Tunable Pressure Sensor of f-Carbon Dot-Based Conductive Hydrogel with Electrical, Mechanical, and Shape Recovery for Monitoring Human Motion

Hydrogel-Based Continuum Soft Robots

This paper comprehensively reviews the latest advances in hydrogel-based continuum soft robots. Hydrogels exhibit exceptional flexibility and adaptability compared to traditional robots reliant on rigid structures, making them ideal as biomimetic robotic skins and platforms for constructing highly accurate, real-time responsive sensory interfaces. The article systematically summarizes recent research developments across several key dimensions, including application domains, fabrication methods, actuator technologies, and sensing mechanisms. From an application perspective, developments span healthcare, manufacturing, and agriculture. Regarding fabrication techniques, the paper extensively explores crosslinking methods, additive manufacturing, microfluidics, and other related processes. Additionally, the article categorizes and thoroughly discusses various hydrogel-based actuators responsive to solute/solvent variations, pH, chemical reactions, temperature, light, magnetic fields, electric fields, hydraulic/electro-osmotic stimuli, and humidity. It also details the strategies for designing and implementing diverse sensors, including strain, pressure, humidity, conductive, magnetic, thermal, gas, optical, and multimodal sensors. Finally, the paper offers an in-depth discussion of the prospective applications of hydrogel-based continuum soft robots, particularly emphasizing their potential in medical and industrial fields. Concluding remarks include a forward-looking outlook highlighting future challenges and promising research directions.

Advances in conducting nanocomposite hydrogels for wearable biomonitoring

Recent advancements in wearable biosensors and bioelectronics have led to innovative designs for personalized health management devices, with biocompatible conducting nanocomposite hydrogels emerging as a promising building block for soft electronics engineering. In this review, we provide a comprehensive framework for advancing biosensors using these engineered nanocomposite hydrogels, highlighting their unique properties such as high electrical conductivity, flexibility, self-healing, biocompatibility, biodegradability, and tunable architecture, broadening their biomedical applications. We summarize key properties of nanocomposite hydrogels for thermal, biomechanical, electrophysiological, and biochemical sensing applications on the human body, recent progress in nanocomposite hydrogel design and synthesis, and the latest technologies in developing flexible and wearable devices. This review covers various sensor types, including strain, physiological, and electrochemical sensors, and explores their potential applications in personalized healthcare, from daily activity monitoring to versatile electronic skin applications. Furthermore, we highlight the blueprints of design, working procedures, performance, detection limits, and sensitivity of these soft devices. Finally, we address challenges, prospects, and future outlook for advanced nanocomposite hydrogels in wearable sensors, aiming to provide a comprehensive overview of their current state and future potential in healthcare applications.

A Comprehensive Review on Novel Lipid-Based Nano Drug Delivery

Novel drug delivery system opens the doors towards nano/micro formulation strategies to overcome the challenges associated with the poorly soluble and permeable drugs. Lipid based nanoparticles are widely accepted that includes liposomes, niosomes and micelles which are FDA approved. Such lipid based drug delivery allows delivery for natural phytoconstituents, biopharmaceutical classification system (BCS) class II and class IV drugs are effectively delivered to improve its solubility, permeability and bioavailability. The article provides the recent advances and application of lipid based dosage form for improvement of therapeutic efficacy.

Electroconductive Collagen-Carbon Nanodots Nanocomposite Elicits Neurite Outgrowth, Supports Neurogenic Differentiation and Accelerates Electrophysiological Maturation of Neural Progenitor Spheroids

