Miniaturized Piezo Force Sensor for a Medical Catheter and Implantable Device

Piezoelectric PVDF and its copolymers in biomedicine: innovations and applications

In recent years, poly(vinylidene fluoride) (PVDF) has emerged as a versatile polymer with a wide range of applications across various fields. PVDF's piezosensitivity, versatility, crystalline structure, and tunable parameters have established it as a highly sought-after material. Furthermore, PVDF and its copolymers exhibit excellent processability and chemical resistance to a diverse array of substances. Of particular significance is its remarkable structural stability in physiological media, which highlights its potential for use in the development of biomedical products. This review offers a comprehensive overview of the latest advancements in PVDF-based biomedical systems. It examines the fabrication of stimulus-responsive delivery systems, bioelectric therapy devices, and tissue-regenerating scaffolds, all of which harness the piezosensitivity of PVDF. Moreover, the potential of PVDF in the fabrication of both invasive and non-invasive diagnostic tools is investigated, with particular emphasis on its flexibility, transparency, and piezoelectric efficiency. The material's high biocompatibility and physiological stability are of paramount importance in the development of implantable sensors for long-term health monitoring, which is crucial for the management of chronic diseases and postoperative care. Additionally, we discuss a novel approach to photoacoustic microscopy that employs a PVDF sensor, thereby eliminating the necessity for external contrast agents. This technique provides a new avenue for non-invasive imaging in biomedical applications. Finally, we explore the challenges and prospects for the development of PVDF-based systems for a range of biomedical applications. This review is distinctive in comparison to other reviews on PVDF due to its concentrated examination of biomedical applications, including pioneering imaging techniques, long-term health monitoring, and a detailed account of advancements in the field. Collectively, these elements illustrate the potential of PVDF to markedly influence biomedical engineering and patient care, distinguishing it from existing literature. By leveraging the distinctive attributes of PVDF and its copolymers, researchers can continue to advance the frontiers of biomedical engineering, with the potential to transform patient care and treatment outcomes.

The development and testing of a smart sensorized guide wire for catheterization in a "blood" vessel phantom to support aortic valve implementation

PURPOSE

Heart valve disease is commonly treated by minimally invasive procedures with guide wires and catheterization. The main purpose of this study is to find out whether an extension of the guide wire with a sensor can support the surgeon within the blood vessel to reduce X-ray necessity.

METHODS

A smart guide wire is developed by an extension with a flex-bending sensor to evaluate the sensor signal with and without "blood" flow at a constant compression force. Various surgically relevant investigations are performed. For assessment, the mean temporal average of the moving averaged filtered ADC signal and a subsequent FFT are carried out.

RESULTS

Results show that there is a smaller sensor signal when the applied force or bending at the sensor is higher. In all investigations, there was a different sensor signal. The flex-bending sensor can detect the effect of pulsatile flow. The smallest temporal averaged signal difference between reference and clamp in the front wire's tip is 1.09%. For example, the mean temporal average of the filtered ADC signal for different clinically relevant scenarios is between 2550 and 2900.

CONCLUSIONS

The results show that the sensorized guide wire developed for catheterization can support aortic valve implementation. The sensor sensitivity is sufficient to detect even very small variations within the blood vessel and therefore is promising to support catheterization heart valve surgeries in future.

Smart Hydrogel Swelling State Detection Based on a Power-Transfer Transduction Principle

Stimulus-responsive (smart) hydrogels are a promising sensing material for biomedical contexts due to their reversible swelling change in response to target analytes. The design of application-specific sensors that utilize this behavior requires the development of suitable transduction concepts. The presented study investigates a power-transfer-based readout approach that is sensitive to small volumetric changes of the smart hydrogel. The concept employs two thin film polyimide substrates with embedded conductive strip lines, which are shielded from each other except at the tip region, where the smart hydrogel is sandwiched in between. The hydrogel's volume change in response to a target analyte alters the distance and orientation of the thin films, affecting the amount of transferred power between the two transducer parts and, consequently, the measured sensor output voltage. With proper calibration, the output signal can be used to determine the swelling change of the hydrogel and, consequently, to quantify the stimulus. In proof-of-principle experiments with glucose- and pH-sensitive smart hydrogels, high sensitivity to small analyte concentration changes was found along with very good reproducibility and stability. The concept was tested with two exemplary hydrogels, but the transduction principle in general is independent of the specific hydrogel material, as long as it exhibits a stimulus-dependent volume change. The application vision of the presented research is to integrate in situ blood analyte monitoring capabilities into standard (micro)catheters. The developed sensor is designed to fit into a catheter without obstructing its normal use and, therefore, offers great potential for providing a universally applicable transducer platform for smart catheter-based sensing.

