Synchronous deprotonation–protonation for mechanically robust chitin/aramid nanofibers conductive aerogel with excellent pressure sensing, thermal management, and electromagnetic interference shielding

Aerogels with regularly porous structure and uniformly distributed conductive networks have received extensive attention in wearable electronic sensors,electromagnetic shielding,and so on.However,the poor mechanical properties of the emerging nanofibers-based aerogels are limited in practical applications.In this work,we developed a synchronous deprotonation–protonation method in the KOH/dimethyl sulfoxide(DMSO)system at room temperature for achieving chitin cross-linked aramid nanofibers(CANFs)rather than chitin nanofibers(ChNFs)and aramid nanofibers(ANFs)separately by using chitin and aramid pulp as raw materials.After freeze-drying process,the cross-linked chitin/aramid nanofibers(CA)aerogel exhibited the synergetic properties of ChNF and ANF by the dual-nanofiber compensation strategy.The mechanical stress of CA aerogel was 170 kPa at 80%compressive strain,increased by 750%compared with pure ChNF aerogel.Similarly,the compressibility of CA aerogel was somewhat improved compared to ANF aerogel.The enhancement verified that the crosslinking reaction between ANF and ChNF during the synchronous deprotonation process was formed.Afterwards,the conductive aerogels with uniform porous structure(CA-M)were successfully obtained by vacuum impregnating CA aerogels in Ti_(3)C_(2)T_(x) MXene solution,displaying low thermal conductivity(0.01 W/(m·K)),high electromagnetic interference(EMI)shielding effectiveness(SE)(75 dB),flame retardant,and heat insulation.Meanwhile,the as-obtained CA-M aerogels were also applied as a pressure sensor with excellent compression cycle stability and superior human motion monitoring capabilities.As a result,the dual-nanofiber based conductive aerogels have great potentials in flexible/wearable electronics,EMI shielding,flame retardant,and heat insulation.

Durable and Flexible Bio-assembled RGO-BC/BC Bilayer Electrodes for Pressure Sensing

The new generation of electronics tends to be well-performed,facile and environmentally friendly.Here,we report a bio-assembled sensitive pressure senor based on reduced graphene oxide-bacterial cellulose/bacterial cellulose(RGO-BC/BC)bilayer films,integrated by bacteria in one step.The advantage of this integration is that there is strong nanofiber connection between the conductive RGO-BC and insulative highly compressible porous BC layer,which confers RGO-BC/BC film electrode with good robustness,tailorability,flexibility and wearability.Without extra bonding-interface or postprocessing,the RGO-BC/BC bilayer films could be directly assembled into pressure sensing devices.Ascribed from the good reversible compressibility of the BC layer and incorporated bilayer structure,the pressure sensor performs good sensitivity and excellent durability and bending stability.The facile sensitive capacitive sensor could monitor the human hand or finger motion in real time.The sensing array is able to detect the spatial distribution of pressure mounted in the flat plane as well as curved surface of human body,succeeding in the correction of human walking posture for health care.The e-skins are potential in wearable electronics,artificial intelligence,soft robots,healthcare etc.

Soft piezoresistive pressure sensing matrix from copper nanowires composite aerogel

We report on a simple yet efficient approach to fabricate soft piezoresistive pressure sensors using copper nanowires-based aerogels.The sensors exhibit excellent sensitivity and durability and can be easily scalable to form large-area sensing matrix for pressure mapping.This opens a low-cost strategy to wearable biomedical sensors.

Vapor and Pressure Sensors Based on Cellulose Nanofibers and Carbon Nanotubes Aerogel with Thermoelectric Properties

In this work,thermally insulating and electrically conductive aerogels were prepared from cellulose nanofibers(CNF)and carbon nanotubes(CNTs)by environmentally friendly freeze-drying process.The thermal conductivity of neat CNF aerogel is 24 mW/(m・K)with a density of 0.025 g/cm3.With the addition of CNTs into CNF aerogel,the electrical conductivity was significantly increased while the thermal conductivity was increased to 38 mW/(m・K).Due to these interesting properties,the Seebeck coefficient and the figure of merit(ZT)of the CNF/CNTs aerogels were measured and showed that CNF/CNTs aerogel thermoelectric properties can be improved.The compressibility and electrical resistance of the CNF/CNTs aerogel highlighted its pressure-responsive property.A set of volatile organic compounds(VOCs)were exposed to aerogels to monitor the resistance change.The CNF/CNTs aerogel showed high sensitivity and good response to both nonpolar and polar vapors due to the absorption by both CNF and CNTs networks.The prepared CNF/CNTs aerogel is therefore a good candidate for thermal insulation,thermoelectric material,VOCs sensing,and pressure-sensing applications.

