Construction And Performance Of MXene-based Wearable Pressure Sensor

With the development of wearable technology,the demand for wearable pressure sensors with high sensitivity and wide working range for monitoring human movement and human-computer interaction is increasing.The performance of the sensor,such as sensitivity and service life,is closely related to the type of sensing material,structure and pore structure.Therefore,the development of efficient sensor materials has important scientific significance and practical application value.Layered MXene has high electrical conductivity,large specific surface area,excellent mechanical properties,good hydrophilicity,adjustable layer spacing and other physical and chemical properties,which makes it an excellent candidate material for force sensitive layer.It is expected to develop into a low cost and high performance pressure sensor.By combining MXene with flexible elastomer,a flexible wearable pressure sensor with excellent flexibility,high sensitivity and stability was fabricated.The main research contents and results are as follows:(1)Mxene nanosheets were successfully prepared by one step method of lithium fluoride and hydrochloric acid.On the one hand,this method can indirectly produce hydrofluoric acid to etch the precursor Max phase,which reduces the risk of experiment.In addition,there is no need to go through the intercalation agent for pre-intercalation,so the experiment procedure is simple.Finally,monolayer or less layers of Mxene nanosheets with uniform dispersion and stable structure were obtained by ultrasonic stripping.(2)Polyurethane sponge based on three-dimensional porous structure has the characteristics of high resilience and large specific surface area.The positively charged chitosan(CS)and negatively charged MXene were alternately adsorbed on the sponge framework,and a flexible,highly sensitive and washeable pressure sensor was assembled together with the electrode to construct a wearable piezoresistive pressure sensor of chitosan/MXene/PU.Meanwhile,the effects of preparation conditions and preparation methods on the performance of the device were studied.When the sponge was soaked twice in 1 mg/mL Mxene solution and 0.2 mg/mL CS solution,the sensitivity of the sponge reached 30.02 kPa-1,and it had a fast response time(282 ms),recovery time(136 ms)and good stability(2000).Based on the excellent sensing performance,the sensor can monitor the movement of human joints and pulse pulse in real time,showing the potential application of wearable pressure sensors in human body detection.(3)Herein,a CS/MXene/PU-sponge/PVA based 3D pressure sensor is developed to simultaneously achieve wearability,washability,and high sensitivity in wide region.In the force-sensitive layer of the sensor,MXene and CS are fully attached to the PU sponge,which ensures the composite sponge is remarkably conductive and washable.Benefiting from the highly resistive PVAnanowire spacer,the initial current of the sensor is reduced significantly,so the sensor exhibits extremely high sensitivity(84.9 kPa-1 for less than 5 kPa region and 140.6 kPa-1 for 5～22 kPa region).Moreover,the sensor has excellent fast response time of 200 ms and short recovery time of 30 ms,as well as nonattenuating durability over 5000 cycles.With the high sensitivity in wide range,the sensor can detect a variety of human activities in real time,ranging from the large pressure of joint activities to subtle pressure of pulse.Based on the superior performance,the sensor also demonstrates potential application in measuring pressure distribution.