Wide temperature range-and damage-tolerant microsupercapacitors from salt-tolerant, anti-freezing and self-healing organohydrogel via dynamic bonds modulation

The advance of microelectronics requires the micropower of microsupercapacitors(MSCs) to possess wide temperature-and damage-tolerance beyond high areal energy density.The properties of electrolyte are crucial for MSCs to meet the above requirements.Here,an organohydrogel electrolyte,featured with high salt tolerance,ultralow freezing point,and strong self-healing ability,is experimentally realized via modulating its inner dynamic bonds.Spectroscopic and theoretical analysis reveal that dimethyl sulfoxide has the ability to reconstruct Li^(+)solvation structure,and interact with free water and polyvinyl alcohol chains via forming hydrogen bonds.The organohydrogel electrolyte is employed to build MSCs,which show a boosted energy density,promising wide temperature range-and damage-tolerant ability.These attractive features make the designed organohydrogel electrolyte have great potential to advance MSCs.

Nanofiber Composite Reinforced Organohydrogels for Multifunctional and Wearable Electronics

Composite organohydrogels have been widely used in wearable electronics.However,it remains a great challenge to develop mechanically robust and multifunctional composite organohydrogels with good dispersion of nanofillers and strong interfacial interactions.Here,multifunctional nanofiber composite reinforced organohydrogels(NCROs)are prepared.The NCRO with a sandwich-like structure possesses excellent multi-level interfacial bonding.Simultaneously,the synergistic strengthening and toughening mechanism at three different length scales endow the NCRO with outstanding mechanical properties with a tensile strength(up to 7.38±0.24 MPa),fracture strain(up to 941±17%),toughness(up to 31.59±1.53 MJ m~(-3))and fracture energy(up to 5.41±0.63 kJ m~(-2)).Moreover,the NCRO can be used for high performance electromagnetic interference shielding and strain sensing due to its high conductivity and excellent environmental tolerance such as anti-freezing performance.Remarkably,owing to the organohydrogel stabilized conductive network,the NCRO exhibits superior long-term sensing stability and durability compared to the nanofiber composite itself.This work provides new ideas for the design of high-strength,tough,stretchable,anti-freezing and conductive organohydrogels with potential applications in multifunctional and wearable electronics.

Environmentally Tough and Stretchable MXene Organohydrogel with Exceptionally Enhanced Electromagnetic Interference Shielding Performances

Conductive hydrogels have potential applications in shielding electromagnetic(EM)radiation interference in deformable and wearable electronic devices,but usually suffer from poor environmental stability and stretching-induced shielding performance degradation.Although organohydrogels can improve the environmental stability of materials,their development is at the expense of reducing electrical conductivity and thus weakening EM interference shielding ability.Here,a MXene organohydrogel is prepared which is composed of MXene network for electron conduction,binary solvent channels for ion conduction,and abundant solvent-polymer-MXene interfaces for EM wave scattering.This organohydrogel possesses excellent anti-drying ability,low-temperature tolerance,stretchability,shape adaptability,adhesion and rapid self-healing ability.Two effective strategies have been proposed to solve the problems of current organohydrogel shielding materials.By reasonably controlling the MXene content and the glycerol-water ratio in the gel,MXene organohydrogel can exhibit exceptionally enhanced EM interference shielding performances compared to MXene hydrogel due to the increased physical cross-linking density of the gel.Moreover,MXene organohydrogel shows attractive stretching-enhanced interference effectiveness,caused by the connection and parallel arrangement of MXene nanosheets.This well-designed MXene organohydrogel has potential applications in shielding EM interference in deformable and wearable electronic devices.

