reviews on soft robotics, flexible electronics, and flexible microfluidics, a specific and systematic review of the actuation mechanisms for flexible and stretchable microdevices is still lacking. Therefore, the present review aims to address this gap by providing a comprehensive overview of state-of-the-art actuation mechanisms for flexible and stretchable microdevices. We elaborate on the different actuation mechanisms based on fluid pressure, electric, magnetic, mechanical, and chemical sources, thoroughly examining and comparing the structure designs, characteristics, performance, advantages, and drawbacks of these diverse actuation mechanisms. Furthermore, the review explores the pivotal role of materials and fabrication techniques in the development of flexible and stretchable microdevices. Finally, we summarise the applications of these devices in biomedicine and soft robotics and provide perspectives on current and future research.

Laser-Induced Graphene-Based Sensors in Health Monitoring: Progress, Sensing Mechanisms, and Applications

The rising global population and improved living standards have led to an alarming increase in non-communicable diseases, notably cardiovascular and chronic respiratory diseases, posing a severe threat to human health. Wearable sensing devices, utilizing micro-sensing technology for real-time monitoring, have emerged as promising tools for disease prevention. Among various sensing platforms, graphene-based sensors have shown exceptional performance in the field of micro-sensing. Laser-induced graphene (LIG) technology, a cost-effective and facile method for graphene preparation, has gained particular attention. By converting polymer films directly into patterned graphene materials at ambient temperature and pressure, LIG offers a convenient and environmentally friendly alternative to traditional methods, opening up innovative possibilities for electronic device fabrication. Integrating LIG-based sensors into health monitoring systems holds the potential to revolutionize health management. To commemorate the tenth anniversary of the discovery of LIG, this work provides a comprehensive overview of LIG's evolution and the progress of LIG-based sensors. Delving into the diverse sensing mechanisms of LIG-based sensors, recent research advances in the domain of health monitoring are explored. Furthermore, the opportunities and challenges associated with LIG-based sensors in health monitoring are briefly discussed.

Improving high throughput manufacture of laser-inscribed graphene electrodes via hierarchical clustering

Laser-inscribed graphene (LIG), initially developed for graphene supercapacitors, has found widespread use in sensor research and development, particularly as a platform for low-cost electrochemical sensing. However, batch-to-batch variation in LIG fabrication introduces uncertainty that cannot be adequately tracked during manufacturing process, limiting scalability. Therefore, there is an urgent need for robust quality control (QC) methodologies to identify and select similar and functional LIG electrodes for sensor fabrication. For the first time, we have developed a statistical workflow and an open-source hierarchical clustering tool for QC analysis in LIG electrode fabrication. The QC process was challenged with multi-operator cyclic voltammetry (CV) data for bare and metalized LIG. As a proof of concept, we employed the developed QC process for laboratory-scale manufacturing of LIG-based biosensors. The study demonstrates that our QC process can rapidly identify similar LIG electrodes from large batches (n ≥ 36) of electrodes, leading to a reduction in biosensor measurement variation by approximately 13% compared to the control group without QC. The statistical workflow and open-source code presented here provide a versatile toolkit for clustering analysis, opening a pathway toward scalable manufacturing of LIG electrodes in sensing. In addition, we establish a data repository for further study of LIG variation.

Recent Trends of Bioanalytical Sensors with Smart Health Monitoring Systems: From Materials to Applications

Smart biosensors attract significant interest due to real-time monitoring of user health status, where bioanalytical electronic devices designed to detect various activities and biomarkers in the human body have potential applications in physical sign monitoring and health care. Bioelectronics can be well integrated by output signals with wireless communication modules for transferring data to portable devices used as smart biosensors in performing real-time diagnosis and analysis. In this review, the scientific keys of biosensing devices and the current trends in the field of smart biosensors, (functional materials, technological approaches, sensing mechanisms, main roles, potential applications and challenges in health monitoring) will be summarized. Recent advances in the design and manufacturing of bioanalytical sensors with smarter capabilities and enhanced reliability indicate a forthcoming expansion of these smart devices from laboratory to clinical analysis. Therefore, a general description of functional materials and technological approaches used in bioelectronics will be presented after the sections of scientific keys to bioanalytical sensors. A careful introduction to the established systems of smart monitoring and prediction analysis using bioelectronics, regarding the integration of machine-learning-based basic algorithms, will be discussed. Afterward, applications and challenges in development using these smart bioelectronics in biological, clinical, and medical diagnostics will also be analyzed. Finally, the review will conclude with outlooks of smart biosensing devices assisted by machine learning algorithms, wireless communications, or smartphone-based systems on current trends and challenges for future works in wearable health monitoring.

Laser-induced graphene trending in biosensors: understanding electrode shelf-life of this highly porous material

Laser-induced graphene (LIG) has received much attention in recent years as a possible transducer material for electroanalytical sensors. Its simplicity of fabrication and good electrochemical performance are typically highlighted. However, we found that unmodified and untreated LIG electrodes had a limited shelf-life for certain electroanalytical applications, likely due to the adsorption of adventitious hydrocarbons from the storage environment. Electrode responses did not change immediately after exposure to ambient conditions but over longer periods of time, probably due to the immense specific surface area of the LIG material. LIG shelf-life is seldomly discussed prominently in the literature, yet overall trends for solutions to this challenge can be identified. Such findings from the literature regarding the long-term storage stability of LIG electrodes, pure and modified, are discussed here along with explanations for likely protective mechanisms. Specifically, applying a protective coating on LIG electrodes after manufacture is possibly the easiest method to preserve electrode functionality and should be identified as a trend for well-performing LIG electrodes in the future. Furthermore, suggested influences of the accompanying LIG microstructure/morphology on electrode characteristics are evaluated.

