Multifunctional Siloxene-Decorated Laser-Inscribed Graphene Patch for Sweat Ion Analysis and Electrocardiogram Monitoring.

Potentiometric detection in complex biological fluids enables continuous electrolyte monitoring for personal healthcare; however, the commercialization of ion-selective electrode-based devices has been limited by the rapid loss of potential stability caused by electrode surface inactivation and biofouling. Here, we describe a simple multifunctional hybrid patch incorporating an Au nanoparticle/siloxene-based solid contact (SC) supported by a substrate made of laser-inscribed graphene on poly(dimethylsiloxane) for the noninvasive detection of sweat Na+ and K+. These SC nanocomposites prevent the formation of a water layer during ion-to-electron transfer, preserving 3 and 5 µV/h potential drift for the Na+ and K+ ion-selective electrodes, respectively, after 13 h of exposure. The lamellar structure of the siloxene sheets increases the SC area. In addition, the electroplated Au nanoparticles, which have a large surface area and excellent conductivity, further increased the electric double-layer capacitance at the interface between the ion-selective membranes and solid-state contacts, thus facilitating ion-to-electron transduction and ultimately improving the detection stability of Na+ and K+. Furthermore, the integrated temperature and electrocardiogram sensors in the flexible patch assist in monitoring body temperature and electrocardiogram signals, respectively. Featuring both electrochemical ion-selective and physical sensors, this patch offers immense potential for the self-monitoring of health.

Reduced graphene oxide-functionalized polymer microneedle for continuous and wide-range monitoring of lactate in interstitial fluid.

Despite substantial developments in minimally invasive lactate monitoring microneedle electrodes, most such electrode developments have focused on either sensitivity or invasiveness while ignoring a wide range of detection, which is the most important factor in measuring the normal range of lactate in interstitial fluid (ISF). Herein, we present a polymer-based planar microneedle electrode fabrication using microelectromechanical and femtosecond laser technology for the continuous monitoring of lactate in ISF. The microneedle is functionalized with two-dimensional reduced graphene oxide (rGO) and electrochemically synthesized platinum nanoparticles (PtNPs). A particular quantity of Nafion (1.25 wt%) is applied on top of the lactate enzyme to create a diffusion-controlled membrane. Due to the combined effects of the planar structure of the microneedle, rGO, and membrane, the biosensor exhibited excellent linearity up to 10 mM lactate with a limit of detection of 2.04 µM, high sensitivity of 43.96 µA mM-1cm-2, a reaction time of 8 s and outstanding stability, selectivity, and repeatability. The feasibility of the microneedle is evaluated by using it to measure lactate concentrations in artificial ISF and human serum. The results demonstrate that the microneedle described here has great potential for use in real-time lactate monitoring for use in sports medicine and treatment.

Microfluidic-Integrated Multimodal Wearable Hybrid Patch for Wireless and Continuous Physiological Monitoring.

Despite extensive advances in wearable monitoring systems, most designs focus on the detection of physical parameters or metabolites and do not consider the integration of microfluidic channels, miniaturization, and multimodality. In this study, a combination of multimodal (biochemical and electrophysiological) biosensing and microfluidic channel-integrated patch-based wireless systems is designed and fabricated using flexible materials for improved wearability, ease of operation, and real-time and continuous monitoring. The reduced graphene oxide-based microfluidic channel-integrated glucose biosensor exhibits a good sensitivity of 19.97 (44.56 without fluidic channels) µA mM-1 cm-2 within physiological levels (10 µM-0.4 mM) with good long-term and bending stability. All the sensors in the patch are initially validated using sauna gown sweat-based on-body and real-time tests with five separate individuals who perspired three times each. Multimodal glucose and electrocardiogram (ECG) sensing, along with their real-time adjustment based on sweat pH and temperature fluctuations, optimize sensing accuracy. Laser-burned hierarchical MXene-polyvinylidene fluoride-based conductive carbon nanofiber-based dry ECG electrodes exhibit low skin contact impedance (40.5 kΩ cm2) and high-quality electrophysiological signals (signal-to-noise ratios = 23.4-32.8 dB). The developed system is utilized to accurately and wirelessly monitor the sweat glucose and ECG of a human subject engaged in physical exercise in real time.