Self-Healing,Self-Adhesive and Stable Organohydrogel-Based Stretchable Oxygen Sensor with High Performance at Room Temperature

With the advent of the 5G era and the rise of the Internet of Things,various sensors have received unprecedented attention,especially wearable and stretchable sensors in the healthcare field.Here,a stretchable,self-healable,self-adhesive,and room-temperature oxygen sensor with excellent repeatability,a full concentration detection range(0-100%),low theoretical limit of detection(5.7 ppm),high sensitivity(0.2%/ppm),good linearity,excellent temperature,and humidity tolerances is fabricated by using polyacrylamide-chitosan(PAM-CS)double network(DN)organohydrogel as a novel transducing material.The PAM-CS DN organohydrogel is transformed from the PAM-CS composite hydrogel using a facile soaking and solvent replacement strategy.Compared with the pristine hydrogel,the DN organohydrogel displays greatly enhanced mechanical strength,moisture retention,freezing resistance,and sensitivity to oxygen.Notably,applying the tensile strain improves both the sensitivity and response speed of the organohydrogel-based oxygen sensor.Furthermore,the response to the same concentration of oxygen before and after self-healing is basically the same.Importantly,we propose an electrochemical reaction mechanism to explain the positive current shift of the oxygen sensor and corroborate this sensing mechanism through rationally designed experiments.The organohydrogel oxygen sensor is used to monitor human respiration in real-time,verifying the feasibility of its practical application.This work provides ideas for fabricating more stretchable,self-healable,self-adhesive,and high-performance gas sensors using ion-conducting organohydrogels.

Polarization-driven multifunctional organohydrogels with strain sensitivity toward electromagnetic wave absorption

Rapid advancements in flexible electronics and military applications necessitate high-performance electromagnetic wave(EMW)absorbers.While huge breakthroughs in achieving high-attenuation microwave absorption,conventional EMW absorbing materials have single function and ambiguous absorption mechanisms.Herein,numerous gel-type absorbers are fabricated by introducing“regulators”into poly(acrylamide-co-acrylic acid)(P(AM-co-AA))networks through radical polymerization in a glycerol-water mixed solvent.The dielectric constant and EMW absorption performance of the gels are precisely predicted by adjusting monomer concentration,the ratio of glycerol/water,and the content of the regulators.Notably,A_(6)G_(20)T_(20)-2 exhibits promising absorption performance with a minimum reflection loss(RL_(min))of-33.8 dB at 12.4 GHz.The effective absorption bandwidth(EAB)covers the entire X-band(8.2-12.4 GHz)at a thickness of 2.7 mm.A_(6)G_(20)T_(20)-2 also has sensitive deformation responses and excellent tensile strength,adhesiveness,self-healing and anti-freezing properties.Overall,this work not only provides insight into the polarization loss mechanism of the gels as the result of high correlation between EMW absorbing properties and molecular polarization,but also offers an important reference for developing functional protective materials because of the rich functionalities and efficient protective capabilities of the gels.

Liquid-metals-induced formation of MXene/polyacrylamide composite organohydrogels for wearable flexible electronics

Organohydrogels have demonstrated superior environmental adaptability and frost resistance compared to conventional hydrogels,thereby prompting considerable interests in the development and design of innovative organohydrogels.Herein,we report an effective one-pot method for fabricating MXene/polyacrylamide(MXene/PAM)composite organohydrogel(MAOH)by employing Ga liquid metals(Ga LMs)as a highly reactive component in the induced free radical polymerization reaction,without the need for additional heating or cross-linking agents.This synthetic protocol addresses the time-consuming and organic solvent waste concerns associated with traditional solvent displacement methods for organohydrogel preparation.The incorporation of MXene not only highly enhances the conductivity but also confers improved mechanical properties of MAOH.The MAOH exhibits excellent environmental adaptability(>7 d),sustained moisture retention,remarkable self-healing capabilities,and outstanding mechanical properties under low temperatures(-20℃).It demonstrates exceptional performance in micro-motion monitoring,rapid response time(125 ms),superior stretchability,and a broad range of strains(0.3%–600%).Therefore,the designed MAOH has great potential for applications in diverse fields such as prosthetics,electronic skin,human–machine interaction,and smart terminals.