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

Direct Laser Writing (DLW) has been increasingly selected as a microfabrication route for efficient, cost-effective, high-resolution material synthesis and conversion. Concurrently, lasers participate in the patterning and assembly of functional geometries in several fields of application, of which electronics stand out. In this review, recent advances and strategies based on DLW for electronics microfabrication are surveyed and outlined, based on laser material growth strategies. First, the main DLW parameters influencing material synthesis and transformation mechanisms are summarized, aimed at selective, tailored writing of conductive and semiconducting materials. Additive and transformative DLW processing mechanisms are discussed, to open space to explore several categories of materials directly synthesized or transformed for electronics microfabrication. These include metallic conductors, metal oxides, transition metal chalcogenides and carbides, laser-induced graphene, and their mixtures. By accessing a wide range of material types, DLW-based electronic applications are explored, including processing components, energy harvesting and storage, sensing, and bioelectronics. The expanded capability of lasers to participate in multiple fabrication steps at different implementation levels, from material engineering to device processing, indicates their future applicability to next-generation electronics, where more accessible, green microfabrication approaches integrate lasers as comprehensive tools.

Automatically Aligned and Environment-Friendly Twisted Stacking Terahertz Chiral Metasurface with Giant Circular Dichroism for Rapid Biosensing

Chiral metasurfaces are capable of generating a huge superchiral field, which has great potential in optoelectronics and biosensing. However, the conventional fabrication process suffers greatly from time consumption, high cost, and difficult multilayer alignment, which hinder its commercial application. Herein, we propose a twisted stacking carbon-based terahertz (THz) chiral metasurface (TCM) based on laser-induced graphene (LIG) technology. By repeating a two-step process of sticking a polyimide film, followed by laser direct writing, the two layers of the TCM are aligned automatically in the fabrication. Laser manufacturing also brings such high processing speed that a TCM with a size of 15 × 15 mm can be prepared in 60 s. In addition, due to the greater dissipation of LIG than that of metals in the THz band, a giant circular dichroism (CD) of +99.5 to -99.6% is experimentally realized. The THz biosensing of bovine serum albumin enhanced by the proposed TCMs is then demonstrated. A wide sensing range (0.5-50 mg mL-1) and a good sensitivity [ΔCD: 2.09% (mg mL-1)-1, Δf: 0.0034 THz (mg mL-1)-1] are proved. This LIG-based TCM provides an environment-friendly platform for chiral research and has great application potential in rapid and low-cost commercial biosensing.

Nonenzymatic Potentiometric Detection of Ascorbic Acid with Porphyrin/ZnO-Functionalized Laser-Induced Graphene as an Electrode of EGFET Sensors

Laser-induced graphene (LIG) has emerged as a highly versatile material with significant potential in the development of electrochemical sensors. In this paper, we investigate the use of LIG and LIG functionalized with ZnO and porphyrins-ZnO as the gate electrodes of the extended gate field effect transistors (EGFETs). The resultant sensors exhibit remarkable sensitivity and selectivity, particularly toward ascorbic acid. The intrinsic sensitivity of LIG undergoes a notable enhancement through the incorporation of hybrid organic-inorganic materials. Among the variations tested, the LIG electrode coated with zinc tetraphenylporphyrin-capped ZnO nanoparticles demonstrates superior performance, reaching a limit of detection of approximately 3 nM. Furthermore, the signal ratio for 5 μM ascorbic acid relative to the same concentration of dopamine exceeds 250. The practical applicability of these sensors is demonstrated through the detection of ascorbic acid in real-world samples, specifically in a commercially available food supplement containing l-arginine. Notably, formulations with added vitamin C exhibit signals at least 25 times larger than those without, underscoring the sensors' capability to discern and quantify the presence of ascorbic acid in complex matrices. This research not only highlights the enhanced performance of LIG-based sensors through functionalization but also underscores their potential for practical applications in the analysis of vitamin-rich supplements.

2D nanomaterials for realization of flexible and wearable gas sensors: A review

Gas sensors are extensively employed for monitoring and detection of hazardous gases and vapors. Many of them are produced on rigid substrates, but flexible and wearable gas sensors are needed for intriguing usage including the internet of things (IoT) and medical devices. The materials with the greatest potential for the fabrication of flexible and wearable gas sensing devices are two-dimensional (2D) semiconducting nanomaterials, which consist of graphene and its substitutes, transition metal dichalcogenides, and MXenes. These types of materials have good mechanical flexibility, high charge carrier mobility, a large area of surface, an abundance of defects and dangling bonds, and, in certain instances adequate transparency and ease of synthesis. In this review, we have addressed the different 2D nonmaterial properties for gas sensing in the context of fabrication of flexible/wearable gas sensors. We have discussed the sensing performance of flexible/wearable gas sensors in various forms such as pristine, composite and noble metal decorated. We believe that content of this review paper is greatly useful for the researchers working in the research area of fabrication of flexible/wearable gas sensors.

Smart and emerging point of care electrochemical sensors based on nanomaterials for SARS-CoV-2 virus detection: Towards designing a future rapid diagnostic tool

In the recent years, researchers from all over the world have become interested in the fabrication of advanced and innovative electrochemical and/or biosensors for respiratory virus detection with the use of nanotechnology. These fabricated sensors demonstrated a number of benefits, including precision, affordability, accessibility, and miniaturization which makes them a promising test method for point-of-care (PoC) screening for SARS-CoV-2 viral infection. In order to comprehend the principles of electrochemical sensing and the role of various types of sensing interfaces, we comprehensively explored the underlying principles of electroanalytical methods and terminologies related to it in this review. In addition, it is addressed how to fabricate electrochemical sensing devices incorporating nanomaterials as graphene, metal/metal oxides, metal organic frameworks (MOFs), MXenes, quantum dots, and polymers. We took an effort to carefully compile current developments, advantages, drawbacks, possible solutions in nanomaterials based electrochemical sensors.

