Bio-Inspired Sensory Receptors for Artificial-Intelligence Perception.

In the era of artificial intelligence (AI), there is a growing interest in replicating human sensory perception. Selective and sensitive bio-inspired sensory receptors with synaptic plasticity have recently gained significant attention in developing energy-efficient AI perception. Various bio-inspired sensory receptors and their applications in AI perception are reviewed here. The critical challenges for the future development of bio-inspired sensory receptors are outlined, emphasizing the need for innovative solutions to overcome hurdles in sensor design, integration, and scalability. AI perception can revolutionize various fields, including human-machine interaction, autonomous systems, medical diagnostics, environmental monitoring, industrial optimization, and assistive technologies. As advancements in bio-inspired sensing continue to accelerate, the promise of creating more intelligent and adaptive AI systems becomes increasingly attainable, marking a significant step forward in the evolution of human-like sensory perception.

Utilizing a High-Performance Piezoelectric Nanocomposite as a Self-Activating Component in Piezotronic Artificial Mechanoreceptors.

Challenges such as poor dispersion and insufficient polarization of BaTiO3 (BTO) nanoparticles (NPs) within poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) composites have hindered their piezoelectricity, limiting their uses in pressure sensors, nanogenerators, and artificial sensory synapses. Here, we introduce a high-performance piezoelectric nanocomposite material consisting of P(VDF-TrFE)/modified-BTO (mBTO) NPs for use as a self-activating component in a piezotronic artificial mechanoreceptor. To generate high-performance piezoelectric nanocomposite materials, the surface of BTO is hydroxylated, followed by the covalent attachment of (3-aminopropyl)triethoxysilane to improve the dispersibility of mBTO NPs within the P(VDF-TrFE) matrix. We also aim to enhance the crystallization degree of P(VDF-TrFE), the efficiency characteristics of mBTO, and the poling efficiency, even when incorporating small amounts of mBTO NPs. The piezoelectric potential mechanically induced from the P(VDF-TrFE)/mBTO NPs nanocomposite was three times greater than that from P(VDF-TrFE) and twice as high as that from the P(VDF-TrFE)/BTO NPs nanocomposite. The piezoelectric potential generated by mechanical stimuli on the piezoelectric nanocomposite was utilized to activate the synaptic ionogel-gated field-effect transistor for the development of self-powered piezotronics artificial mechanoreceptors on a polyimide substrate. The device successfully emulated fast-adapting (FA) functions found in biological FA mechanoreceptors. This approach has great potential for applications to future intelligent tactile perception technology.

Metal-enhanced fluorescence biosensor integrated in capillary flow-driven microfluidic cartridge for highly sensitive immunoassays.

Point-of-care testing (POCT) for low-concentration protein biomarkers remains challenging due to limitations in biosensor sensitivity and platform integration. This study addresses this gap by presenting a novel approach that integrates a metal-enhanced fluorescence (MEF) biosensor within a capillary flow-driven microfluidic cartridge (CFMC) for the ultrasensitive detection of the Parkinson's disease biomarker, aminoacyl-tRNA synthetase complex interacting multi-functional protein 2 (AIMP-2). Crucial point to this approach is the orientation-controlled immobilization of capture antibody on a nanodimple-structured MEF substrate within the CFMC. This strategy significantly enhances fluorescence signals without quenching, enabling accurate quantification of low-concentration AIMP-2 using a simple digital fluorescence microscope with a light-emitting diode excitation source and a digital camera. The resulting platform exhibits exceptional sensitivity, achieving a limit of detection in the pg/mL range for AIMP-2 in human serum. Additionally, the CFMC design incorporates a capillary-driven passive sample transport mechanism, eliminating the need for external pumps and further simplifying the detection process. Overall, this work demonstrates the successful integration of MEF biosensing with capillary microfluidics for point-of-care applications.

Levofloxacin+Tetracycline Quadruple Regimen for Eradication of Helicobacter pylori: A Multicenter Multinational Randomized Controlled Trial.