A mechanically stable self-pumping organohydrogel dressing with aligned microchannels for accelerated diabetic wound healing

Self-pumping dressings(SPDs)have been developed as a new type of effective material for the drainage of excessive wound exudates based on the structure of asymmetric wettability.However,current SPDs are easy to lose their asymmetric wettability due to the weak interfacial mechanical stability between the hydrophobic and hydrophilic layers.Herein,we report an integrated self-pumping organohydrogel dressing with aligned microchannels(SPD-AM),prepared by an ice-templating-assisted wetting-enabled-transfer(WET)polymerization strategy,that can accelerate the healing process of diabetic wounds.The WET polymerization strategy enables strong interfacial mechanical stability between the hydrophobic organogel and hydrophilic hydrogel layers.The aligned microchannels greatly improve the draining capability of SPDs.Taking a diabetic rat model as an example,the SPD-AM can significantly reduce the bacterial colonization with low inflammatory responses,enhance dermal remodeling by about 47.31%,and shorten wound closure time by about 1/5 compared with other dressings,ultimately accelerating diabetic wound healing.This study is valuable for developing next-generation SPDs with stable mechanical performance for clinical applications.

Rapid self-healing,self-adhesive,anti-freezing,moisturizing,antibacterial and multi-stimuli-responsive PVA/starch/tea polyphenol-based composite conductive organohydrogel as flexible strain sensor

The complexity of application environment stimulates the development of wearable devices based on functional hydrogels.Among all the promising performances,self-healing and self-adhesion properties are ideal for hydrogel sensors,which can guarantee good accuracy,comfort and long service life.However,it is still a challenge to achieve simultaneous self-healing and self-adhesion in different environments(in the air,underwater and at low temperatures).Herein,a feasible new strategy was successfully carried out to prepare a starch-based composite conductive organohydrogel based on the reversible borate ester bonds formed by complexing starch/polyvinyl alcohol(PVA)/tea polyphenol(TP)with borax,and multiple hydrogen-bond interactions among PVA,starch,TP and ethylene glycol(EG).Silver nanoparticles(Ag-NPs),reduced and stabilized by TP,and MWCNTs(multi-walled carbon nanotubes)were introduced into the cross-linking networks to endow the resulting PBSTCE organohydrogel with considerable antibacterial property and conductivity,respectively.The organohydrogel possessed rapid self-healing(HE(self-healing efficiency)=96.07%in 90 s,both in the air and underwater,also at-20℃),considerable self-adhesion(both in the air and underwater,also at-20℃),remarkable stretchability(814%of elongation),anti-freezing(-20℃)and moisture-retention abilities,antibacterial activity,sensitive pH/sugar-responsiveness,and plasticity.The strain sensor formed by the PBSTCE organohydrogel can not only effectively record large-scale human motions(e.g.finger/wrist/elbow bending,walking,etc.),but also accurately capture subtle motion changes(e.g.breathing,chewing,swallowing,speaking,smiling and frowning).Moreover,the self-healed organohydrogel sensor also exhibited almost invariable mechanical,electrical and sensing behaviors.This work demonstrates a feasible strategy to construct multifunctional starch-based organohy-drogels,and promotes their efficient,stable and eco-friendly application as flexible wearable devices.

An injectable curcumin-releasing organohydrogel with non-drying property and high mechanical stability at low-temperature for expe dite d skin wound care