Laser-Assisted Structuring of Graphene Films with Biocompatible Liquid Crystal Polymer for Skin/Brain-Interfaced Electrodes

The work presented here introduces a facile strategy for the development of flexible and stretchable electrodes that harness the robust characteristics of carbon nanomaterials through laser processing techniques on a liquid crystal polymer (LCP) film. By utilizing LCP film as a biocompatible electronic substrate, control is demonstrated over the laser irradiation parameters to achieve efficient pattern generation and transfer printing processes, thereby yielding highly conductive laser-induced graphene (LIG) bioelectrodes. To enhance the resolution of the patterned LIG film, shadow masks are employed during laser scanning on the LCP film surface. This approach is compatible with surface-mounted device integration, enabling the circuit writing of LIG/LCP materials in a flexible format. Moreover, kirigami-inspired on-skin bioelectrodes are introduced that exhibit reasonable stretchability, enabling independent connections to healthcare hardware platforms for electrocardiogram (ECG) and electromyography (EMG) measurements. Additionally, a brain-interfaced LIG microelectrode array is proposed that combines mechanically compliant architectures with LCP encapsulation for stimulation and recording purposes, leveraging their advantageous structural features and superior electrochemical properties. This developed approach offers a cost-effective and scalable route for producing patterned arrays of laser-converted graphene as bioelectrodes. These bioelectrodes serve as ideal circuit-enabled flexible substrates with long-term reliability in the ionic environment of the human body.

A laser-induced graphene-based electrochemical immunosensor for nucleic acid methylation detection

The detection of methylation in DNA and RNA is essential for the diagnosis and treatment of a wide range of diseases. A one-step fabricated laser-induced graphene (LIG) electrode has received increasing attention due to its good electrical conductivity, large specific surface area, ease of miniaturization, low cost and flexibility. Herein, a potential biosensor for N6-methyladenosine (m6A-RNA) and 5-methylcystosine-single strand DNA (5mC-ssDNA) detection was designed. The aim of this paper is to address the problem of detecting the m6A-RNA and 5mC-ssDNA content in cells. By stepwise modification of gold nanoparticles (AuNPs), sulfhydryl-modified nucleic acid chains, biotin-modified antibodies, and streptavidin-modified horseradish peroxidase (SA-HRP) at the LIG electrode, the peak current responses exhibited an increase proportional to the concentration of m6A-RNA and 5mC-ssDNA in the hydrogen peroxide-hydroquinone (H2O2-HQ) system. This method demonstrated a low detection limit of 2.81 pM for m6A-RNA and 9.53 pM for 5mC-ssDNA, with a linear detection range of 0.01 nM to 10 nM for both targets. The regression equation was determined as ΔI = 4.83 log c + 12.32 (R2 = 0.9980) for m6A-RNA and ΔI = 9.82 log c + 22.09 (R2 = 0.9903) for 5mC-ssDNA. Our method has good selectivity toward different detection targets of nucleic acid chains, stability for long-term storage and consecutive scanning (RSD of 9.42% and 2.08%, respectively) and reproducibility of 5 electrodes (RSD of 6.85%). This method utilizes gold-sulfur bonding to immobilize the detection target, which improves the conductivity of the LIG electrode and introduces an amplified portion of the signal by taking advantage of antigen-antibody specific binding. Thus, dual detection of m6A-RNA and 5mC-ssDNA was realized. Importantly, this approach is successfully applied for the detection of targets in spiked samples extracted from HeLa cells, suggesting its potential for clinical applications and providing a new perspective for the development of point-of care testing (POCT) techniques.

Access and Management of Sweat for Non-Invasive Biomarker Monitoring: A Comprehensive Review

Sweat is an important biofluid presents in the body since it regulates the internal body temperature, and it is relatively easy to access on the skin unlike other biofluids and contains several biomarkers that are also present in the blood. Although sweat sensing devices have recently displayed tremendous progress, most of the emerging devices primarily focus on the sensor development, integration with electronics, wearability, and data from in vitro studies and short-term on-body trials during exercise. To further the advances in sweat sensing technology, this review aims to present a comprehensive report on the approaches to access and manage sweat from the skin toward improved sweat collection and sensing. It is begun by delineating the sweat secretion mechanism through the skin, and the historical perspective of sweat, followed by a detailed discussion on the mechanisms governing sweat generation and management on the skin. It is concluded by presenting the advanced applications of sweat sensing, supported by a discussion of robust, extended-operation epidermal wearable devices aiming to strengthen personalized healthcare monitoring systems.

Practical Considerations for Laser-Induced Graphene Pressure Sensors Used in Marine Applications

Small, low-power, and inexpensive marine depth sensors are of interest for a myriad of applications from maritime security to environmental monitoring. Recently, laser-induced graphene (LIG) piezoresistive pressure sensors have been proposed given their rapid fabrication and large dynamic range. In this work, the practicality of LIG integration into fieldable deep ocean (1 km) depth sensors in bulk is explored. Initially, a design of experiments (DOEs) approach evaluated laser engraver fabrication parameters such as line length, line width, laser speed, and laser power on resultant resistances of LIG traces. Next, uniaxial compression and thermal testing at relevant ocean pressures up to 10.3 MPa and temperatures between 0 and 25 °C evaluated the piezoresistive response of replicate sensors and determined the individual characterization of each, which is necessary. Additionally, bare LIG sensors showed larger resistance changes with temperature (ΔR ≈ 30 kΩ) than pressure (ΔR ≈ 1-15 kΩ), indicating that conformal coatings are required to both thermally insulate and electrically isolate traces from surrounding seawater. Sensors encapsulated with two dip-coated layers of 5 wt% polydimethylsiloxane (PDMS) silicone and submerged in water baths from 0 to 25 °C showed significant thermal dampening (ΔR ≈ 0.3 kΩ), indicating a path forward for the continued development of LIG/PDMS composite structures. This work presents both the promises and limitations of LIG piezoresistive depth sensors and recommends further research to validate this platform for global deployment.