Background: The ideal combination regimen for Helicobacter pylori (HP) eradication has not yet been determined and the success rate of HP eradication has been extensively reduced worldwide due to increasing antibiotic resistance. So this multinational multi-center randomized controlled trial was designed to evaluate the efficacy of tetracycline +levofloxacin for HP eradication. Methods: During a 6-month period, all of the cases with HP infection in eight referral tertiary centers of three countries were included and randomly allocated to receive either tetracycline + levofloxacin or clarithromycin plus amoxicillin quadruple regimen for two weeks. For all of the participants, pantoprazole was continued for 4 more weeks and after one to two weeks of off-therapy, they underwent urea breath test C13 to prove eradication. Results: Overall 788 patients were included (358 male (45.4%), average age 44.2 years). They were diagnosed as having non-ulcer dyspepsia (516 cases, 65.5%), peptic ulcer disease (PUD) (234 cases, 29.69%), and intestinal metaplasia (38 cases, 4.8%). Racially 63.1% were Caucasian, 14.5% Arab, 15.6% African, and 6.1% Asian. The participants were randomly allocated to groups A and B to receive either tetracycline + levofloxacin or clarithromycin. Among groups A and B in intention to treat (ITT) and per protocol (PP) analysis, 75.2% & 82.1% (285 cases) and 67.5% & 70.1% (276 cases) of participants achieved eradication, respectively (P = 0.0001). The complete compliance rate in groups A and B were 84.4% and 83.6%, respectively. During the study, 33.5% of the participants in group A (127 cases) reported side effects while the complication rate among group B was 27.9% (114 cases, P = 0.041). The most common complaints among groups A and B were nausea and vomiting (12.6% & 9.3%) and abdominal pain (4.48% & 2.68%), respectively. The rate of severe complications that caused discontinuation of medication in groups A and B were 2.1% and 1.46%, respectively (P = 679). In subgroup analysis, the eradication rates of tetracycline+levofloxacin among patients with non-ulcer dyspepsia, PUD, and intestinal metaplasia were 79.4%, 88.1%, and 73.9%, respectively. These figures in group B (clarithromycin base) were 71.3%, 67.6%, and 61.5% respectively (P = 0.0001, 0.0001, and 0.043). Conclusion: Overall, the combination of tetracycline+levofloxacin is more efficient for HP eradication in comparison with clarithromycin+amoxicillin despite more complication rate. In areas with a high rate of resistance to clarithromycin, this therapeutic regimen could be an ideal choice for HP eradication, especially among those who were diagnosed with PUD.

A stretchable ultraviolet-to-NIR broad spectral photodetector using organic-inorganic vertical multiheterojunctions.

Stretchable broadband photodetectors (PDs) are attractive for applications in wearable optoelectronics and personal healthcare. However, the development of stretchable broadband PDs is limited by difficulties in obtaining materials, designing device structures, and finding reliable fabrication processes. Here, we report stretchable broadband PDs by forming organic-inorganic vertical multiheterojunctions on a three-dimensionally micro-patterned stretchable substrate (3D-MPSS). The stress-adaptable 3D-MPSS structure allows all layers of the PD coated on it to sustain tensile strains. Generation of photovoltage in the vertical hybrid structure of PbS quantum dots/ZnO nanorods as a photo-responsive material on poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) as a transport channel is considred to be the mechanism of the device response to UV-Vis-NIR. The fabricated PDs present responsivity to UV (365 nm), Vis (565 nm and 660 nm), and NIR (880 nm and 970 nm) light, as well as reliable electrical performance under applied stretching up to 30%.

A flexible artificial intrinsic-synaptic tactile sensory organ.