Stretchable and All-Directional Strain-Insensitive Electronic Glove for Robotic Skins and Human-Machine Interfacing.

Electronic gloves (e-gloves), with their multifunctional sensing capability, hold a promising application in robotic skin and human-machine interfaces, endowing robots with a human sense of touch. Despite the progress in developing e-gloves by exploiting flexible or stretchable sensors, existing models have inherent rigidity in their sensing area, limiting their stretchability and sensing performance. Herein, we present an all-directional strain-insensitive stretchable e-glove that successfully extends sensing functionality such as pressure, temperature, humidity, and ECG with minimal crosstalk. A scalable and facile method is successfully demonstrated by combining low-cost CO2 laser engraving and electrospinning technology to fabricate multimodal e-glove sensors with a vertical architecture. In comparison to other smart gloves, the proposed e-glove features a ripple-like meandering sensing area and interconnections that are designed to stretch in response to the applied deformation, without affecting the performance of the sensors offering full mechanical stretchability. Furthermore, CNT-coated laser-engraved graphene (CNT/LEG) is used as an active sensing material in which the cross-linking network of the CNT in the LEG minimizes the stress effect and maximizes the sensitivity of the sensors. The fabricated e-glove can detect hot/cold, moisture, and pain simultaneously and precisely, while also allowing for remote transmission of sensory data to the user.

Highly Sensitive and Reliable Piezoresistive Strain Sensor Based on Cobalt Nanoporous Carbon-Incorporated Laser-Induced Graphene for Smart Healthcare Wearables.

The development of highly sensitive, reliable, and cost-effective strain sensors is a big challenge for wearable smart electronics and healthcare applications, such as soft robotics, point-of-care systems, and electronic skins. In this study, we newly fabricated a highly sensitive and reliable piezoresistive strain sensor based on polyhedral cobalt nanoporous carbon (Co-NPC)-incorporated laser-induced graphene (LIG) for wearable smart healthcare applications. The synergistic integration of Co-NPC and LIG enables the performance improvement of the strain sensor by providing an additional conductive pathway and robust mechanical properties with a high surface area of Co-NPC nanoparticles. The proposed porous graphene nanosheets exploited with Co-NPC nanoparticles demonstrated an outstanding sensitivity of 1,177 up to a strain of 18%, which increased to 39,548 beyond 18%. Additionally, the fabricated sensor exhibited an ultralow limit of detection (0.02%) and excellent stability over 20,000 cycles even under high strain conditions (10%). Finally, we successfully demonstrated and evaluated the sensor performance for practical use in healthcare wearables by monitoring wrist pulse, neck pulse, and joint flexion movement. Owing to the outstanding performance of the sensor, the fabricated sensor has great potential in electronic skins, human-machine interactions, and soft robotics applications.

A hybridized nano-porous carbon reinforced 3D graphene-based epidermal patch for precise sweat glucose and lactate analysis.

Wearable electrochemical biosensors for perspiration analysis offer a promising non-invasive biomarker monitoring method. Herein, a functionalized hybridized nanoporous carbon (H-NPC)-encapsulated flexible 3D porous graphene-based epidermal patch was firstly fabricated for monitoring sweat glucose, lactate, pH, and temperature using simple, cost-effective, laser-engraved, and spray-coating techniques. The fabricated H-NPC-modified electrode significantly increased electrochemical surface area and electrocatalytic activity. Within the physiological sweat range (0-1.5 mM), the second-generation glucose sensor exhibited an excellent sensitivity of 82.7 µAmM-1cm-2 with 0.025 µM LOD. Moreover, the lactate biosensor exhibited an extraordinary linear range (0-56 mM) response owing to the incorporation of an outer diffusion limiting layer (DLL) that controls the lactate flux reaching the enzyme with comparable sensitivity (204 nAmM-1cm-2) and LOD (4 µM). Finally, we employed an analytical correction approach incorporating pH and temperature adjustments during on-body tests. In addition to connecting various carbon-based materials to limitless metal-organic frameworks as a transduction material, our research also paves the way for enabling these sensors to operate on pH and T correction independently while delivering accurate results.

Hysteresis-Free Double-Network Hydrogel-Based Strain Sensor for Wearable Smart Bioelectronics.