Although hydrogels have demonstrated great potential as new wound dressing materials,their instability in shape and/or mechanical characteristics due to water loss or freezing remains a shortcoming for wound care application.Herein,a novel injectable organohydrogel(IOH)of physically crosslinked polyvinyl alco-hol/glycerol that possesses non-drying capability and high stability at low temperature was developed for wound care.IOH has a skin-like stiffness(G’,∼280 Pa),high injectability,self-healing capability,high water-vapor transmission rate,and bacterial inhibitory effect.IOH exhibits high shape and mechanical stabilities after curing at 37°C and 50%relative humidity for 7 days or after curing at-20°C for 1 day.In addition,glycerol in IOH enabled an efficient loading and release of water-insoluble curcumin,a well-known anti-bacterial and anti-inflammation drug.The curcumin-releasing IOH(Cur-IOH)demonstrated significantly enhanced anti-bacterial performance compared to IOH or curcumin-loading polyvinyl alco-hol hydrogel.More importantly,Cur-IOH could accelerate wound healing in a murine full-thickness skin defect wound model,revealing improved wound contraction,collagen deposition,angiogenesis,and epi-dermis formation.This study demonstrates the great potential of organohydrogel for the reparation of severe wounds and Cur-IOH as a new type of injectable wound healing material.

Excitation-wavelength-dependent fluorescent organohydrogel for dynamic information anti-counterfeiting

Anti-counterfeiting labels with various fluorescent colors are of great importance in information encryption-decryption,but are still limited to static information display.Therefore,it is urgent to develop new materials and encryption-decryption logic for improving the security level of secret information.In this study,an organohydrogel made up of poly(N,N-dimethylacrylamide)(pDMA)hydrogel network and polyoctadecyl methacrylate(pSMA)organogel network that copolymerized with two fluorophores,6-acrylamidopicolinic acid moieties(6APA,fluorescent ligand)and spiropyran units(SPMA,photochromic monomer),was prepared by a two-step interpenetrating method.As UV light of 365nm and 254nm can both cleave C_(spiro)-O bonds of SPMA,and the green fluorescence of 6APA-Tb^(3+) can only be excited by 254nm light,the organohydrogel displays yellow and red under the irradiation of 254nm and 365 nm,respectively.In addition to wavelength selectivity,these two fluorophores are thermal-responsive,leading to the fluorescence variation of the organohydrogel during heating process.As a result,secret information loaded on the organohydrogel can be decrypted by the irradiation of UV light,and the authenticity of the information can be further identified by thermal stimulation.Our fluorescent organohydrogel can act as an effective anti-counterfeiting label to improve the information security and protect the information from being cracked.

Transient Chemical Activation of Covalent Bonds for Healing of Kinetically Stable and Multifunctional Organohydrogels

It remains a great challenge to balance the kinetic stability and intrinsic healing ability of polymer materials.Here,we present an efficient strategy of using a synthetic reaction cycle to regulate the intrinsic healing ability of thermodynamically stable and kinetically inert multifunctional organohydrogels.By combining a double decomposition reaction with spontaneous energy dissipation,we can construct the simplest synthetic reaction cycle that can induce a transient out-of-equilibrium state for achieving the healing of organohydrogels with kinetically locked acylhydrazone bonds.In addition to balancing kinetic stability and healing ability,the synthetic reaction cycle also enables the polymer materials to have high tolerance to organic solvents,high ionic strength,high and low temperatures,and other harsh conditions.Therefore,the kinetically stable and healable organohydrogels remain mechanically flexible and electrically conductive even down to−40°C and are readily recyclable.The integration of chemical networks into healable polymers may provide novel,versatile materials for building next-generation electronic devices.

Self-healable, recyclable, ultrastretchable, and high-performanceNO_(2) sensors based on an organohydrogel for room and sub-zero temperature and wireless operation

To date,development of high-performance,stretchable gas sensors operating at and below room temperature(RT)remains a challenge in terms of traditional sensing materials.Herein,we report on a high-performance NO_(2) gas sensor based on a self-healable,recyclable,ultrastretchable,and stable polyvinyl alcohol–cellulose nanofibril double-network organohydrogel,which features ultrahigh sensitivity(372%/ppm),low limit of detection(2.23 ppb),relatively fast response and recovery time(41/144 s for 250 ppb NO_(2)),good selectivity against interfering gases(NH3,CO_(2),ethanol,and acetone),excellent reversibility,repeatability,and long-term stability at RT or even at−20°C.In particular,this sensor shows outstanding stability against large deformations and mechanical damages so that it works normally after rapid self-healing or remolding after undergoing mechanical damage without significant performance degradation,which has major advantages compared to state-of-the-art gas sensors.The high NO_(2) sensitivity and selectivity are attributed to the selective redox reactions at the threephase interface of gas,gel,and electrode,which is even boosted by applying tensile strain.With a specific electrical circuit design,a wireless NO_(2) alarm system based on this sensor is created to enable continuous,real-time,and wireless NO_(2) detection to avoid the risk of exposure to NO_(2) higher than threshold concentrations.

