Flexible sensor

Bio-inspired transistor synapses use solid electrolytes to achieve low-power operation and rich synaptic behaviors via ion diffusion and trapping. While these neuromorphic devices hold great promise, they still suffer from challenges such as high leakage currents and power consumption, electrolysis risk, and irreversible conductance changes due to long-range ion migrations and permanent ion trapping. In addition, their response to light is generally limited because of "exciton-polaron quenching", which restricts their potential in in-sensor neuromorphic visions...

Anisotropic strain sensors capable of multidirectional sensing are crucial for advanced sensor applications in human motion detection. However, current anisotropic sensors encounter challenges in achieving a balance among high sensitivity, substantial stretchability, and a wide linear detection range. To address these challenges, a facile freeze-casting strategy was employed to construct oriented filler networks composed of carbon nanotubes and conductive carbon black within a brominated butyl rubber ionomer (iBIIR) matrix...

Previous works have focused on enhancing the tensile properties, mechanical flexibility, biocompatibility, and biodegradability of wearable devices for real-time and continuous health management. Silk proteins, including silk fibroin (SF) and sericin, show great advantages in wearable devices due to their natural biodegradability, excellent biocompatibility, and low fabrication cost. Moreover, these silk proteins possess great potential for functionalization and are being explored as promising candidates for multifunctional wearable devices with sensory capabilities and therapeutic purposes...

Facile fabrication of highly conductive and self-encapsulated graphene electronics is in urgent demand for carbon-based integrated circuits, field effect transistors, optoelectronic devices, and flexible sensors. The current fabrication of these electronic devices is mainly based on layer-by-layer techniques (separate circuit preparation and encapsulation procedures), which show multistep fabrication procedures, complicated renovation/repair procedures, and poor electrical property due to graphene oxidation and exfoliation...

CALF-20 was recently identified as a benchmark sorbent for CO2 capture at the industrial scale, however comprehensive atomistic insight into its mechanical/thermal properties under working conditions is still lacking. In this study, we developed a general-purpose machine-learned potential (MLP) for the CALF-20 MOF framework that predicts the thermodynamic and mechanical properties of the structure at finite temperatures within first-principles accuracy. Interestingly, CALF-20 was demonstrated to exhibit both negative area compression and negative thermal expansion...

A novel double-network conductive hydrogel based on lithium acetate/gelatin/polyacrylamide (PAAM) was synthesized by heating-cooling and subsequent γ-ray radiation-induced polymerization and cross-linking. Owing to the hydrogen bonding interaction between lithium acetate, physical cross-linked gelatin, and chemical cross-linked PAAM, the resultant hydrogel exhibited high tensile strength (1260 kPa), high ionic conductivity (35.2 mS cm-1 ), notch-insensitivity (tensile strength 415 kPa, elongation at break 872% with transverse notch), and extensive strain monitoring range (0...

MXene-inspired two-dimensional (2D) materials like Ti3 C2 T x are widely known for their versatile properties, including surface plasmon, higher electrical conductivity, exceptional in-plane tensile strength, EMI shielding, and IR thermal properties. The MXene nanosheets coupled poly(vinylidene fluoride) (PVDF) nanofibers with d 33 ∼-26 pm V-1 are able to capture the smaller thermal fluctuation due to a superior pyroelectric coefficient of ∼130 nC m-2 K-1 with an improved (∼7 times with respect to neat PVDF nanofibers) pyroelectric current figure of merit (FOMi )...

Arid zone grassland is a crucial component of terrestrial ecosystems and plays a significant role in ecosystem protection and soil erosion prevention. However, accurately mapping grassland spatial information in arid zones presents a great challenge. The accuracy of remote sensing grassland mapping in arid zones is affected by spectral variability caused by the highly diverse landscapes. In this study, we explored the potential of a rectangular tile classification model, constructed using the random forest algorithm and integrated images from Sentinel-1A (synthetic aperture radar imagery) and Sentinel-2 (optical imagery), to enhance the accuracy of grassland mapping in the semiarid to arid regions of Ordos, China...

As tactile force sensing has become increasingly significant in the field of machine haptics, achieving multidimensional force sensing remains a challenge. We propose a 3D flexible force sensor that consists of an axisymmetric hemispherical protrusion and four equally sized quarter-circle electrodes. By simulating the device using a force and electrical field model, it has been found that the magnitude and direction of the force can be expressed through the voltage relationship of the four electrodes when the magnitude of the shear force remains constant and its direction varies within 0-360°...

Bio-semiconductors are expected to be similar to organic semiconductors; however, they have not been utilized in application yet. In this study, we show the origin of electron appearance, N- and S-type negative resistances, rectification, and switching effects of semiconductors with energy storage capacities of up to 418.5 mJ/m2 using granulated amorphous kenaf cellulose particles (AKCPs). The radical electrons in AKCP at 295 K appear in cellulose via the glycosidic bond C1 -O1 · -C4 . Hall effect measurements indicate an n-type semiconductor with a carrier concentration of 9...