Hydrogel-based electronics have attracted substantial attention in the field of biological engineering, energy storage devices, and soft actuators due to their resemblance to living tissues, biocompatibility, tunable softness, and consolidated structures. However, combining the properties of quick resilience, hysteresis-free, and robust mechanical properties in physically cross-linked hydrogels is still a great challenge. Herein, we present a vinyl hybrid silica nanoparticle (VSNPs)/polyacrylamide (PAAm)/alginate double-network hydrogel-based strain sensor with the characteristics of quick resilience, hysteresis-free, and a low limit of detection (LOD). The physical cross-linking among PAAm chains and covalent cross-linking between PAAm, alginate, and N,N-methylenebisacrylamide chains promotes excellent mechanical properties. Moreover, the incorporation of VSNPs reinforces the mechanical strength by the dynamic cross-linking of the PAAm network to maintain the integrity of the hydrogel and works as a stress buffer to dissipate energy. The as-prepared hydrogel-based sensor exhibits a strain sensitivity (i.e., gauge factor) of 1.73 (up to 100% strain), a response time of 0.16 s, an ultra-low electrical hysteresis of 2.43%, and a low LOD of 0.4%. The outstanding properties of the hydrogel are further used to illustrate the utility of the sensor in e-skin, ranging from low-strain applications, such as carotid pulse and artificial sound detection, to large bending applications, such as sign language translations. In addition, an efficient and cost-effective synthesis of double-network hydrogel that can overcome the bottleneck of the electromechanical properties of single network hydrogel has potential prospects in soft actuators, tissue engineering, and various biomedical applications.

A nanocomposite-decorated laser-induced graphene-based multi-functional hybrid sensor for simultaneous detection of water contaminants.

Here, nanocomposite-decorated laser-induced graphene-based flexible hybrid sensor is newly developed for simultaneous detection of heavy metals, pesticides, and pH in freshwater. A series of deposition methods such as drop-casting, electroplating, and heating are adopted to modify and functionalize laser-induced graphene for engineering the high-performance detection at the individual sensor. A micro-dendritic structured bismuth@tin alloy inlaid on laser-induced graphene is prepared via a simple ex-situ electrodeposition method and thermal treatment for detecting heavy metals. The electrochemical performance is evaluated through the simultaneous determination of lead and cadmium ions at the optimized deposition potential of -1.2 V for 170 s, and a wide detection concentration range of 2-250 ppb and low detection limits (1.6 ppb and 0.9 ppb, respectively) are achieved. The pesticide sensor co-modified by zirconia nanoparticles and multilayered Ti3C2Tx-MXene is successfully implemented with a good linear performance for parathion after an optimal accumulation time of 120s. It realizes a low detection concentration range (0.1-5 ppb) with a detection limit of 0.06 ppb. Furthermore, a polyaniline/antimony/laser-induced graphene-based pH sensor is also integrated, showing an excellent sensitivity of -72.08 mV pH-1 in the pH range (2-9). They are also measured and characterized in different real water samples, exhibiting an acceptable detection performance, which provides promising applicability in the on-site monitoring of pollutants in the water environment.

Siloxene-Functionalized Laser-Induced Graphene via COSi Bonding for High-Performance Heavy Metal Sensing Patch Applications.

Here, 2D Siloxene nanosheets are newly applied to functionalize porous laser-induced graphene (LIG) on polydimethylsiloxane, modify the surface chemical properties of LIG, and improve the heterogeneous electron transfer rate. Meanwhile, the newly generated COSi crosslink boosts the binding of LIG and Siloxene. Thus, the Siloxene/LIG composite is used as the basic electrode material for the multifunctional detection of copper (Cu) ions, pH, and temperature in human perspiration. Moreover, to enhance the sensing performance of Cu ions, Siloxene/LIG is further modified by carbon nanotubes (CNTs). The fabricated Siloxene-CNT/LIG-based Cu-ion sensor shows linear response within a wide range of 10-500 ppb and a low detection limit of 1.55 ppb. In addition, a pH sensor is integrated to calibrate for determining the accurate concentration of Cu ions due to pH dependency of the Cu-ion sensor. The polyaniline-deposited pH sensor demonstrates a good sensitivity of -64.81 mV pH-1 over the pH range of 3-10. Furthermore, a temperature sensor for accurate skin temperature monitoring is also integrated and exhibits a stable linear resistance response with an excellent sensitivity of 9.147 Ω °C-1 (correlation coefficient of 0.139% °C-1 ). The flexible hybrid sensor is promising in applications of noninvasive heavy-metal ion detection and prediction of related diseases.