Imbuing bio-inspired sensory devices with intelligent functions of human sensory organs has been limited by challenges in emulating the preprocessing abilities of sensory organs such as reception, filtering, adaptation, and sensory memory at the device level itself. Merkel cells, which is a part of tactile sensory organs, form synapse-like connections with afferent neuron terminals referred to as Merkel cell-neurite complexes. Here, inspired by structure and intelligent functions of Merkel cell-neurite complexes, we report a flexible, artificial, intrinsic-synaptic tactile sensory organ that mimics synapse-like connections using an organic synaptic transistor with ferroelectric nanocomposite gate dielectric of barium titanate nanoparticles and poly(vinylidene fluoride-trifluoroethylene). Modulation of the post-synaptic current of the device induced by ferroelectric dipole switching due to triboelectric-capacitive coupling under finger touch allowed reception and slow adaptation. Modulation of synaptic weight by varying the nanocomposite composition of gate dielectric layer enabled tuning of filtering and sensory memory functions.

A wearable lab-on-a-patch platform with stretchable nanostructured biosensor for non-invasive immunodetection of biomarker in sweat.

Conformable, wearable biosensor-integrated systems are a promising approach to non-invasive and quantitative on-body detection of biomarkers in body fluids. However, realizing such a system has been slowed by the difficulty of fabricating a soft affinity-based biosensor patch capable of precise on-body fluid handling with minimal wearer intervention and a simple measurement protocol. Herein, we demonstrate a conformable, wearable lab-on-a-patch (LOP) platform composed of a stretchable, label-free, impedimetric biosensor and a stretchable microfluidic device for on-body detection of the hormone biomarker, cortisol. The all-in-one, stretchable microfluidic device can precisely collect and deliver sweat for cortisol quantitation and offers one-touch operation of reagent delivery for simultaneous electrochemical signal generation and washing. Three-dimensional nanostructuring of the Au working electrode enables the high sensitivity required to detect the pM-levels of cortisol in sweat. Our integrated LOP detected sweat cortisol quantitatively and accurately during exercise. This LOP will open a new horizon for non-invasive, highly sensitive, and quantitative on-body immunodetection for wearable personal diagnostics.

Recent progress, challenges, and prospects of fully integrated mobile and wearable point-of-care testing systems for self-testing.

The rapid growth of research in the areas of chemical and biochemical sensors, lab-on-a-chip, mobile technology, and wearable electronics offers an unprecedented opportunity in the development of mobile and wearable point-of-care testing (POCT) systems for self-testing. Successful implementation of such POCT technologies leads to minimal user intervention during operation to reduce user errors; user-friendly, easy-to-use and simple detection platforms; high diagnostic sensitivity and specificity; immediate clinical assessment; and low manufacturing and consumables costs. In this review, we discuss recent developments in the field of highly integrated mobile and wearable POCT systems. In particular, aspects of sample handling platforms, recognition elements and sensing methods, and new materials for signal transducers and powering devices for integration into mobile or wearable POCT systems will be highlighted. We also summarize current challenges and future prospects for providing personal healthcare with sample-in result-out mobile and wearable POCT.

Stretchable and transparent nanofiber-networked electrodes based on nanocomposites of polyurethane/reduced graphene oxide/silver nanoparticles with high dispersion and fused junctions.

Creating stretchable and transparent conductive electrodes for stretchable and transparent electronics is very challenging due to difficulties in obtaining adequate optical and mechanical properties simultaneously. Here, we designed a stretchable and transparent nanofiber-networked electrode (STNNE) based on a networked structure of electrospun stretchable nanofibers made from a mixture of polyurethane (PU)/reduced graphene oxide (rGO)/silver nanoparticles (AgNPs). The STNNE showed a sheet resistance as small as 210 Ω sq-1 at an optical transparency of ∼83%. In addition, the STNNE has up to 40% mechanical stretchability and relatively high electrical stability (i.e., a resistance change of 83% at 40% stretching). The good electrical conductance, mechanical stretchability, and electrical stability under static/dynamic stretching or after cyclic stretching are attributed to the high dispersion of AgNPs in the nanofibers, which creates more electrically conductive pathways and forms fused junctions at the intersections between nanofibers during electrospinning. As a demonstration, an STNNE with a simple selective-patterning process was employed to fabricate a stretchable capacitive touch sensor with a stretchable and transparent dielectric (PU) on a polydimethylsiloxane substrate. The signal output of the touch sensor upon touching under stretched conditions was nearly unchanged. This STNNE has great potential in stretchable and transparent electronics.