Laser-Induced Graphitization of Polydopamine on Titania Nanotubes

Since the discovery of laser-induced graphite/graphene, there has been a notable surge of scientific interest in advancing diverse methodologies for their synthesis and applications. This study focuses on the utilization of a pulsed Nd:YAG laser to achieve graphitization of polydopamine (PDA) deposited on the surface of titania nanotubes. The partial graphitization is corroborated through Raman and XPS spectroscopies and supported by water contact angle, nanomechanical, and electrochemical measurements. Reactive molecular dynamics simulations confirm the possibility of graphitization in the nanosecond time scale with the evolution of NH3, H2O, and CO2 gases. A thorough exploration of the lasing parameter space (wavelength, pulse energy, and number of pulses) was conducted with the aim of improving either electrochemical activity or photocurrent generation. Whereas the 532 nm laser pulses interacted mostly with the PDA coating, the 365 nm pulses were absorbed by both PDA and the substrate nanotubes, leading to a higher graphitization degree. The majority of the photocurrent and quantum efficiency enhancement is observed in the visible light between 400 and 550 nm. The proposed composite is applied as a photoelectrochemical (PEC) sensor of serotonin in nanomolar concentrations. Because of the suppressed recombination and facilitated charge transfer caused by the laser graphitization, the proposed composite exhibits significantly enhanced PEC performance. In the sensing application, it showed superior sensitivity and a limit of detection competitive with nonprecious metal materials.

Design of a versatile and selective electrochemical sensor based on dummy molecularly imprinted PEDOT/laser-induced graphene for nitroaromatic explosives detection

Considering the formidable explosive power and human carcinogenicity of nitroaromatic explosives, the implementation of an accurate and sensitive detection technology is imperative for ensuring public safety and monitoring post-blast environmental contamination. In the present work, a versatile and selective electrochemical sensor based on dummy molecularly imprinted poly (3,4-ethylenedioxythiophene)/laser-induced graphene (MIPEDOT/LIG) was successfully developed and the specific detection of multiple nitroaromatic explosives was realized in the single sensor. The accessible and nontoxic trimesic acid (TMA) and superior 3, 4-ethylenedioxythiophene (EDOT) were selected as the dummy-template and the functional monomer, respectively. The interaction between the functional monomer and the template, and the morphology, electrochemical properties and detection performance of the sensor were comprehensively investigated by ultraviolet-visible spectroscopy, Fourier-transform infrared spectroscopy, scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry. Benefiting from the alliance of TMA and EDOT, the MIPEDOT/LIG sensor manifested outstanding selectivity and sensitivity for 2,4,6-trinitrotolueen (TNT), 2,4,6-trinitrophenol (TNP), 2,4-dinitrotoluene (DNT), 1,3,5-trinitrobenzene (TNB), 2,4-dinitrophenol (DNP), and 1,3-dinitrobenzene (DNB) (representative nitroaromatic explosives) with limits of determination of 1.95 ppb, 3.06 ppb, 2.49 ppb, 1.67 ppb, 1.94 ppb, and 4.56 ppb, respectively. The sensor also exhibited extraordinary reliability and convenience for environmental sample detection. Therefore, a perfect combination of versatility and selectivity in the MIPEDOT/LIG sensor was achieved. The findings of this work provide a new direction for the development of multi-target electrochemical sensors using a versatile dummy template for explosives detection.

Fabrication of Laser-Induced Graphene Based Flexible Sensors Using 355 nm Ultraviolet Laser and Their Application in Human-Computer Interaction System

In recent years, flexible sensors based on laser-induced graphene (LIG) have played an important role in areas such as smart healthcare, smart skin, and wearable devices. This paper presents the fabrication of flexible sensors based on LIG technology and their applications in human-computer interaction (HCI) systems. Firstly, LIG with a sheet resistance as low as 4.5 Ω per square was generated through direct laser interaction with commercial polyimide (PI) film. The flexible sensors were then fabricated through a one-step method using the as-prepared LIG. The applications of the flexible sensors were demonstrated by an HCI system, which was fabricated through the integration of the flexible sensors and a flexible glove. The as-prepared HCI system could detect the bending motions of different fingers and translate them into the movements of the mouse on the computer screen. At the end of the paper, a demonstration of the HCI system is presented in which words were typed on a computer screen through the bending motion of the fingers. The newly designed LIG-based flexible HCI system can be used by persons with limited mobility to control a virtual keyboard or mouse pointer, thus enhancing their accessibility and independence in the digital realm.

Robust, self-adhesive and anti-bacterial silk-based LIG electrodes for electrophysiological monitoring

Flexible wearable electrodes have been extensively used for obtaining electrophysiological signals towards smart health monitoring and disease diagnosis. Here, low-cost, and non-conductive silk fabric (SF) have been processed into highly conductive laser induced graphene (LIG) electrodes while maintaining the original structure of SF. A CO2-pulsed laser was utilized to produce LIG-SF with controlled sheet resistance and mechanical properties. Laser processing of SFs under optimized conditions yielded LIG-SF electrodes with a high degree of homogeneity on both, top and bottom layers. Silk fibroin/Ca2+ adhesive layers effectively promoted the adhesive, anti-bacterial properties and provided a conformal contact of LIG-SF electrodes with human skin. Compared with conventional Ag/AgCl electrodes, LIG-SF electrodes possesses a much lower contact impedance in contact with human skin enabling highly stable electrophysiological signals recording. The applicability of adhesive LIG-SF electrodes to acquire electrocardiogram (ECG) signals was investigated. ECG signals recordings of adhesive LIG-SF electrodes showed excellent performance compared to conventional Ag/AgCl electrodes at intense body movements while running at different speeds for up to 9 km over a duration of 24 h. Therefore, our proposed adhesive LIG-SF electrodes can be applied for long-term personalized healthcare monitoring and sports management applications.