Neuronal disorders are characterized by the loss of functional neurons and disrupted neuroanatomical connectivity, severely impacting the quality of life of patients. This study investigates a novel electroconductive nanocomposite consisting of glycine-derived carbon nanodots (GlyCNDs) incorporated into a collagen matrix and validates its beneficial physicochemical and electro-active cueing to relevant cells. To this end, this work employs mouse induced pluripotent stem cell (iPSC)-derived neural progenitor (NP) spheroids. The findings reveal that the nanocomposite markedly augmented neuronal differentiation in NP spheroids and stimulate neuritogenesis. In addition, this work demonstrates that the biomaterial-driven enhancements of the cellular response ultimately contribute to the development of highly integrated and functional neural networks. Lastly, acute dizocilpine (MK-801) treatment provides new evidence for a direct interaction between collagen-bound GlyCNDs and postsynaptic N-methyl-D-aspartate (NMDA) receptors, thereby suggesting a potential mechanism underlying the observed cellular events. In summary, the findings establish a foundation for the development of a new nanocomposite resulting from the integration of carbon nanomaterials within a clinically approved hydrogel, toward an effective biomaterial-based strategy for addressing neuronal disorders by restoring damaged/lost neurons and supporting the reestablishment of neuroanatomical connectivity.

Flexible Silica/MXene/Natural rubber film strain sensors with island chain structure for Healthcare monitoring

The demand for flexible strain sensors with high sensitivity and durability has increased significantly. However, traditional sensors are limited in terms of their detection ranges and fabrications. In this work, a space stacking method was proposed to fabricate natural rubber (NR)/ Ti3C2Tx (MXene)/silica (SiO2) films that possessed exceptional electrical conductivity, sensitivity and reliability. The introduction of SiO2 into the NR/MXene composite enabled the construction of an "island-chain structure", which promoted the formation of conductive pathways and significantly improved the conductivity of the composite. Specifically, the electrical conductivity of the NR/MXene/10 wt%SiO2 composite was enhanced by about 200 times compared to that of the NR/MXene composite alone (from 0.07 to 13.4 S/m). Additionally, the "island-chain structure" further enhanced the sensing properties of the NR/MXene/10 wt%SiO2 composite, as evidenced by its excellent sensitivity (GF = 189.2), rapid response time (102 ms), and good repeatability over 10,000 cycles. The fabricated device demonstrates an outstanding mechanical sensing performance and can accurately detect human physiological signals. Specifically, the device serves as a strain detector, recognizing different strain signals by monitoring the movement of fingers, arms, and thighs. This study provides critical insights into composite manufacturing with exceptional conductivity, flexibility and stability, which are essential properties for creating high-performance flexible sensors.

High-Performing Conductive Hydrogels for Wearable Applications

Conductive hydrogels have gained significant attention for their extensive applications in healthcare monitoring, wearable sensors, electronic devices, soft robotics, energy storage, and human-machine interfaces. To address the limitations of conductive hydrogels, researchers are focused on enhancing properties such as sensitivity, mechanical strength, electrical performance at low temperatures, stability, antibacterial properties, and conductivity. Composite materials, including nanoparticles, nanowires, polymers, and ionic liquids, are incorporated to improve the conductivity and mechanical strength. Biocompatibility and biosafety are emphasized for safe integration with biological tissues. Conductive hydrogels exhibit unique properties such as stretchability, self-healing, wet adhesion, anti-freezing, transparency, UV-shielding, and adjustable mechanical properties, making them suitable for specific applications. Researchers aim to develop multifunctional hydrogels with antibacterial characteristics, self-healing capabilities, transparency, UV-shielding, gas-sensing, and strain-sensitivity.

Doped Carbon Quantum Dots Reinforced Hydrogels for Sustained Delivery of Molecular Cargo

Hydrogels have emerged as important soft materials with numerous applications in fields including biomedicine, biomimetic smart materials, and electrochemistry. Because of their outstanding photo-physical properties and prolonged colloidal stability, the serendipitous findings of carbon quantum dots (CQDs) have introduced a new topic of investigation for materials scientists. CQDs confined polymeric hydrogel nanocomposites have emerged as novel materials with integrated properties of the individual constituents, resulting in vital uses in the realm of soft nanomaterials. Immobilizing CQDs within hydrogels has been shown to be a smart tactic for preventing the aggregation-caused quenching effect and also for manipulating the characteristics of hydrogels and introducing new properties. The combination of these two very different types of materials results in not only structural diversity but also significant improvements in many property aspects, leading to novel multifunctional materials. This review covers the synthesis of doped CQDs, different fabrication techniques for nanostructured materials made of CQDs and polymers, as well as their applications in sustained drug delivery. Finally, a brief overview of the present market and future perspectives are discussed.