Multifunctional hybrid skin patch for wearable smart healthcare applications.

Recent advances in wearable patches have included various sensors to monitor either physiological signs, such as the heart rate and respiration rate, or metabolites. Nevertheless, most of these have focused only on a single physiological measurement at a time, which significantly inhibits the calibration of various biological signals and diagnostic facilities. In this study, a novel multifunctional hybrid skin patch was developed for the electrochemical analysis of sweat glucose levels and simultaneous monitoring of electrocardiograms (ECGs). Furthermore, pH and temperature sensors were co-integrated onto the same patch for the calibration of the glucose biosensor to prevent inevitable inhibition and weakening of enzyme activity due to changes in the sweat pH and temperature levels. The fabricated electrochemical glucose biosensor exhibited excellent linearity (R2 = 0.9986) and sensitivity (29.10 µA mM-1 cm-2), covering the normal range of human sweat. The potentiometric pH sensor displayed a good response with an excellent sensitivity of -77.81 mV/pH and high linearity (R2 = 0.991), indicating that it can distinguish variations in the typical pH range for human sweat. Furthermore, the P, QRS complex, and T peaks in the measured ECG waveforms could be clearly distinguished, indicating the reliability of the fabricated flexible dry electrodes for continuous monitoring. The fabricated skin patch overcomes the inconvenience of the mandatory attachment of multiple patches on the human body by fully integrating all the electrochemical and electrophysiological sensors on a single patch, thus facilitating advanced glycemic control and continuous ECG monitoring for smart management of chronic diseases and healthcare applications.

A highly selective and stable cationic polyelectrolyte encapsulated black phosphorene based impedimetric immunosensor for Interleukin-6 biomarker detection.

Due to the insufficiency of binding sites for the immobilized recognition biomolecules on the immunosensing platform, cancer detection becomes challenging. Whereas, the degradation of black phosphorene (BP) in the presence of the environmental factors becomes a concerning issue for use in electrochemical sensing. In this study, BP is successfully encapsulated by polyallylamine (PAMI) to increase its stability as well as to enhance its electrochemical performance. The successful encapsulation of BP is ensured through X-ray Photoelectron spectroscopy and Raman spectroscopy, whereas the stability of black phosphorus is ensured by Zeta potential measurements and cyclic voltammetry tests. The developed BP-PAMI composite showed high stability in the ambient environment and exhibited improved electrochemical performances. The impedimetric immunosensor was developed on a BP-PAMI modified laser burned graphene (LBG) to detect interleukin-6 biomarkers using electrochemical impedance spectroscopy (EIS). Under the optimized parameters, the fabricated immunosensor demonstrated a wide linear range of 0.003-75 ng/mL, limit of detection (LOD) of 1 pg/mL. Based on the experimental analysis, the developed sensing strategy can be employed as an easy, disposable, cost-effective and highly selective point-of-care cancer detection. In addition, the developed technique can be applied broadly for detecting other biomarkers after treating with suitable biomolecules.

A rime ice-inspired bismuth-based flexible sensor for zinc ion detection in human perspiration.

A nature-inspired special structure of bismuth is newly presented as Zn ion sensing layer for high-performance electrochemical heavy metal detection sensor applications. The rime ice-like bismuth (RIBi) has been synthesized using an easy ex situ electrodeposition method on the surface of a flexible graphene-based electrode. The flexible graphene-based electrode was fabricated via simple laser-writing and substrate-transfer techniques. The Zn ion sensing performance of the proposed heavy metal sensor was evaluated by square wave anodic stripping voltammetry after investigating the effects of several parameters, such as preconcentration potential, preconcentration time, and pH of acetate buffer. The proposed RIBi-based heavy metal sensor demonstrated a good linear relationship between concentration and current in the range 100-1600 ppb Zn ions with an acceptable sensitivity of 106 nA/ppb·cm2. The result met the requirements in terms of common human perspiration levels (the average Zn ion concentration in perspiration is 800 ppb). In addition, the heavy metal sensor response to Zn ions was successfully performed in human perspiration samples as well, and the results were consistent with those measured by atomic absorption spectroscopy. Besides, the fabricated Zn ion sensor exhibited excellent selectivity, repeatability, and flexibility. Finally, a PANI-LIG-based pH sensor (measurement range: pH 4-7) was also integrated with the Zn ion sensor to form a single chip hybrid sensor. These results may provide a great possibility for the use of the proposed flexible sensor to realize wearable perspiration-based healthcare systems. Graphical abstract.