Laser-Based Selective Material Processing for Next-Generation Additive Manufacturing

The connection between laser-based material processing and additive manufacturing is quite deeply rooted. In fact, the spark that started the field of additive manufacturing is the idea that two intersecting laser beams can selectively solidify a vat of resin. Ever since, laser has been accompanying the field of additive manufacturing, with its repertoire expanded from processing only photopolymer resin to virtually any material, allowing liberating customizability. As a result, additive manufacturing is expected to take an even more prominent role in the global supply chain in years to come. Herein, an overview of laser-based selective material processing is presented from various aspects: the physics of laser-material interactions, the materials currently used in additive manufacturing processes, the system configurations that enable laser-based additive manufacturing, and various functional applications of next-generation additive manufacturing. Additionally, current challenges and prospects of laser-based additive manufacturing are discussed.

Different Roles of Surface Chemistry and Roughness of Laser-Induced Graphene: Implications for Tunable Wettability

The control of surface wettability is a technological key aspect and usually poses considerable challenges connected to high cost, nanostructure, and durability, especially when aiming at surface patterning with high and extreme wettability contrast. This work shows a simple and scalable approach by using laser-induced graphene (LIG) and a locally inert atmosphere to continuously tune the wettability of a polyimide/LIG surface from hydrophilic to superhydrophobic (Φ ∼ 160°). This is related to the reduced amount of oxygen on the LIG surface, influenced by the local atmosphere. Furthermore, the influence of the roughness pattern of LIG on the wettability is investigated. Both approaches are combined, and the influence of surface chemistry and roughness is discussed. Measurements of the roll-off angle show that LIG scribed in an inert atmosphere with a low roughness has the highest droplet mobility with a roll-off angle of ΦRO = (1.7 ± 0.3)°. The superhydrophobic properties of the samples were maintained for over a year and showed no degradation after multiple uses. Applications of surfaces with extreme wettability contrast in millifluidics and fog basking are demonstrated. Overall, the proposed processing allows for the continuous tuning and patterning of the surface properties of LIG in a very accessible fashion useful for "lab-on-chip" applications.

Low-temperature green synthesis of few-layered graphene sheets from pomegranate peels for supercapacitor applications

Graphene presents practical applications in energy storage devices, especially supercapacitors. However, mainstream synthesis of graphene includes toxic chemical usage, which threatens the environment. With the recent attention shift to synthesizing nanomaterials from agro-waste due to their easy availability, cost-effectiveness, and, most importantly, their environmental friendliness, we present, in this work for the first time, a novel and green synthesis of few-layered graphene sheets using pomegranate peels as a precursor at a low temperature of 80 °C. The surface morphology and microstructural properties are determined by Transmission Electron Microscopy (TEM), Energy Dispersive X-Ray spectroscopy (EDX), X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), UV-visible spectroscopy (UV-vis), and the electrical properties determined by Hall Effect Measurement. The application as a supercapacitor is also examined using Cyclic Voltammetry (CV), Charge-Discharge Cycling (GCD), and Electrochemical Impedance Spectroscopy (EIS). The resulting supercapacitor delivers an areal capacitance of [Formula: see text] at a current density of 15.6 μA [Formula: see text], making our synthesized graphene a good choice for electrochemical storage devices.

Dual Colorimetric/Electrochemical Detection of Salmonella typhimurium Using a Laser-Induced Graphene Integrated Lateral Flow Immunoassay Strip

Foodborne illnesses caused by the ingestion of contaminated foods or beverages are a serious concern due to the millions of reported cases per year. It is essential to develop sensitive and rapid detection methods of foodborne pathogens to ensure food safety for producers and consumers. Unfortunately, current detection techniques still suffer from time-consuming operations and the need for highly skilled personnel. Here, we introduce a highly sensitive dual colorimetric/electrochemical detection approach for Salmonella enterica serovar typhimurium (S. typhimurium) based on a laser-induced graphene-integrated lateral flow immunoassay (LIG-LFIA) strip. The LIG electrode was fabricated by laser engraving on a polyimide tape containing a pseudo silver/silver chloride reference electrode from silver sintering and chlorination. Using double-sided tape inserted into the strip, automatic sequential reagent delivery was enabled for the dual-mode signal readout by single-sample loading. A gold-deposited gold nanoparticle strategy was first employed to simultaneously obtain a colorimetric signal for early screening and a signal turn-on electrochemical response for high-sensitivity and -quantitative analysis. A superior performance of the strip was established, characterized by a short analysis time (12 min assay +15 min sample preparation), a broad working concentration range (1 cfu/10 mL to 108 cfu/mL), and the lowest limit of detection (1 ± 0.5 cfu/10 mL; mean ± standard deviation, n = 3) among reported multimode S. typhimurium detection schemes. The strip was successfully applied in the analysis of various food products without any bacterial enrichment or amplification required, and the results were comparable to those of the standard culture method.

Direct Laser Writing of Chitosan-Borax Composites: Toward Sustainable Electrochemical Sensors

In this study, the laser-induced graphitization process of sustainable chitosan-based formulations was investigated. In particular, optimal lasing conditions were investigated alongside the effect of borax concentration in the chitosan matrix. In all cases, it was found that the obtained formulations were graphitizable with a CO2 laser. This process gave rise to the formation of high surface area, porous, and electrically conductive laser-induced graphene (LIG) structures. It was found that borax, as a cross-linker of chitosan, enabled the graphitization process when its content was ≥30 wt % in the chitosan matrix, allowing the formation of an LIG phase with a significant content of graphite-like structures. The graphitization process was investigated by thermogravimetric analysis (TGA), Raman, X-ray photoemission (XPS), and Fourier transform infrared (FTIR) spectroscopies. LIG electrodes obtained from CS/40B formulations displayed a sheet resistance as low as 110 Ω/sq. Electrochemical characterization was performed after a 10 min electrode activation by cycling in 1 M KCl. A heterogeneous electron transfer rate, k0, of 4 × 10-3 cm s-1 was determined, indicating rapid electron transfer rates at the electrode surface. These results show promise for the introduction of a new class of sustainable composites for LIG electrochemical sensing platforms.