MXene-enhanced environmentally stable organohydrogel ionic diode toward harvesting ultralow-frequency mechanical energy and moisture energy

With the accelerating advancement of distributed sensors and portable electronic devices in the era of big data,harvesting energy from the surrounding environment to power electrical devices has become increasingly attractive.However,most mechanical energy harvesters often require high operating frequencies to function properly.Moreover,for practical applications,the survivability of devices in harsh operating environments is a vital issuewhich must be addressed.Besides,the single-stimulus responsiveness limits their further applications in complex external environments.Here,a pressure and moisture dual-responsive ionic diode consisting of two organohydrogels with opposite charges as an energy harvester is proposed.The organohydrogel ionic diode utilizes the migration of cations and anions to form the depletion zone and followed by an enhancement of the built-in potential along the depletion zone as a result of mechanical stress or humidity,converting ultralow-frequency mechanical energy or moisture energy into electrical energy.Meanwhile,this mechanism is further confirmed by the finite element analysis.With the increased rectification ratio due to the introduction of MXene,the ionic diode exhibits a relatively large output current(∼10.10μA cm^(−2))and power density(∼0.10μW cm^(−2))at a mechanical pressure of 0.01 Hz,outperforming most currently available mechanical energy harvesters.More impressively,the incorporation of ethylene glycol provides the hydrogel ionic diode with excellent temperature tolerance and long-term environmental stability.The organohydrogel ionic diode can also be applied as a moisture-driven power generator and self-powered humidity sensor.This study presents promising prospects for the efficient collection of renewable and sustainable energy and the practical application of hydrogel-based energy harvesters in extreme environments.

Highly transparent, antifreezing and stretchable conductive organohydrogels for strain and pressure sensors

Conductive hydrogels are good candidates for flexible wearable sensors, which have received considerable attention for use in human-machine interfaces, human motion/health monitoring, and soft robots. However, these hydrogels often freeze at low temperatures and thus, exhibit low transparency, weak mechanical strength and stretchability, as well as poor adhesion strength.In this paper, conductive organohydrogels were prepared by thermal polymerization of acrylamide and N-(3-aminopropyl)methacrylamide in a glycerol-water binary solvent using Na Cl as a conductive salt. Compared to other organohydrogels, our organohydrogels featured higher fracture stress(170 kPa) and greater stretchability(900%). The organohydrogels showed excellent antifreezing properties and high transparency(97%, at 400–800 nm wavelength) and presented outstanding adhesion strength to a variety of substrates. The conductive organohydrogels that were stored at -20℃ for 24 h could still respond to both strain and pressure, showing a high sensitivity(gauge factor=2.73 under 100% strain), fast response time(0.4 s), and signal repeatability during multiple force cycles(~100 cycles). Furthermore, the conductivity of cleaved antifreezing gels could be restored by contacting the broken surfaces together. Finally, we used our organohydrogels to monitor human tremors and bradykinesia in real-time within wired and wireless models, thus presenting a potential application for Parkinson’s disease diagnosis.

