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In this work, a highly stable Ca2+ ion-selective sensor was successfully developed by depositing a poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonate) (PEDOT:PSS) layer on top of a carbon paste electrode as an ion-electron transducing layer. The PEDOT:PSS was treated by a co-solvent of ethylene glycol (EG) using the bath-sonication technique to enhance electrical and electrochemical characteristics, and finally coated with Ca2+ ion-selective membrane cocktail. The developed Ca2+ ion-selective electrode (Ca2+-ISE) showed excellent electrochemical properties by much-improved charge transfer kinetics with remarkable electric conductivity. The fabricated Ca2+-ISE exhibited an excellent sensitivity of 37.7 mV/decade (n = 4) in the range from 10-4 to 10-1 M with a rapid response (< 20 seconds). Moreover, the EG-treated PEDOT:PSS (PEDOT:PSS-EG) based ISE showed negligible responses for primary interfering ions of human biofluid samples, proving significant potential selectivity. Furthermore, the negligible drift of open circuit potential (2.78 μV/s) proved the stability of the PEDOT:PSS-EG compared to pristine PEDOT:PSS(10.63 μV/s) based ISE. Based on these analyses, it can be expected that the organic solvent treatment on PEDOT:PSS will pave the way for long-term monitoring of other biochemical compounds.

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.

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

In this work, we prepared hollow gold nanospheres (HAuNS) with rough surfaces and strong light absorption in the NIR region. Based on as-made HAuNS materials, photothermal sterilization patches using filter paper was prepared. When 808 nm and 4 W/cm2 laser light was irradiated on the patch containing 50 ppm of HAuNS, the temperature of patch surface increased to 63 °C. The photothermal conversion efficiency of the patch was found to be 38.8% and is enhanced by the overlap between the heat emission of nearby particles in the patch. The prepared patch was placed into an Escherichia coli culture medium with irradiation of NIR (pulsed laser by manually on/off). E. coli in direct contact with patch could be killed by local heating on the patch surface. Approximately 99% of the bacteria was killed compared to control test. Therefore, this patch can be applied to wounds to block the entry of bacteria from the outside for the prevention of secondary infections and the acceleration of treatment with the photothermal effect caused by NIR irradiation.

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 Ti

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

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) nanoc...

In this study, highly flexible and conductive dry electrodes were developed using a biocompatible polymer (poly (ethylene dioxythiophene): poly (styrene sulfonate), (PEDOT:PSS)) loaded mechanically robust laser-induced graphene (LIG). The circular-shaped LIG electrode with an area of 0.7854 cm2 was directly patterned using a CO2 laser. The PEDOT:PSS was spray-coated on the LIG to enhance the electrical conductivity (164.2 Scm−1) and electrode robustness. The prepared electrodes were characterized by the Field Emission Scanning Electron Microscope (FESEM), X-ray photoelectron spectroscopy (XPS), X-Ray Diffraction (XRD) and Raman Spectra. Experimental results showed that the surface resistivity and skin contact impedance of the electrode were 17.4 Ω/sq and 385 kΩ at 10 Hz. The impedance at the electrode–skin interface was relatively stable, thereby the SNR value of the electrocardiogram (ECG) signal obtained from the fabricated electrodes (12.9 dB) was comparable to Ag/AgCl electrodes (13.3 dB). The electrodes could be effectively and symmetrically attached to the skin since it is thin and flexible. The fabricated electrodes were successfully operated when the participant is resting, and fewer motion artifacts are observed during movement. Finally, ECG signals were demonstrated in a mobile application for real-time and long-term monitoring by attaching participants’ fingers with optimized dry electrodes.

We fabricated high-performance paper-based epidermal sensors on biocompatible nylon-membrane without utilizing any harmful chemicals & complicated processes. The proposed epidermal sensor was fabricated using thermally reduced graphene oxide and a nylon-membrane (TRGO/NM). The epidermal sensor (TRGO/NM) has been developed to reduce the usage of Ag/AgCl (sticky sensor). The sensor demonstrates high sensitivity (sheet resistance = 40 Ω/sq.), because skin-contact impedance was ∼20KΩ at low frequency. We found that the TRGO/NM sensor developed micro-gaps on the surface of NM, which generated resistance changes under tensile and compressive strain. The TRGO/NM sensor shows fast response time (∼0.5 s), relaxation time (∼0.5 s), and a highly stable with an excellent bending-stretching response. We applied the epidermal sensor for obtaining electrocardiography (ECG), electroencephalography (EEG), and electromyography (EMG) as well as monitoring human motions also. The biocompatibility of the TRGO/NM sensor was confirmed by performing the cytotoxicity test.

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 Ti

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

It is highly demanded to develop flexible strain sensors with high sensitivity, a wide working range, and excellent reliability. We newly applied 3,4-ethylene dioxythiophene (EDOT) in-situ polymerization self-assembly on MXene-Ti 3 C 2 T x flakes in an aqueous solution in order to simultaneously improve both the sensitivity and working range of the strain sensor patch. MXene-Ti 3 C 2 T x @EDOT was uniformly deposited on the laser-induced graphene (LIG) embedded styrene ethylene butylene styrene (SEBS) stretchable substrate by electrophoretic deposition without any oxidants. The as-fabricated sensor can detect minute to large deformations with high GF up to 2075, large strain range (>28%), and excellent reliability (>20000 cycles). A flexible battery-free near field communication (NFC) wireless system was developed and transmit measurements to a smartphone.