Water-Tolerant MXene Epidermal Sensors with High Sensitivity and Reliability for Healthcare Monitoring

Flexible and wearable pressure sensors have gained great popularity in consumer electronics due to their potential applications in human healthcare, E-skin, and artificial intelligence interactions. MXene is regarded as one of the most ideal candidate sensing materials due to its high electrical conductivity and controllable interlayer space. However, the easy-to-oxidize characteristic of MXene materials greatly restricts the sensitivity and reliability of sensor devices, especially in wet climates. Herein, a highly sensitive and waterproof flexible pressure sensor using a free-standing hydrophobic bacterial cellulose/Ti₃C₂T_x MXene (HBT) hybrid film as a sensing layer is fabricated by facile and effective nanocellulose intercalation and fluorine modification strategies. The obtained pressure sensor delivers high sensitivity (65.5 kPa^-1), fast response (50 ms), wide linear sensing range (0.002-30 kPa) with a low detection limit of 0.57 Pa, and excellent repeatability over 50,000 cycles. Meanwhile, owing to the highly hydrophobic surface of the HTB film, the outstanding sensing features could be well retained, although immersed in water several times. Benefiting from the excellent sensing properties and water resistance, the HBT sensor serves as a wearable force sensor to monitor the full-range human physiological motions regardless of whether the conditions are normal or wet. This work provides a new pathway to design the MXene pressure sensor with high reliability and demonstrates the promising usage of HBT sensors in portable biomedical electronics.

Stretchable, self-healing and adhesive sodium alginate-based composite hydrogels as wearable strain sensors for expansion-contraction motion monitoring

Developing multifunctional hydrogels with stretchability, self-healing ability, adhesiveness, and conductivity into flexible strain sensors for human motion and health monitoring has attracted great attention and is highly desired. However, the present motion detectors mainly focus on stretching, bending, and twisting of different body parts while the expansion-contraction motion has been rarely investigated. In this study, along with carbon nanotubes (CNTs) as conductive components, sodium alginate (Alg) modified with 3-aminophenylboronic acid (PBA) and dopamine (DA) were synthesized and employed as precursors to prepare a multifunctional Alg-CNT hydrogel. The formed dynamic covalent bonds between PBA and DA endowed the hydrogel with a rapid self-healing property (30 s) while the introduction of CNTs remarkably enhanced the mechanical strength and electrical conductivity of the hydrogel. Moreover, the as-prepared hydrogel displayed a satisfactory stretchability (500%) and self-adhesiveness to various substrates. When used as a strain sensor, the Alg-CNT hydrogel that exhibited a fast response (150 ms) and ultra-durability (over 30 000 cycles) was demonstrated to be capable of monitoring subtle expansion-contraction motions (e.g., human breathing and mouse heart beating) via periodic and repeatable electrical signals. Therefore, this multifunctional hydrogel is highly suitable for monitoring expansion-contraction motions, indicating its potential applications in personal health monitoring.

Gelator-Enhanced Organohydrogels with Switchable Mechanics and High-Strain Shape-Memory Capacity

Hydrogels and organogels, as two crucial representatives of soft materials, have attracted immense interest. However, they develop independently along two parallel lines, and these gels with single networks have their inherent drawbacks. For example, hydrogels tend to freeze, and organogels are usually brittle. Herein, organogels were incorporated into a hydrogel matrix for the synthesis of organohydrogels GOHs through polymerization in Pickering emulsion. The rigid organogel domains contribute to enhancing the strength of organohydrogels. Besides this, the organogels derived from 12-HAS self-assembly behavior exhibit a gel-sol transition when the temperature reaches 70 °C, thus leading to a thermo-softening behavior in the GOHs. Due to the phase transition of organogel domains and the elastic hydrogel network, the resultant organohydrogels demonstrate high-strain shape-memory performance (over 1000%) which could help achieve full recovery in seconds. Consequently, GOHs are endowed with the potential of practical application in soft robots, wearable devices, and biological materials.