The fundamentals, performance, and applications of piezoresistive strain sensors based on polymer nanocomposites are summarized herein. The addition of conductive nanoparticles to a flexible polymer matrix has emerged as a possible alternative to conventional strain gauges, which have limitations in detecting small strain levels and adapting to different surfaces. The evaluation of the properties or performance parameters of strain sensors such as the elongation at break, sensitivity, linearity, hysteresis, transient response, stability, and durability are explained in this review...

In order to reduce the damage to people's health from diseases that attack the respiratory system such as COVID-19, asthma, and pneumonia, it is desired that patients' breathing can be monitored and alerted in real-time. The emergence of wearable health detection sensing devices has provided a relatively good response to this problem. However, there are still problems such as complex structure and poor performance. This paper introduces a laser-induced graphene (LIG) device that is attached to PDMS. The LIG is produced by laser irradiation of Nomex and subsequently transferred and attached to the PDMS...

Hybrid ferroelastic crystals have emerged as a hot research topic in recent years owing to their prospective applications in piezoelectric sensors, mechanical switches, and optoelectronic devices. Nevertheless, most of the documented materials exhibit one-step or two-step ferroelastic phase transition(s), and those with multistep ferroelastic transitions are extremely scarce. We present a new hexagonal molecular perovskite based on a fluoro-substituted flexible cyclic ammonium cation, (1-fluoromethyl-1-methylpyrrolidine)[CdCl3 ] ( 1 ), undergoing unusual three-step ferroelastic phase transitions from hexagonal paraelastic phase to orthorhombic, monoclinic, and triclinic ferroelastic phases at 388, 376, and 311 K, respectively, with Aizu notation of 6/ mmm F mmm , mmm F2/ m , and 2/ m F-1, featuring spontaneous strain of 0...

Inspired by creatures, abundant stimulus-responsive hydrogel actuators with diverse functionalities have been manufactured for applications in soft robotics. However, constructing a shape memory and self-sensing bilayer hydrogel actuator with high mechanical strength and strong interfacial bonding still remains a challenge. Herein, a novel bilayer hydrogel with a stimulus-responsive TEMPO-oxidized cellulose nanofibers/poly(N-isopropylacrylamide) (TOCN/PNIPAM) layer and a non-responsive TOCN/polyacrylamide (TOCN/PAM) layer is proposed as a thermosensitive actuator...

Although conductive hydrogels have been widely developed currently, their low sensitivity and poor stability severely limited their practical application in flexible wearable devices. Herein, a green "stencil" anchoring strategy was proposed in this study to engineer an ultra-stable and supersensitive hydrogel by virtue of polydopamine decorating sodium alginate molecular chains as "stencil" to anchor polyaniline as conductive component. The dispersion of polyaniline was significantly improved by the sodium alginate "stencil" in the conductive hydrogel...

Manufacturing flexible sensors with prominent mechanical properties, multifunctional sensing abilities, and remarkable self-healing capabilities remains a difficult task. In this study, a novel vanillin-modified polyacrylate (VPA), which is capable of forming green dynamic covalent crosslinking with chitosan (CS), was synthesized. The synthesized VPA was combined with mesoporous silica-modified MXene (AMS-MXene) and covalently cross-linked simultaneously with CS, resulting in the formation of a flexible composite conductive film designed for dual-mode sensors...

Natural polymer-based hydrogels have been wildly used in electronic skin, health monitoring and human motion sensing. However, the construction of hydrogel with excellent mechanical strength and electrical conductivity totally using natural polymers still faces many challenges. In this paper, gelatin and oxidized sodium carboxymethylcellulose were used to synthesize a double-network hydrogel through the dynamic Schiff base bonds. Then, the mechanical strength of the hydrogel was further enhanced by immersing it in an ammonium sulfate solution based on the Hofmeister effect between gelatin and salt...

Developing high-performance hydrogels with anti-freeze, and antimicrobial properties is crucial for the practical application of flexible sensors. In this study, we prepared silver nanoparticles (AgNPs) with aloe polysaccharide (AP) as a reducing agent. Then, the AP/AgNPs were added to a system of polyvinyl alcohol and borax crosslinked in water/glycerol to obtain a multifunctional conductive hydrogel. The incorporated AgNPs improved the conductivity (0.39 S/m) and mechanical properties (elongation at break: 732...

The field of biosensing would significantly benefit from a disruptive technology enabling flexible manufacturing of uniform electrodes. Inkjet printing holds promise for this, although realizing full electrode manufacturing with this technology remains challenging. We introduce a nitrogen-doped carboxylated graphene ink (NGA-ink) compatible with commercially available printing technologies. The water-based and additive-free NGA-ink was utilized to produce fully inkjet-printed electrodes (IPEs), which demonstrated successful electrochemical detection of the important neurotransmitter dopamine...

Flexible electronics have gained a lot of attention in recent years due to their compatibility with soft robotics, artificial arms, and many other applications. Meanwhile, the detection of acoustic frequencies is a very useful tool for applications ranging from voice recognition to machine condition monitoring. In this work, the dynamic response of Pt nanoparticles (Pt NPs)-based strain sensors on flexible substrates is investigated. the nanoparticles were grown in a vacuum by magnetron-sputtering inert-gas condensation...