Flexible Wearable Strain Sensors Based on Laser-Induced Graphene for Monitoring Human Physiological Signals

Flexible wearable strain sensors based on laser-induced graphene (LIG) have attracted significant interest due to their simple preparation process, three-dimensional porous structure, excellent electromechanical characteristics, and remarkable mechanical robustness. In this study, we demonstrated that LIG with various defects could be prepared on the surface of polyimide (PI) film, patterned in a single step by adjusting the scanning speed while maintaining a constant laser power of 12.4 W, and subjected to two repeated scans under ambient air conditions. The results indicated that LIG produced at a scanning speed of 70 mm/s exhibited an obvious stacked honeycomb micropore structure, and the flexible strain sensor fabricated with this material demonstrated stable resistance. The sensor exhibited high sensitivity within a low strain range of 0.4-8.0%, with the gauge factor (GF) reaching 107.8. The sensor demonstrated excellent stability and repeatable response at a strain of 2% after approximately 1000 repetitions. The flexible wearable LIG-based sensor with a serpentine bending structure could be used to detect various physiological signals, including pulse, finger bending, back of the hand relaxation and gripping, blinking eyes, smiling, drinking water, and speaking. The results of this study may serve as a reference for future applications in health monitoring, medical rehabilitation, and human-computer interactions.

Smart Multiplex Point-of-Care Platform for Simultaneous Drug Monitoring

Recently, illicit drug use has become more widespread and is linked to problems with crime and public health. These drugs disrupt consciousness, affecting perceptions and feelings. Combining stimulants and depressants to suppress the effect of drugs has become the most common reason for drug overdose deaths. On-site platforms for illicit-drug detection have gained an important role in dealing, without any excess equipment, long process, and training, with drug abuse and drug trafficking. Consequently, the development of rapid, sensitive, noninvasive, and reliable multiplex drug-detecting platforms has become a major necessity. In this study, a multiplex laser-scribed graphene (LSG) sensing platform with one counter, one reference, and three working electrodes was developed for rapid and sensitive electrochemical detection of amphetamine (AMP), cocaine (COC), and benzodiazepine (BZD) simultaneously in saliva samples. The multidetection sensing system was combined with a custom-made potentiostat to achieve a complete point-of-care (POC) platform. Smartphone integration was achieved by a customized application to operate, display, and send data. To the best of our knowledge, this is the first multiplex LSG-based electrochemical platform designed for illicit-drug detection with a custom-made potentiostat device to build a complete POC platform. Each working electrode was optimized with standard solutions of AMP, COC, and BZD in the concentration range of 1.0 pg/mL-500 ng/mL. The detection limit of each illicit drug was calculated as 4.3 ng/mL for AMP, 9.7 ng/mL for BZD, and 9.0 ng/mL for COC. Healthy and MET (methamphetamine) patient saliva samples were used for the clinical study. The multiplex LSG sensor was able to detect target analytes in real saliva samples successfully. This multiplex detection device serves the role of a practical and affordable alternative to conventional drug-detection methods by combining multiple drug detections in one portable platform.

Flash-Induced High-Throughput Porous Graphene via Synergistic Photo-Effects for Electromagnetic Interference Shielding

Porous 2D materials with high conductivity and large surface area have been proposed for potential electromagnetic interference (EMI) shielding materials in future mobility and wearable applications to prevent signal noise, transmission inaccuracy, system malfunction, and health hazards. Here, we report on the synthesis of lightweight and flexible flash-induced porous graphene (FPG) with excellent EMI shielding performance. The broad spectrum of pulsed flashlight induces photo-chemical and photo-thermal reactions in polyimide films, forming 5 × 10 cm2-size porous graphene with a hollow pillar structure in a few milliseconds. The resulting material demonstrated low density (0.0354 g cm-3) and outstanding absolute EMI shielding effectiveness of 1.12 × 105 dB cm2 g-1. The FPG was characterized via thorough material analyses, and its mechanical durability and flexibility were confirmed by a bending cycle test. Finally, the FPG was utilized in drone and wearable applications, showing effective EMI shielding performance for internal/external EMI in a drone radar system and reducing the specific absorption rate in the human body.

Bioderived Laser-Induced Graphene for Sensors and Supercapacitors

The maskless and chemical-free conversion and patterning of synthetic polymer precursors into laser-induced graphene (LIG) via laser-induced pyrolysis is a relatively new but growing field. Bioderived precursors from lignocellulosic materials can also be converted to LIG, opening a path to sustainable and environmentally friendly applications. This review is designed as a starting point for researchers who are not familiar with LIG and/or who wish to switch to sustainable bioderived precursors for their applications. Bioderived precursors are described, and their performances (mainly crystallinity and sheet resistance of the obtained LIG) are compared. The three main fields of application are reviewed: supercapacitors and electrochemical and physical sensors. The key advantages and disadvantages of each precursor for each application are discussed and compared to those of a benchmark of polymer-derived LIG. LIG from bioderived precursors can match, or even outperform, its synthetic analogue and represents a viable and sometimes better alternative, also considering its low cost and biodegradability.

Direct Laser Writing of the Porous Graphene Foam for Multiplexed Electrochemical Sweat Sensors

Wearable electrochemical sensors provide means to detect molecular-level information from the biochemical markers in biofluids for physiological health evaluation. However, a high-density array is often required for multiplexed detection of multiple markers in complex biofluids, which is challenging with low-cost fabrication methods. This work reports the low-cost direct laser writing of porous graphene foam as a flexible electrochemical sensor to detect biomarkers and electrolytes in sweat. The resulting electrochemical sensor exhibits high sensitivity and low limit of detection for various biomarkers (e.g., the sensitivity of 6.49/6.87/0.94/0.16 μA μM^-1 cm^-2 and detection limit of 0.28/0.26/1.43/11.3 μM to uric acid/dopamine/tyrosine/ascorbic acid) in sweat. The results from this work open up opportunities for noninvasive continuous monitoring of gout, hydration status, and drug intake/overdose.