Electrospun PVDF-TrFE/MXene Nanofiber Mat-Based Triboelectric Nanogenerator for Smart Home Appliances.

Understanding of the triboelectric charge accumulation from the view of microcapacitor formation plays a critical role in boosting the output performance of the triboelectric nanogenerator (TENG). Here, an electrospun nanofiber-based TENG (EN-TENG) using a poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE)/MXene nanocomposite material with superior dielectric constant and high surface charge density is reported. The influence of dielectric properties on the output performance of the EN-TENG is investigated theoretically and experimentally. The fabricated EN-TENG exhibited a maximum power density of 4.02 W/m2 at a matching external load resistance of 4 MΩ. The PVDF-TrFE/MXene nanocomposite improved the output performance of the EN-TENG fourfold. The EN-TENG successfully powered an electronic stopwatch and thermo-hygrometer by harvesting energy from human finger tapping. Moreover, it was utilized in smart home applications as a self-powered switch for controlling electrical home appliances, including fire alarms, fans, and smart doors. This work presents an effective and innovative approach toward self-powered systems, human-machine interfaces, and smart home applications.

Hydrogen-Bond-Triggered Hybrid Nanofibrous Membrane-Based Wearable Pressure Sensor with Ultrahigh Sensitivity over a Broad Pressure Range.

Recently, flexible capacitive pressure sensors have received significant attention in the field of wearable electronics. The high sensitivity over a wide linear range combined with long-term durability is a critical requirement for the fabrication of reliable pressure sensors for versatile applications. Herein, we propose a special approach to enhance the sensitivity and linearity range of a capacitive pressure sensor by fabricating a hybrid ionic nanofibrous membrane as a sensing layer composed of Ti3C2Tx MXene and an ionic salt of lithium sulfonamides in a poly(vinyl alcohol) elastomer matrix. The reversible ion pumping triggered by a hydrogen bond in the hybrid sensing layer leads to high sensitivities of 5.5 and 1.5 kPa-1 in the wide linear ranges of 0-30 and 30-250 kPa, respectively, and a fast response time of 70.4 ms. In addition, the fabricated sensor exhibits a minimum detection limit of 2 Pa and high durability over 20 000 continuous cycles even under a high pressure of 45 kPa. These results indicate that the proposed sensor can be potentially used in mobile medical monitoring devices and next-generation artificial e-skin.

A wearable battery-free wireless and skin-interfaced microfluidics integrated electrochemical sensing patch for on-site biomarkers monitoring in human perspiration.

In this study, an ultra-high sensitive, flexible, wireless, battery-free, and fully integrated (no external analysis equipment) electrochemical sensing patch system, including a microfluidic-sweat collecting unit, was newly developed for the on-site monitoring of the [K+] concentration in human sweat. Multiwalled carbon nanotube (MWCNT) and MXene-Ti3C2TX based hybrid multi-dimensional networks were applied to obtain a high surface activation area and faster charge transfer rate, strongly adsorbing the valinomycin membrane to protect the ionophore for effective transshipment and immobilization of the [K+]. Furthermore, the controllable porosity of carbon-based materials can accelerate the kinetic process of ion diffusion. This hybrid nanonetwork structure effectively enhanced electrochemical stability and sensitivity, addressing the noise and signal drifting problems experienced with low concentration detection. The fabricated sensor exhibited a high ion concentration sensitivity of 63 mV/dec with excellent selectivity, amplified to 173 mV/dec with the integrated amplification system. The Near Field Communication (NFC) is used to transmit measurements to a smartphone wirelessly. A microfluidic channel was integrated with the electrochemical sensor patch to efficiently collect sweat on the human skin surface and mitigate the sensor surface contamination problem. Furthermore, the developed sensing patch can also be applied to other biomarkers on-site detection after modifying the working electrode with the corresponding selective membranes.