A Review of Recent Advancements in Sensor-Integrated Medical Tools

A medical tool is a general instrument intended for use in the prevention, diagnosis, and treatment of diseases in humans or other animals. Nowadays, sensors are widely employed in medical tools to analyze or quantify disease-related parameters for the diagnosis and monitoring of patients' diseases. Recent explosive advancements in sensor technologies have extended the integration and application of sensors in medical tools by providing more versatile in vivo sensing capabilities. These unique sensing capabilities, especially for medical tools for surgery or medical treatment, are getting more attention owing to the rapid growth of minimally invasive surgery. In this review, recent advancements in sensor-integrated medical tools are presented, and their necessity, use, and examples are comprehensively introduced. Specifically, medical tools often utilized for medical surgery or treatment, for example, medical needles, catheters, robotic surgery, sutures, endoscopes, and tubes, are covered, and in-depth discussions about the working mechanism used for each sensor-integrated medical tool are provided.

One Novel Hybrid Flexible Piezoresistive/Piezoelectric Double-Mode Sensor Design for Water Leakage Monitoring

Water leakage is a significant issue in infrastructure, such as submarine tunnels, which can lead to major disasters and property losses. Therefore, it is of great significance to develop a water leakage detection sensor with simple preparation process, low cost, and small limitation of applicable location. In this study, a novel hybrid flexible piezoresistive/piezoelectric double-mode sensor with a sandpaper negative microstructure is proposed. A unique dual-path perception structure is designed that can simultaneously and independently detect two signals of water leakage frequency and water leakage volume. The piezoresistive layer is formed by polydimethylsiloxane (PDMS) coated with multiwalled carbon nanotubes (MWCNTs), which is molded by sandpaper molding. By sensing the deformation caused by the swelling of superabsorbent polymers (SAPs), the water leakage volume can be detected as low as 0.5 mL. The piezoelectric layer is a polyvinylidene fluoride-trifluoroethylene copolymer (PVDF-TrFE) film prepared by the spin-coating method, and the water leakage frequency (0.5-4 Hz) is detected by direct contact with water droplets. This work also studied the performance of the double-mode sensor under low temperature and seawater leakage conditions and further verified its reliability in different environments. The design of the new hybrid flexible piezoresistive/piezoelectric double-mode sensor provides a new possibility for water leakage monitoring, such as in submarine tunnels.

Advanced medical micro-robotics for early diagnosis and therapeutic interventions

Recent technological advances in micro-robotics have demonstrated their immense potential for biomedical applications. Emerging micro-robots have versatile sensing systems, flexible locomotion and dexterous manipulation capabilities that can significantly contribute to the healthcare system. Despite the appreciated and tangible benefits of medical micro-robotics, many challenges still remain. Here, we review the major challenges, current trends and significant achievements for developing versatile and intelligent micro-robotics with a focus on applications in early diagnosis and therapeutic interventions. We also consider some recent emerging micro-robotic technologies that employ synthetic biology to support a new generation of living micro-robots. We expect to inspire future development of micro-robots toward clinical translation by identifying the roadblocks that need to be overcome.