Recent Advances in Flexible Piezoresistive Arrays: Materials, Design, and Applications

Spatial distribution perception has become an important trend for flexible pressure sensors, which endows wearable health devices, bionic robots, and human-machine interactive interfaces (HMI) with more precise tactile perception capabilities. Flexible pressure sensor arrays can monitor and extract abundant health information to assist in medical detection and diagnosis. Bionic robots and HMI with higher tactile perception abilities will maximize the freedom of human hands. Flexible arrays based on piezoresistive mechanisms have been extensively researched due to the high performance of pressure-sensing properties and simple readout principles. This review summarizes multiple considerations in the design of flexible piezoresistive arrays and recent advances in their development. First, frequently used piezoresistive materials and microstructures are introduced in which various strategies to improve sensor performance are presented. Second, pressure sensor arrays with spatial distribution perception capability are discussed emphatically. Crosstalk is a particular concern for sensor arrays, where mechanical and electrical sources of crosstalk issues and the corresponding solutions are highlighted. Third, several processing methods are also introduced, classified as printing, field-assisted and laser-assisted fabrication. Next, the representative application works of flexible piezoresistive arrays are provided, including human-interactive systems, healthcare devices, and some other scenarios. Finally, outlooks on the development of piezoresistive arrays are given.

Emerging technologies in wearable sensors

This Editorial highlights some current challenges and emerging solutions in wearable sensors, a maturing field where interdisciplinary crosstalk is of paramount importance. Currently, investigation efforts are aimed at expanding the application scenarios and at translating early developments from basic research to widespread adoption in personal health monitoring for diagnostic and therapeutic purposes. This translation requires addressing several old and new challenges that are summarized in this editorial. The special issue "Emerging technologies in wearable sensors" includes four selected contributions from leading researchers, exploring the topic from different perspectives. The aim is to provide the APL Bioengineering readers with a solid and timely overall vision of the field and with some recent examples of wearable sensors, exploring new research avenues.

Semiconducting MOFs on ultraviolet laser-induced graphene with a hierarchical pore architecture for NO2 monitoring

Due to rapid urbanization worldwide, monitoring the concentration of nitrogen dioxide (NO₂), which causes cardiovascular and respiratory diseases, has attracted considerable attention. Developing real-time sensors to detect parts-per-billion (ppb)-level NO₂ remains challenging due to limited sensitivity, response, and recovery characteristics. Herein, we report a hybrid structure of Cu₃HHTP₂, 2D semiconducting metal-organic frameworks (MOFs), and laser-induced graphene (LIG) for high-performance NO₂ sensing. The unique hierarchical pore architecture of LIG@Cu₃HHTP₂ promotes mass transport of gas molecules and takes full advantage of the large surface area and porosity of MOFs, enabling highly rapid and sensitive responses to NO₂. Consequently, LIG@Cu₃HHTP₂ shows one of the fastest responses and lowest limit of detection at room temperature compared with state-of-the-art NO₂ sensors. Additionally, by employing LIG as a growth platform, flexibility and patterning strategies are achieved, which are the main challenges for MOF-based electronic devices. These results provide key insight into applying MOFtronics as high-performance healthcare devices.

Laser-Induced Graphene Microsupercapacitors: Structure, Quality, and Performance

Laser-induced graphene (LIG) is a graphenic material synthesized from a polymeric substrate through point-by-point laser pyrolysis. It is a fast and cost-effective technique, and it is ideal for flexible electronics and energy storage devices, such as supercapacitors. However, the miniaturization of the thicknesses of the devices, which is important for these applications, has still not been fully explored. Therefore, this work presents an optimized set of laser conditions to fabricate high-quality LIG microsupercapacitors (MSC) from 60 µm thick polyimide substrates. This is achieved by correlating their structural morphology, material quality, and electrochemical performance. The fabricated devices show a high capacitance of 22.2 mF/cm² at 0.05 mA/cm², as well as energy and power densities comparable to those of similar devices that are hybridized with pseudocapacitive elements. The performed structural characterization confirms that the LIG material is composed of high-quality multilayer graphene nanoflakes with good structural continuity and an optimal porosity.

Salivary Glucose Detection with Laser Induced Graphene/AgNPs Non-Enzymatic Sensor

The tailoring of novel nanomaterials for sensitive glucose detection through a non-enzymatic mechanism is currently under intensive research. Here, we present a laser-induced graphene (LIG) electrode decorated with silver nanoparticles (AgNPs) as a catalytic element for the direct electrooxidation of glucose. The AgNPs were synthesized through cyclic voltammetry using LIG as a template, resulting in a porous tridimensional assembly with anchored nanostructures. The characterization corroborated the formation of LIG/AgNPs composite with distinctive peaks attributed to Ag₂O and AgO interaction with glucose. The proposed non-enzymatic sensors were successfully applied for non-enzymatic amperometric detection, exhibiting a linear range from 1 to 10 mM in the first peak (+0.7 V) and a narrow range from 1 to 2 mM with higher sensitivity of 52.2 mA/mM and improved LOD of 45 μM in the second peak (+0.55 V). The applicability of the LIG/AgNPs sensor was evaluated with spiked artificial saliva in a PoC format using a smartphone potentiostat, showing an average recovery rate of 91%. The analysis was performed in a portable, mobile, and low-cost fashion using a simulated non-invasive sample, with promising results in clinical ranges.