Fiber Bragg Grating Pressure Sensor Based on Corrugated Diaphragm

A kind of fiber Bragg grating pressure sensor based on corrugated diaphragm is proposed. The relationship between the central wavelength of reflective wave of FBG and pressure is given, and the expression of the pressure sensitivity coefficient is also given. Within the range from 0 MPa to 0.3 MPa, the experimental pressure sensitivity is 7.83 nm/MPa, which is 2 610 times than that of the bare fiber grating. The experimental results agree with the theoretical analysis. It is indicated that the expected pressure sensitivity of the sensor can be obtained by optimizing the size and mechanical parameters of the corrugated diaphragm.

Optical properties of Nd^(3+) ions doped GdTaO_(4) for pressure and temperature sensing

Pressure-and temperature-dependent luminescence properties of ^(3)F_(3/2)→^(4)I9/2 transition of Nd^(3+):GdTaO_(4) were studied for potential applications in optical sensing.Two isolated emission lines corresponding to^(3)F_(3/2)(R2,1)→^(4)I_(9/2)(Z5)transitions,located at 920 and 927 nm under ambient condition,are very sensitive to pressure with coefficients of-15.6 and-14.5 cm^(-1)/GPa determined in a pressure range up to about 9 GPa.The luminescence intensity ratio between the two emission lines exhibits a large dependence with temperature in a range from 80 to 620 K,the corresponding temperature sensitivity at room temperature is similar to that of Nd^(3+):YAG.These advantages,together with the other observed features of high stable position relationship under pressure and low thermal shifts for the two emission lines indicate that Nd^(3+):GdTaO_(4) is a promising candidate to be used as pressure and temperature sensors in the near-infrared spectral range.

Direct stamping multifunctional tactile sensor for pressure and temperature sensing

Flexible and wearable sensors have broad application prospects in health monitoring and artificial intelligence.Many different single-functional sensing devices have been developed in recent years,such as pressure sensors and temperature sensors.However,it is still a great challenge to design and fabricate tactile sensors with multiple sensing functions.Herein,we propose a simple direct stamping method for the fabrication of multifunctional tactile sensors.It can detect pressure and temperature stimuli signals simultaneously.This pressure/temperature sensor possesses high sensitivity(0.67 kPa^(-1)),large linear range(0.75-5 kPa),and fast response speed(15.6 ms)in pressure sensing.It also has a high temperature sensitivity(1.41%/℃)and great linearity(0.99)for temperature sensing in the range of-30 to 30℃.All these excellent performances indicate that this pressure/temperature sensor has great potential in applications for artificial intelligence and health monitoring.

Nanogenerator-based bidirectional pressure sensor array and its demonstration in underwater invasive species detection

Lakes areas,which cause catastrophic damages in both commercial fishery and ecological systems.However,current assessment strategies may pose challenges for lake-wide abundance estimation and non-target anadromous species preservation.Here,we demonstrate an efficacious species-specific non-destructive sensing system based on porous ferroelectret nanogenerator for in-situ monitoring of lamprey spawning migration using their unique suction behavior.Simulations show that the porous structure enables a redistribution of surface charges under bidirectional deformations,which allows the detection of both positive and negative pressures.The quasi-piezoelectric effect is further validated by quantitative analysis in a wide pressure range of−50 to 60 kPa,providing detailed insights into transduction working principles.For reliable lamprey detection,a 4×4-pixel sensor array is developed and integrated with a complementary metal-oxide-semiconductor(CMOS)based signal processing array thus constituting a sensing panel capable of recording oral suction patterns in an underwater environment.

Multistage Microstructured Ionic Skin for Real-Time Vital Signs Monitoring and Human-Machine Interaction

Skin-like electronics research aiming to mimic even surpass human-like specific tactile cognition by operating perception-to-cognition-to-feedback of stimulus to build intelligent cognition systems for certain imperceptible or inappreciable signals was so attractive.Herein,we constructed an all-in-one tri-modal pressure sensing wearable device to address the issue of power supply by integrating multistage microstructured ionic skin(MM i-skin)and thermoelectric self-power staffs,which exhibits high sensitivity simultaneously.The MM i-skin with multi-stage“interlocked”configurations achieved precise recognition of subtle signals,where the sensitivity reached up to 3.95 kPa^(−1),as well as response time of 46 ms,cyclic stability(over 1500 cycles),a wide detection range of 0–200 kPa.Furthermore,we developed the thermoelectricity nanogenerator,piezoelectricity nanogenerator,and piezocapacitive sensing as an integrated tri-modal pressure sensing,denoted as P-iskin,T-iskin,and C-iskin,respectively.This multifunctional ionic skin enables real-time monitoring of weak body signals,rehab guidance,and robotic motion recognition,demonstrating potential for Internet of things(IoT)applications involving the artificial intelligence-motivated sapiential healthcare Internet(SHI)and widely distributed human-machine interaction(HMI).