Highly Electrocatalytic, Durable, and Stretchable Nanohybrid Fiber for On-Body Sweat Glucose Detection.

A conformal patch biosensor that can detect biomolecules is one promising technology for wearable sweat glucose self-monitoring. However, developing such a patch is challenging because conferring stretchability to its components is difficult. Herein, we demonstrate a platform for a nonenzymatic, electrochemical sensor patch: a wrinkled, stretchable, nanohybrid fiber (WSNF) in which Au nanowrinkles partially cover the reduced graphene oxide (rGO)/polyurethane composite fiber. The WSNF has high electrocatalytic activity because of synergetic effects between the Au nanowrinkles and the oxygen-containing functional groups on the rGO-supporting matrix which promote the dehydrogenation step in glucose oxidation. The WSNF offers stretchability, high sensitivity, low detection limit, high selectivity against interferents, and high ambient-condition stability, and it can detect glucose in neutral conditions. If this WSNF sensor patch were sewn onto a stretchable fabric and attached to the human body, it could continuously measure glucose levels in sweat to accurately reflect blood glucose levels.

A Stretchable Strain-Insensitive Temperature Sensor Based on Free-Standing Elastomeric Composite Fibers for On-Body Monitoring of Skin Temperature.

To realize the potential applications of stretchable sensors in the field of wearable health monitoring, it is essential to develop a stable sensing device with robust electrical and mechanical properties in the present of varying external conditions. Herein, we demonstrate a stretchable temperature sensor with the elimination of strain-induced interference via geometric engineering of the free-standing stretchable fibers (FSSFs) of reduced graphene oxide/polyurethane composite. The FSSFs were formed in serpentine structures and enabled the implementation of a strain-insensitive stretchable temperature sensor. On the basis of the controlled reduction time of graphene oxide, we can modulate the response and thermal index of the device. These results are attributed to the variation in the density of oxygen-containing functional groups in the FSSFs, which affect the hopping charge transport and thermal generation of excess carriers. The FSSF temperature sensor yields increased responsivity (0.8%/°C), stretchability (90%), sensing resolution (0.1 °C), and stability in response to applied stretching (±0.37 °C for strains ranging from 0 to 50%). When the sensor is sewn onto a stretchable bandage and attached to the human body, it can detect the temperature changes of the human skin during different body motions in a continuous and stable manner.

Stretchable, Transparent, Tough, Ultrathin, and Self-limiting Skin-like Substrate for Stretchable Electronics.

Human skin is highly stretchable at low strain but becomes self-limiting when deformed at large strain due to stiffening caused by alignment of a network of stiff collagen nanofibers inside the tissue beneath the epidermis. To imitate this mechanical behavior and the sensory function of human skin, we fabricated a skin-like substrate with highly stretchable, transparent, tough, ultrathin, mechanosensory, and self-limiting properties by incorporating piezoelectric crystalline poly((vinylidene fluoride)- co-trifluoroethylene) (P(VDF-TrFE)) nanofibers with a high modulus into the low modulus matrix of elastomeric poly(dimethylsiloxane). Randomly distributed P(VDF-TrFE) nanofibers in the elastomer matrix conferred a self-limiting property to the skin-like substrate so that it can easily stretch at low strain but swiftly counteract rupturing in response to stretching. The stretchability, toughness, and Young's modulus of the ultrathin (∼62 µm) skin-like substrate with high optical transparency could be tuned by controlling the loading of nanofibers. Moreover, the ultrathin skin-like substrate with a stretchable temperature sensor fabricated on it demonstrated the ability to accommodate bodily motion-induced strain in the sensor while maintaining its mechanosensory and thermosensory functionalities.