Functionality of Flexible Pressure Sensors in Cardiovascular Health Monitoring: A Review

As the highest percentage of global mortality is caused by several cardiovascular diseases (CVD), maintenance and monitoring of a healthy cardiovascular condition have become the primary concern of each and every individual. Simultaneously, recent progress and advances in wearable pressure sensor technology have provided many pathways to monitor and detect underlying cardiovascular illness in terms of irregularities in heart rate, blood pressure, and blood oxygen saturation. These pressure sensors can be comfortably attached onto human skin or can be implanted on the surface of vascular grafts for uninterrupted monitoring of arterial blood pressure. While the traditional monitoring systems are time-consuming, expensive, and not user-friendly, flexible sensor technology has emerged as a promising and dynamic practice to collect important health information at a comparatively low cost in a reliable and user-friendly way. This Review explores the importance and necessity of cardiovascular health monitoring while emphasizing the role of flexible pressure sensors in monitoring patients' health conditions to avoid adverse effects. A comprehensive discussion on the current research progress along with the real-time impact and accessibility of pressure sensors developed for cardiovascular health monitoring applications has been provided.

Phone Camera Nano-Biosensor Using Mighty Sensitive Transparent Reusable Upconversion Paper

Lycopene, a natural colorant and antioxidant with a huge growing market, is highly susceptible to photo/thermal degradation, which demands real-time sensors. Hence, here a transparent upconversion nanoparticles (UCNPs) strip having 30 mol % Yb, 0.1 mol % Tm, and β-NaYF4 UCNPs, which shows an intense emission at 475 nm, has been developed. This strip has been found to be sensitive to lycopene with a detection limit as low as 10 nM using a smartphone camera, which is due to static quenching that is confirmed by the lifetime study. In comparison to previous paper strips, here the transparent strip has minimal scattering with maximum sensitivity in spite of not using any metal quenchers. An increase in strip hydrophobicity during the fabrication process complements the strip to selectively permeate and present an extraction-free substitute analysis for chromatography. Hydrophobicity endows the strip with the capability to reuse the strip with ∼100% luminescence recovery.

Smart implanted access port catheter for therapy intervention with pH and lactate biosensors

Totally implanted access ports (TIAP) are widely used with oncology patients requiring long term central venous access for the delivery of chemotherapeutic agents, infusions, transfusions, blood sample collection and parenteral nutrition. Such devices offer a significant improvement to the quality of life for patients and reduced complication rates, particularly infection, in contrast to the classical central venous catheters. Nevertheless, infections do occur, with biofilm formation bringing difficulties to the treatment of infection-related complications that can ultimately lead to the explantation of the device. A smart TIAP device that is sensor-enabled to detect infection prior to extensive biofilm formation would reduce the cases for potential device explantation, whereas biomarkers detection within body fluids such as pH or lactate would provide vital information regarding metabolic processes occurring inside the body. In this paper, we propose a novel batteryless and wireless device suitable for the interrogation of such markers in an embodiment model of an TIAP, with miniature biochemical sensing needles. Device readings can be carried out by a smartphone equipped with Near Field Communication (NFC) interface at relative short distances off-body, while providing radiofrequency energy harvesting capability to the TIAP, useful for assessing patient's health and potential port infection on demand.

Ultrasound-Powered Implants: A Critical Review of Piezoelectric Material Selection and Applications

Ultrasound-powered implants (UPIs) represent cutting edge power sources for implantable medical devices (IMDs), as their powering strategy allows for extended functional lifetime, decreased size, increased implant depth, and improved biocompatibility. IMDs are limited by their reliance on batteries. While batteries proved a stable power supply, batteries feature relatively large sizes, limited life spans, and toxic material compositions. Accordingly, energy harvesting and wireless power transfer (WPT) strategies are attracting increasing attention by researchers as alternative reliable power sources. Piezoelectric energy scavenging has shown promise for low power applications. However, energy scavenging devices need be located near sources of movement, and the power stream may suffer from occasional interruptions. WPT overcomes such challenges by more stable, on-demand power to IMDs. Among the various forms of WPT, ultrasound powering offers distinct advantages such as low tissue-mediated attenuation, a higher approved safe dose (720 mW cm^-2 ), and improved efficiency at smaller device sizes. This study presents and discusses the state-of-the-art in UPIs by reviewing piezoelectric materials and harvesting devices including lead-based inorganic, lead-free inorganic, and organic polymers. A comparative discussion is also presented of the functional material properties, architecture, and performance metrics, together with an overview of the applications where UPIs are being deployed.