A flexible dual-function capacitive sensor enhanced by looppatterned fibrous electrode and doped dielectric pillars for spatial perception

The integrated perception capable of detecting and monitoring varieties of activities is one of the ultimate purposes of wearable electronics and intelligent robots.Limited by the space occupation,it lacks practical feasibility to stack multiple types of single sensors on each other.Herein,a high-sensitivity dual-function capacitive sensor with proximity sensing and pressure sensing is proposed.The fringing electric field can be confined in the proximity-sensitive area by fibrous loop-patterned electrode,leading to more stolen charges when object approaching and thus a high proximity sensitivity.The high-permittivity doped structured dielectric layer reduces the compressive stiffness and enhances the rate of compression-caused increase in the equivalent relative permittivity of the dielectric layer,resulting in a larger increase in capacitance and thus a high pressure sensitivity.The electrodes and dielectric layer together compose the capacitor and act as the sensor without taking up additional space.The decoupling of proximity-sensing and pressure-sensing modes can be achieved by decrease or increase in capacitance.Combined with array distribution and sequential scanning,the sensors can be used for detection of motion trajectory,contour recognition,pressure distribution.

Stretchable multifunctional sensor based on porous silver nanowire/silicone rubber conductive film

As one of the promising human–machine interfaces,wearable sensors play an important role in modern society,which advances the development of wearable fields,especially in the promising applications of electronic skin(e-skin),robotics,prosthetics,healthcare.In the last decades,wearable sensors tend to be capable of attractive capabilities such as miniaturization,multifunction,smart integration,wearable properties such as lightweight,flexibility,stretchability,conformability for wider applications.In this work,we developed a stretchable multifunctional sensor based on porous silver nanowire/silicone rubber conductive film(P-AgNW/SR).Its unique structural configuration,i.e.,an assembly of the P-AgNW/SR with good conductivity,stability,resistance response,the insulated silicone rubber layer,provided the feasibility for realizing multiple sensing capabilities.Specifically,porous microstructures of the P-AgNW/SR made the device to be used for pressure sensing,exhibiting outstanding dynamic and static resistive responsive behaviors and having a maximum sensitivity of 9.062%∙N^(−1) in a continuous compressive force range of~16 N.With the merit of the good piezoresistive property of AgNW/SR networks embedded into the surface of micropores of the P-AgNW/SR,the device was verified to be a temperature sensor for detecting temperature changes in the human body and environment.The temperature sensor had good sensitivity of 0.844%∙℃^(−1),high linearity of 0.999 in the range of 25–125℃,remarkable dynamic stability.Besides,the developed sensor was demonstrated to be a single electrode-triboelectric sensor for active sensing,owing to the unique assembly of the conductive PAgNW/SR electrode and the silicone rubber friction layer.Based on the coupling effect of the triboelectrification and electrostatic induction,the generated electrical signals could be used to sense the human motions,according to the quantitative correlation between the human motions and the features in amplitude and waveform of the output signals.Thus,the developed stretchable sensor successfully achieved the integration of two types of passive sensing capabilities,i.e.,pressure and temperature sensing,and one type of active sensing capability,i.e.,triboelectric sensing,demonstrating the feasibility of monitoring multiple variables of the human body and environment.

A waterproof and breathable Cotton/rGO/CNT composite for constructing a layer-by-layer structured multifunctional flexible sensor

Developing a cotton fabric sensing layer with good waterproofness and breathability via a low-cost and eco-friendly method is increasingly important for the construction of comfortable and wearable electronic devices.Herein,a waterproof and breathable cotton fabric composite decorated by reduced graphene oxide(rGO)and carbon nanotube(CNT),Cotton/rGO/CNT,is reported by a facile solution infiltration method,and we adopt such Cotton/rGO/CNT composite to develop a layer-by-layer structured multifunctional flexible sensor,enabling the high-sensitivity detection of pressure and temperature stimulus.Particularly,the multifunctional flexible sensor exhibits a high response toward tiny pressure,demonstrating salient superiority in the continuous and reliable monitoring of human physiological information.Concerning temperature sensing,a good linear response for the temperatures ranging from 28 to 40℃ is achieved by the multifunctional flexible sensor and gives rise to be successfully applied to the non-contact real-time monitoring of human respiration signal.Finally,an array consisting of multifunctional flexible sensors further demonstrates its feasibility in perceiving and mapping the pressure and temperature information of contact objects.This work provides a feasible strategy for designing cotton-based sensing layers that can effectively resist liquid water penetration and allow water vapor transmission,and offers reasonable insight for constructing comfort and multifunctional wearable electronics.