Wearable and Flexible Multifunctional Sensor Based on Laser-Induced Graphene for the Sports Monitoring System

The conversion of diverse polymeric substrates into laser-induced graphene (LIG) has recently emerged as a single-step method for the fabrication of patterned graphene-based wearable electronics with a wide range of applications in sensing, actuation, and energy storage. Laser-induced pyrolysis technology has many advantages over traditional graphene design: eco-friendly, designable patterning, roll-to-roll production, and controllable morphology. In this work, we designed wearable and flexible graphene-based strain and pressure sensors by laminating LIG from a commercial polyimide (PI) film. The as-prepared LIG was transferred onto a thin polydimethylsiloxane (PDMS) sheet, interwoven inside an elastic cotton sports fabric with the fabric glue as a wearable sensor. The single LIG/PDMS layer acts as a strain sensor, and a two-layer perpendicular stacking of LIG/PDMS (x and y laser-directed films) is designed for pressure sensing. This newly designed graphene textile (IGT) sensor performs four functions in volleyball sportswear, including volleyball reception detection, finger touch foul detection during blocking the ball from an opponent player, spike force measurements, and player position monitoring. An inexpensive sensor assists athletes in training and helps the coach formulate competition strategies.

Flexible Graphene-Copper Nanocomposite for Potential Wearable Electronics Applications

The demand for flexible and wearable electrochemical sensors has surged due to their low cost and portability. This study produces and characterizes low-cost and environmentally friendly flexible laser engraved graphene/Cu nanoparticles composite materials as a potential electrode for electronic applications. The electrode is fabricated by directly engraving Polyimide substrate using a CO2 laser machine to produce Laser Engraved Graphene (LEG). The electrode is then modified with copper nanoparticles via a one-step pulse electrodeposition technique to be characterized structurally, mechanically, and electrochemically using SEM, XRD, bending test, electrochemical impedance spectroscopy, and cyclic voltammetry to assess their stability and electrocatalytic activity. The laser irradiation of PI results in 3D porous graphene structure formation that increases electron transfer rate and the electrochemically active surface area. Copper deposition improves the sensitivity of LEG by its high conductivity.

Self-Assembly of a Graphene Oxide Liquid Crystal for Water Treatment

Adsorbents, especially those with high removal efficiency, long life, and multi-purpose capabilities, are the most crucial components in an adsorption system. By taking advantage of the liquid-like mobility and crystal-like ordering of liquid crystal materials, a liquid crystal induction method is developed and applied to construct three-dimensional graphene-based adsorbents featuring excellent shape adaptability, a distinctive pore structure, and abundant surface functional groups. When the monoliths are used for water restoration, the large amount of residual oxygen-containing groups is more susceptible to electrophilic attack, thus contributing to cation adsorption (up to 705.4 mg g^-1 for methylene blue), while the connected microvoids between the aligned graphene oxide sheets facilitate mass transfer, e.g., the high adsorption capacity for organic pollutants (196.2 g g^-1 for ethylene glycol) and the high evaporation rate for water (4.01 kg m^-2 h^-1). This work gives a practical method for producing high-performance graphene-based functional materials for those applications that are sensitive to surface and mass transfer properties.

Emerging Biosensing Technologies towards Early Sepsis Diagnosis and Management

Sepsis is defined as a systemic inflammatory dysfunction strictly associated with infectious diseases, which represents an important health issue whose incidence is continuously increasing worldwide. Nowadays, sepsis is considered as one of the main causes of death that mainly affects critically ill patients in clinical settings, with a higher prevalence in low-income countries. Currently, sepsis management still represents an important challenge, since the use of traditional techniques for the diagnosis does not provide a rapid response, which is crucial for an effective infection management. Biosensing systems represent a valid alternative due to their characteristics such as low cost, portability, low response time, ease of use and suitability for point of care/need applications. This review provides an overview of the infectious agents associated with the development of sepsis and the host biomarkers suitable for diagnosis and prognosis. Special focus is given to the new emerging biosensing technologies using electrochemical and optical transduction techniques for sepsis diagnosis and management.

A Self-Powered Wearable Sensor for Continuous Wireless Sweat Monitoring

Wireless wearable sweat analysis devices can monitor biomarkers at the molecular level continuously and in situ, which is highly desired for personalized health care. The miniaturization, integration, and wireless operation of sweat sensors improve the comfort and convenience while also bringing forward new challenges for power supply technology. Herein, a wireless self-powered wearable sweat analysis system (SWSAS) is designed that effectively converts the mechanical energy of human motion into electricity through hybrid nanogenerator modules (HNGMs). The HNGM shows stable output characteristics at low frequency with a current of 15 mA and a voltage of 60 V. Through real-time on-body sweat analysis powered by HNGM, the SWSAS is demonstrated to selectively monitor biomarkers (Na⁺ and K⁺ ) in sweat and wirelessly transmit the sensing data to the user interface via Bluetooth.

Stretchable Sensors and Electro-Thermal Actuators with Self-Sensing Capability Using the Laser-Induced Graphene Technology

Laser-induced graphene (LIG) represents a fast-speed and low-cost method to prepare the customizable graphene-based patterns in complex configurations with exceptional electrical performance. This paper presents the applications of LIG formed on the commercial polyimide (PI) film as the stretchable strain sensor and electrical-actuated actuators. First, the conductive performances of the LIG were systematically revealed under different fabrication conditions via investigating the effects of processing parameters, and the fluence of the laser was experimentally demonstrated as the only crucial parameter to evaluate the LIG formation, facilitating the selection of optimized manufacturing parameters to prepare the LIG with desired electrical performances. Then, the LIG-based strain sensor which can undergo over 50% tensile strain was fabricated by transfer of the LIG from the PI film to polydimethylsiloxane. The variety of LIG-based electro-thermal actuators to achieve pre-designed 3D architectures was presented, along with their parameter analysis. After incorporating the multimeter system, the actuator can even feedback its transformation from 2D precursor to 3D architecture by monitoring the resistance variation of LIG, revealing the integrated capability of our design in serving as sensors and actuators. Finally, the wearable glove with the LIG sensors was presented to demonstrate its ability to remotely control the soft robotic hand.