Transparent,stretchable and anti-freezing hybrid double-network organohydrogels

Stretchable ionic conductors with high transparency and excellent resilience are highly desired for flexible electronics,but traditional ionic conductive hydrogels are easy to dry and freeze.Herein,a newly hybrid crosslinking strategy is presented for preparing a stretchable and transparent hydrogel by using sodium alginate(SA)and acrylamide based on the unique physically and covalently hybrid crosslinking mechanism,which is transformed into organohydrogel by simple solvent replacement.Due to the combination of hybrid crosslinking double network and hydrogen bond interactions introduced by the glycerin-water binary solvent,the SA-poly(acrylamide)-organohydrogel(SPOH)demonstrates excellent anti-freezing(-20℃)property,stability(>2 days),transparency,stretchability(~1600%)and high ionic conductivity(17.1 mS cm^(-1)).Thus,a triboelectric nanogenerator made from SPOH(O-TENG)shows an instantaneous peak power density of 262 mW m^(-2)at a load resistance of 10 MΩand efficiently harvests biomechanical energy to drive an electronic watch and light-emitting diode.Moreover,The O-TENG exhibits favorable long-term stability(2 weeks)and temperature tolerance(-20℃).In addition,the raw materials can be prepared into SPOH fibers by a simple tubular mold method,exhibiting high transparency,which can be used for laser transmission.The various abilities of the SPOH promise the application of energy harvesting and laser transmission for wearable electronics and biomedical field.

Oil-polluted water purification via the carbon-nanotubes-doped organohydrogel platform

Solar-driven evaporators are promising for tackling freshwater scarcity but still challenged in simultaneously realizing comprehensive performances at one platform for sustainable and efficient application in real-world environments,such as stablefloating,scalability,salt-resistance,efficient vaporization,and anti-oil-fouling property.Herein,we design a hybrid organohydrogel evaporator to achieve the enduring oil contamination repulsion with maintaining accelerated evaporation process,and integrate capacities of ultra-stable floating,hindered salt-crystallization,large-scale fabrication for practical purification of seawater and polluted solutions.The raised water surface surrounding evaporators,induced by low density of organogel-phase,results in oil contamination resistance through the lateral capillary repulsion effect.Meanwhile,the organogel-phase containing photo-thermal carbon-nanotubes with low thermal capacity and conduction can form locally confined hot dots under solar irradiation and reduce heat dissipation on heating excessive water.Therefore,based on this approach,accelerated long-term practical purification of oilcontaminated solutions without any extra disposal is realized.Considering other properties of ultra-stable floating,large-scale fabrication,and anti-salt crystallization,these innovative organohydrogel evaporators open pathways for purifying oil-slickpolluted water via interfacial evaporation and are anticipated accelerating industrialization of efficient and sustainable solar-driven water purification.

Magnetic-programmable organohydrogels with reconfigurable network for mechanical homeostasis

Synthetic materials with tunable mechanical properties have great potential in soft robotics and biomedical engineering.However,current materials are limited to the mechanical duality altering their mechanical properties only between soft and hard states and lack of consecutively programmable mechanics.Herein,the magnetic-programmable organohydrogels with heterogeneous dynamic architecture are designed by encasing oleophilic ferrofluid droplets into hydrogel matrix.As magnetic field increases,the mechanical properties of organohydrogels can be consecutively modulated owing to the gradual formation of chain-like assembly structures of nanoparticles.The storage modulus G'increases by 2.5 times when magnetic field goes up to 0.35 T.Small-Angle X-ray Scattering(SAXS)confirms the reconfigurable orientation of nanoparticles and the organohydrogels show reversible modulus switching.Besides,the materials also exhibit high stretchability,magnetic actuation behavior and effective self-healing capability.Furthermore,the organohydrogels are applied into the design of effectors with mechanical adaptivity.When subjected to serious external perturbations,the effector can maintain mechanical homeostasis by regulating modulus of organohydrogel under applied magnetic field.Such materials are applicable to homeostatic systems with mechanically adaptive behaviors and programmed responses to external force stimuli.