A Hybrid Microstructure Piezoresistive Sensor with Machine Learning Approach for Gesture Recognition

Developments in flexible electronics have adopted various approaches which have enhanced the applicability of human–machine interface fields. Recently, microstructural integration and hybrid functional materials were designed for realizing human somatosensory. Nonetheless, designing tactile sensors with smart structures using facile and low-cost fabrication processes remains challenging. Furthermore, using the sensors for recognizing stimuli and feedback applications remains poorly validated. In this study, a highly flexible piezoresistive tactile sensor was developed by homogeneously dispersing carbon black (CB) in a microstructure porous sugar/PDMS-based sponge. Owning to its high flexibility and softness, the sensor can be mounted on human or robotic systems for different clinical applications. We validated the applicability of the proposed sensor by applying it to recognizing grasp and release forces in an open setting and to classifying hand motions that surgeons apply on the master interface of a robotic system during intravascular catheterization. For this purpose, we implemented the long short-term memory (LSTM)-dense classification model and five traditional machine learning methods, namely, support vector machine, multilayer perceptron, decision tree, and k-nearest neighbor. The models were used to classify the different hand gestures obtained in an open-setting experiment. Amongst all, the LSTM-dense method yielded the highest overall recognition accuracy (87.38%). Nevertheless, the performance of the other models was in a similar range, showing that our sensor structure can be applied in intelligence sensing or tactile feedback systems. Secondly, the sensor prototype was applied to analyze the motions made while manipulating an interventional robot. We analyzed the displacement and velocity of the master interface during typical axial (push/pull) and radial operations with the robot. The results obtained show that the sensor is capable of recording unique patterns during different operations. Thus, a combination of the flexible wearable sensors and machine learning could yield a future generation of flexible materials and artificial intelligence of things (AIoT) devices.

Progress on Self-Powered Wearable and Implantable Systems Driven by Nanogenerators

With the rapid development of the internet of things (IoT), sustainable self-powered wireless sensory systems and diverse wearable and implantable electronic devices have surged recently. Under such an opportunity, nanogenerators, which can convert continuous mechanical energy into usable electricity, have been regarded as one of the critical technologies for self-powered systems, based on the high sensitivity, flexibility, and biocompatibility of piezoelectric nanogenerators (PENGs) and triboelectric nanogenerators (TENGs). In this review, we have thoroughly analyzed the materials and structures of wearable and implantable PENGs and TENGs, aiming to make clear how to tailor a self-power system into specific applications. The advantages in TENG and PENG are taken to effectuate wearable and implantable human-oriented applications, such as self-charging power packages, physiological and kinematic monitoring, in vivo and in vitro healing, and electrical stimulation. This review comprehensively elucidates the recent advances and future outlook regarding the human body's self-powered systems.

Mortise-tenon joint structured hydrophobic surface-functionalized barium titanate/polyvinylidene fluoride nanocomposites for printed self-powered wearable sensors

Self-powered wearable sensors exhibiting high sensitivity and flexibility have attracted widespread interest in the field of wearable electronics. Herein, a 3D printing technique was employed to fabricate a fully printed, flexible self-powered sensor with high piezoelectric performance. This printing technique is based on the hydrophobic surface-functionalized barium titanate (FD-BTO)/polyvinylidene fluoride (PVDF) composite film. To strengthen the interface bond between BTO and PVDF, the BTO nanoparticles were surface functionalized using hydrophobic 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES). As a result, there was an increase in the content of the β-phase in the PFDTES modified BTO (FD-BTO) nanoparticle composite film. The 3D-printed self-powered sensor based on the optimum FD-BTO/PVDF composite film exhibited excellent sensitivity (61.6 mV kPa-1) with a piezoelectric coefficient (d33) of 69.1 pC/N, which is two-fold higher than that of the unfunctionalized BTO/PVDF counterpart. Additionally, the power sensor displayed excellent mechanical durability in the 20 000 cyclic force tests. In practice, the printed devices were used as a sports wearable device to monitor and analyze athlete motion, and a self-powered printed sensor array (5 × 5), which could effectively detect the pattern image of the external pressure input. The 3D-printed self-powered sensor demonstrated herein can contribute significantly to the applications and the development of printed electronic wearable devices.