Smart bandage with integrated multifunctional sensors based on MXene-functionalized porous graphene scaffold for chronic wound care management.

Three-dimensional (3D) porous laser-guided graphene (LGG) electrodes on elastomeric substrates are of great significance for developing flexible functional electronics. However, the high sheet resistance and poor mechanical properties of LGG sheets obstruct their full exploitation as electrode materials. Herein, we applied 2D MXene nanosheets to functionalize 3D LGG sheets via a C-O-Ti covalent crosslink to obtain an LGG-MXene hybrid scaffold exhibited high conductivity and improved electrochemistry with fast heterogeneous electron transfer (HET) rate due to the synergistic effect between LGG and MXene. Then we transferred the obtained hybrid scaffold onto PDMS to engineer a smart, flexible, and stretchable multifunctional sensors-integrated wound bandage capable of assessing uric acid (UA), pH, and temperature at the wound site. The integrated UA sensor exhibited a rapid response toward UA in an extended wide range of 50-1200 µM with a high sensitivity of 422.5 µA mM-1 cm-2 and an ultralow detection limit of 50 µM. Additionally, the pH sensor demonstrated a linear Nernstian response (R2 = 0.998) with a high sensitivity of -57.03 mV pH-1 in the wound relevant pH range of 4-9. The temperature sensor exhibited a fast and stable linear resistive response to the temperature variations in the physiological range of 25-50 °C with an excellent sensitivity and correlation coefficient of 0.09% °C-1 and 0.999, respectively. We anticipate that this stretchable and flexible smart bandage could revolutionize wound care management and have profound impacts on the therapeutic outcomes.

High-Performance Flexible Electrochemical Heavy Metal Sensor Based on Layer-by-Layer Assembly of Ti3C2Tx/MWNTs Nanocomposites for Noninvasive Detection of Copper and Zinc Ions in Human Biofluids.

A flexible electrochemical heavy metal sensor based on a gold (Au) electrode modified with layer-by-layer (LBL) assembly of titanium carbide (Ti3C2Tx) and multiwalled carbon nanotubes (MWNTs) nanocomposites was successfully fabricated for the detection of copper (Cu) and zinc (Zn) ions. An LBL drop-coating process was adopted to modify the surface of Au electrodes with Ti3C2Tx/MWNTs treated via ultrasonication to fabricate this novel nanocomposite electrode. In addition, an in situ simultaneous deposition of "green metal" antimony (Sb) and target analytes was performed to improve the detection performance further. The electrochemical measurement was realized using square wave anodic stripping voltammetry (SWASV). Moreover, the fabricated sensor exhibited excellent detection performance under the optimal experimental conditions. The detection limits for Cu and Zn are as low as 0.1 and 1.5 ppb, respectively. Furthermore, Cu and Zn ions were successfully detected in biofluids, that is, urine and sweat, in a wide range of concentration (urine Cu: 10-500 ppb; urine Zn: 200-600 ppb; sweat Cu: 300-1500 ppb; and sweat Zn: 500-1500 ppb). The fabricated flexible sensor also possesses other advantages of ultra-repeatability and excellent stability. Thus, these advantages provide a great possibility for the noninvasive smart monitoring of heavy metals in the future.

An Electrodeposited MXene-Ti3C2Tx Nanosheets Functionalized by Task-Specific Ionic Liquid for Simultaneous and Multiplexed Detection of Bladder Cancer Biomarkers.