Freestanding, Fiber-Based, Wearable Temperature Sensor with Tunable Thermal Index for Healthcare Monitoring.

Fiber-based sensors integrated on textiles or clothing systems are required for the next generation of wearable electronic platforms. Fiber-based physical sensors are developed, but the development of fiber-based temperature sensors is still limited. Herein, a new approach to develop wearable temperature sensors that use freestanding single reduction graphene oxide (rGO) fiber is proposed. A freestanding and wearable temperature-responsive rGO fiber with tunable thermal index is obtained using simple wet spinning and a controlled graphene oxide reduction time. The freestanding fiber-based temperature sensor shows high responsivity, fast response time (7 s), and good recovery time (20 s) to temperature. It also maintains its response under an applied mechanical deformation. The fiber device fabricated by means of a simple process is easily integrated into fabric such as socks or undershirts and can be worn by a person to monitor the temperature of the environment and skin temperature without interference during movement and various activities. These results demonstrate that the freestanding fiber-based temperature sensor has great potential for fiber-based wearable electronic platforms. It is also promising for applications in healthcare and biomedical monitoring.

An Omnidirectionally Stretchable Photodetector Based on Organic-Inorganic Heterojunctions.

Omnidirectionally stretchable photodetectors are limited by difficulties in designing material and fabrication processes that enable stretchability in multiaxial directions. Here, we propose a new approach involving an organic-inorganic p-n heterojunction photodetector comprised of free-standing ZnO nanorods grown on a poly(3,4-ethylenedioxythiophene)-polystyrene sulfonate transport layer coated on a three-dimensional micropatterned stretchable substrate containing bumps and valleys. This structure allows for efficient absorption of stretching strain. This approach allows the device to accommodate large tensile strain in all of the directions. The device behaves as a photogated p-n heterojunction photodetector in which current modulation was obtained by sensing the mechanisms that rely on photovoltage and photogating effects. The device exhibits a high photoresponse to UV light and reliable electrical performance under applied stretching in uniaxial and omniaxial directions. Furthermore, the device can be easily and conformally attached to a human wrist. This allowed us to investigate the response of the device to UV light during human activity.

Stretchable, Transparent, and Stretch-Unresponsive Capacitive Touch Sensor Array with Selectively Patterned Silver Nanowires/Reduced Graphene Oxide Electrodes.

Stretchable and transparent touch sensors are essential input devices for future stretchable transparent electronics. Capacitive touch sensors with a simple structure of only two electrodes and one dielectric are an established technology in current rigid electronics. However, the development of stretchable and transparent capacitive touch sensors has been limited due to changes in capacitance resulting from dimensional changes in elastomeric dielectrics and difficulty in obtaining stretchable transparent electrodes that are stable under large strains. Herein, a stretch-unresponsive stretchable and transparent capacitive touch sensor array was demonstrated by employing stretchable and transparent electrodes with a simple selective-patterning process and by carefully selecting dielectric and substrate materials with low strain responsivity. A selective-patterning process was used to embed a stretchable and transparent silver nanowires/reduced graphene oxide (AgNWs/rGO) electrode line into a polyurethane (PU) dielectric layer on a polydimethylsiloxane (PDMS) substrate using oxygen plasma treatment. This method provides the ability to directly fabricate thin film electrode lines on elastomeric substrates and can be used in conventional processes employed in stretchable electronics. We used a dielectric (PU) with a Poisson's ratio smaller than that of the substrate (PDMS), which prevented changes in the capacitance resulting from stretching of the sensor. The stretch-unresponsive touch sensing capability of our transparent and stretchable capacitive touch sensor has great potential in wearable electronics and human-machine interfaces.

Recent Progress on Stretchable Electronic Devices with Intrinsically Stretchable Components.