A flexible organohydrogel-based humidity sensor for noncontact artificial sensation

In this paper,we propose a simple organohydrogel based capacitive humidity sensor for noncontact artificial sensation applications.The sensor is simple in design and consists of a transparent polyacrylamide organohydrogel thin film attached on a flexible inter-digit electrode layer.The process of water absorption and desorption is reversible,thus the dielectric of the organohydrogel film as well as the overall capacitance is dependent on environmental humidity.The water absorption capacity and structural reliability of the device have been largely improved by adding glycerol in the organohydrogel network.By optimizing both the glycerol concentration and organohydrogel film thickness,the sensor can respond to cyclic humidity changes in a period of 300 ms.In addition,this sensor achieves a high relative capacitance increase(by 20 folds)in a wide relative humidity range(12%-95%).The sensor also exhibits high stability under different bending curvatures(up to 6.81 mm),wide temperature changes(20℃-40℃)and external pressures(0-8 N).To demonstrate the applications in wearable electronics,we found that the sensor was successful in detecting respiration intensity and rate as well as the difference in moisture content in various objects,i.e.,human skin and leaf surface.This sensor is highly sensitive and can be useful in the detection of the widerange of humidity changes.

有机凝胶肌电电极制备及其在动态手势识别的应用

为了解决传统肌电电极与皮肤贴合度不佳,易造成运动伪影的问题,本文提出一种高离子导电、良好自黏附的有机凝胶作为电极检测肌电信号,并将其应用于动态手势动作的识别。首先,采用物理交联与化学交联结合的互贯穿网络结构,在生物相容性的聚丙烯酰胺/海藻酸钠体系中加入单宁酸、氯化钠和甘油,获得聚丙烯酰胺/海藻酸钠/单宁酸有机凝胶;其次,测试制备的有机凝胶力学、导电及黏附等性能,并将其作为皮肤表面电极进行肌电信号的检测;最后,使用卷积神经网络算法将其应用于动态手势动作的识别。研究结果表明:制备的有机凝胶具有低弹性模量以及可逆自黏附能力,可实现与皮肤的保形黏附;有机凝胶具有7.7 kPa的弹性模量、310%的伸长率、2.81 mS/cm的离子导电率,并具有良好的自黏附性能以及可降解性,能够获得17.14 dB信噪比的高质量肌电信号,能够有效识别不同界面操作的动态动作及手语手势,平均识别率分别达95.04%和98.67%。该有机凝胶电极具有高信噪比,可有效识别动态手势,在人机交互、机器人遥操作领域具有广阔的应用前景。

A green MXene-based organohydrogel with tunable mechanics and freezing tolerance for wearable strain sensors

Conductive hydrogels have attracted considerable attention owing to their potential for use as electronic skin and sensors.However,the loss of the inherent elasticity or conductivity in cold environments severely limits their working conditions.Generally,organic solvents or inorganic salts can be incorporated into hydrogels as cryoprotectants.However,their toxicity and/or corrosive nature as well as the significant water loss during the solvent exchange present serious difficulties.Herein,a liquid-like yet non-toxic polymer-polyethylene glycol(PEG) was attempted as one of the components of solvent for hydrogels.In the premixed PEG-water hybrid solvent,polyacrylamide(PAAm) was in situ polymerized,overcoming the inevitable water loss induced by the high osmotic pressure of the PEG solution and achieving tailored water capacity.Interestingly,the mechanical strength( "soft-to-rigid" transition) and anti-freezing properties of organohydrogels can be simultaneously tuned over a very wide range through adjusting PEG content.This was due to that with increasing PEG in solvent,the PAAm chains transformed from stretching to curling conformation,while PEG bonded with water molecules via hydrogen bonds,weakening the crystallization of water at subzero temperature.Additionally,a highly conductive Ti_(3)C_(2)T_(x)-MXene was further introduced into the organohydrogels,achieving a uniform distribution triggered by the attractive interaction between the rich functional groups of the nanofillers and the polymer chains.The nanocomposite hydrogels demonstrate high electrical conductivity and strain sensitivity,along with a wide working temperature window.Such a material can be used for monitoring human joint movement even at low temperature and has potential applications in wearable strain sensors.