Controlled deposition of 2D multilayered nanomaterials onto different electrodes to design a highly sensitive biosensing platform utilizing their active inherent electrochemistry is extremely challenging. Herein, a green, facile, and cost-effective one-pot deposition mechanism of 2D MXene-Ti3C2Tx nanosheets (MXNSs) onto conductive electrodes within few minutes via electroplating (termed electroMXenition) is reported for the first time. The redox reaction in the colloidal MXNS solution under the effect of a constant applied potential generates an electric field, which drives the nanoparticles toward a specific electrode interface such that they are cathodically electroplated. A task-specific ionic liquid, that is, 4-amino-1-(4-formyl-benzyl) pyridinium bromide (AFBPB), is exploited as a multiplex host arena for the substantial immobilization of MXNSs and covalent binding of antibodies. A miniaturized, single-masked gold dual interdigitated microelectrode (DIDµE) is microfabricated and presented by investigating the benefit of AFBPB coated on MXNSs. The resulting MXNSs-AFBPB-film-modified DIDµE biosensor exhibited a 7× higher redox current than bare electrodes owing to the uniform deposition. Using Apo-A1 and NMP 22 as model bladder cancer analytes, this newly developed dual immunosensor demonstrated precise and large linear ranges over five orders of significance with limit of detection values as low as 0.3 and 0.7 pg mL-1, respectively.

Highly flexible and conductive poly (3, 4-ethylene dioxythiophene)-poly (styrene sulfonate) anchored 3-dimensional porous graphene network-based electrochemical biosensor for glucose and pH detection in human perspiration.

The patterned LIG flakes are generally not interconnected due to the line gap of the laser ray, leading to lower uniform conductivity and fragile graphene. Thus, the fabrication of a highly conductive and mechanically robust LIG-based biosensing platform remains challenging. In this study, the fabrication of a flexible electrochemical biosensor is reported based on poly (3, 4-ethylene dioxythiophene)-poly (styrene sulfonate) (PEDOT:PSS) modified 3-dimensional (3D) stable porous laser-induced graphene (LIG) for the detection of glucose and pH. PEDOT:PSS was spray-coated on the LIG to improve electrode robustness and deliver uniform electrical conductivity. The as-prepared PEDOT:PSS modified LIG (PP/LIG) was characterized using field-emission scanning electron microscopy (FESEM), x-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and Fourier-transform infrared spectroscopy (FTIR). Platinum and palladium nanoparticles (Pt@Pd) were successfully electrodeposited on PP/LIG, markedly enhancing the electrocatalytic activity for glucose detection. The fabricated biosensor exhibited an excellent amperometric response to glucose with a wide linear range of 10 µM - 9.2 mM, a high sensitivity of 247.3 µAmM-1cm-2, and a low detection limit (LOD) of 3 µM, with high selectivity. In addition, the pH sensor was functionalized by the polyaniline (PANI) on PP/LIG, and it also exhibited excellent potentiometric response with a high sensitivity of 75.06 mV/pH in the linear range of pH 4 - 7. Ultimately, the feasibility of the biosensor was confirmed by the analysis of human perspiration collected during physical exercise. This approach validates the utility of the novel fabrication procedure, and the potential of the LIG-conductive polymer composite for biosensing applications.

Wearable Capacitive Pressure Sensor Based on MXene Composite Nanofibrous Scaffolds for Reliable Human Physiological Signal Acquisition.

In recent years, highly sensitive pressure sensors that are flexible, biocompatible, and stretchable have attracted significant research attention in the fields of wearable electronics and smart skin. However, there has been a considerable challenge to simultaneously achieve highly sensitive, low-cost sensors coupled with optimum mechanical stability and an ultralow detection limit for subtle physiological signal monitoring devices. Targeting aforementioned issues, herein, we report the facile fabrication of a highly sensitive and reliable capacitive pressure sensor for ultralow-pressure measurement by sandwiching MXene (Ti3C2Tx)/poly(vinylidene fluoride-trifluoroethylene) (PVDF-TrFE) composite nanofibrous scaffolds as a dielectric layer between biocompatible poly-(3,4-ethylenedioxythiophene) polystyrene sulfonate /polydimethylsiloxane electrodes. The fabricated sensor exhibits a high sensitivity of 0.51 kPa-1 and a minimum detection limit of 1.5 Pa. In addition, it also enables linear sensing over a broad pressure range (0-400 kPa) and high reliability over 10,000 cycles even at extremely high pressure (>167 kPa). The sensitivity of the nanofiber-based sensor is enhanced by MXene loading, thereby increasing the dielectric constant up to 40 and reducing the compression modulus to 58% compared with pristine PVDF-TrFE nanofiber scaffolds. The proposed sensor can be used to determine the health condition of patients by monitoring physiological signals (pulse rate, respiration, muscle movements, and eye twitching) and also represents a good candidate for a next generation human-machine interfacing device.