Stretchable electronic devices with intrinsically stretchable components have significant inherent advantages, including simple fabrication processes, a high integrity of the stacked layers, and low cost in comparison with stretchable electronic devices based on non-stretchable components. The research in this field has focused on developing new intrinsically stretchable components for conductors, semiconductors, and insulators. New methodologies and fabrication processes have been developed to fabricate stretchable devices with intrinsically stretchable components. The latest successful examples of stretchable conductors for applications in interconnections, electrodes, and piezoresistive devices are reviewed here. Stretchable conductors can be used for electrode or sensor applications depending on the electrical properties of the stretchable conductors under mechanical strain. A detailed overview of the recent progress in stretchable semiconductors, stretchable insulators, and other novel stretchable materials is also given, along with a discussion of the associated technological innovations and challenges. Stretchable electronic devices with intrinsically stretchable components such as field-effect transistors (FETs), photodetectors, light-emitting diodes (LEDs), electronic skins, and energy harvesters are also described and a new strategy for development of stretchable electronic devices is discussed. Conclusions and future prospects for the development of stretchable electronic devices with intrinsically stretchable components are discussed.

Flexible and Stretchable Physical Sensor Integrated Platforms for Wearable Human-Activity Monitoringand Personal Healthcare.

Flexible and stretchable physical sensors that can measure and quantify electrical signals generated by human activities are attracting a great deal of attention as they have unique characteristics, such as ultrathinness, low modulus, light weight, high flexibility, and stretchability. These flexible and stretchable physical sensors conformally attached on the surface of organs or skin can provide a new opportunity for human-activity monitoring and personal healthcare. Consequently, in recent years there has been considerable research effort devoted to the development of flexible and stretchable physical sensors to fulfill the requirements of future technology, and much progress has been achieved. Here, the most recent developments of flexible and stretchable physical sensors are described, including temperature, pressure, and strain sensors, and flexible and stretchable sensor-integrated platforms. The latest successful examples of flexible and stretchable physical sensors for the detection of temperature, pressure, and strain, as well as their novel structures, technological innovations, and challenges, are reviewed first. In the next section, recent progress regarding sensor-integrated wearable platforms is overviewed in detail. Some of the latest achievements regarding self-powered sensor-integrated wearable platform technologies are also reviewed. Further research direction and challenges are also proposed to develop a fully sensor-integrated wearable platform for monitoring human activity and personal healthcare in the near future.

An All-Elastomeric Transparent and Stretchable Temperature Sensor for Body-Attachable Wearable Electronics.

A transparent stretchable (TS) gated sensor array with high optical transparency, conformality, and high stretchability of up to 70% is demonstrated. The TS-gated sensor array has high responsivity to temperature changes in objects and human skin. This unprecedented TS-gated sensor array, as well as the integrated platform of the TS-gated sensor with a transparent and stretchable strain sensor, show great potential for application to wearable skin electronics for recognition of human activity.

Transparent Stretchable Self-Powered Patchable Sensor Platform with Ultrasensitive Recognition of Human Activities.

Monitoring of human activities can provide clinically relevant information pertaining to disease diagnostics, preventive medicine, care for patients with chronic diseases, rehabilitation, and prosthetics. The recognition of strains on human skin, induced by subtle movements of muscles in the internal organs, such as the esophagus and trachea, and the motion of joints, was demonstrated using a self-powered patchable strain sensor platform, composed on multifunctional nanocomposites of low-density silver nanowires with a conductive elastomer of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/polyurethane, with high sensitivity, stretchability, and optical transparency. The ultra-low-power consumption of the sensor, integrated with both a supercapacitor and a triboelectric nanogenerator into a single transparent stretchable platform based on the same nanocomposites, results in a self-powered monitoring system for skin strain. The capability of the sensor to recognize a wide range of strain on skin has the potential for use in new areas of invisible stretchable electronics for human monitoring. A new type of transparent, stretchable, and ultrasensitive strain sensor based on a AgNW/PEDOT:PSS/PU nanocomposite was developed. The concept of a self-powered patchable sensor system integrated with a supercapacitor and a triboelectric nanogenerator that can be used universally as an autonomous invisible sensor system was used to detect the wide range of strain on human skin.