Fabrication And Performance Study Of Flexible Pressure Sensing Materials Based On Shape-Memory Aerogels

Recent years have witnessed the blooming development of flexible pressure sensors for applications in human physical/physiological monitoring and personal health management due to their comprehensive characteristics of visual signal transduction,timely feedback,and remote supervision.The human body has a variety of health-related physical signals,such as pulse,blood pressure and touch,and flexible pressure sensors are important for the accurate extraction and real-time feedback of such signals over long periods.To improve the sensing performance of wearable pressure sensor devices,researchers have tried to design a variety of conductive microstructures.However,there are instabilities in the conductive microstructure of current sensing materials,both in the microstructure itself and in the material-contact interface,which may lead to the inability to achieve accurate extraction of pressure signals.In addition,the complexity of the three-dimensional shape of the contact interface is also an important factor affecting stable wear and adaptability.Therefore,it is urgent to design flexible pressure sensing materials with stable and sensitive conductive microstructures and adaptive capabilities.In response to the above problems,this paper fabricated an anisotropic conductive aerogel with shape-memory function and used it to design a flexible pressure sensor device.The anisotropic pores of the conductive aerogel are stable 3D microstructures,which satisfy the basic requirements of resistance type flexible pressure sensor devices and have high elasticity,thus enabling the pressure sensor devices to have high sensitivity and wide detection range;the shape memory function can change the shape of the aerogel and give the pressure sensor devices the ability to reprogram the shape,which can be adapted to different 3D shapes and tightly attached.Finally,to further enhance the hydrophobicity and sensitivity of the aerogel,we carried out MXene dipping and fluoride modification of the anisotropic aerogel,and the preliminary result of the study showed that the expected effect was achieved.The study contents and conclusions of this paper are as follows:1.Prepared anisotropic shape memory conductive aerogels.An anisotropic honeycomb porous aerogel(PEG/CNTs)was prepared by targeted low-temperature polymerization and freeze-drying method using polyethylene glycol diacrylate(PEGDA)and aminated carbon nanotubes(A-CNTs)as the basic raw materials.The aerogel has excellent mechanical properties in the radial direction,and the plastic deformation is only 3.74%under 100 cycles of radial compression.In addition,the aerogels were characterized by qualitative experiments and dynamic thermo-mechanical analyzer tests(DMA)to demonstrate excellent thermal/optical dual-response shape memory properties,with both shape memory recovery rate(R_r)and shape memory fixation rate(R_f)reaching over 98%.2.Following the radial design principle,a flexible pressure sensor device was assembled using anisotropic shape-memory aerogels.The device has excellent pressure response capability and adaptive shape reprogrammable performance.The experimental results show that the flexible pressure sensor device can detect a range of 0.0005-1.2 MPa with high linear sensitivity and excellent cycling stability,and can be used to detect a variety of small human physiological activities and human motion.In addition,the reprogrammable shape memory function can be used to adjust the shape of the device,and the adaptive wear and long-time monitoring of the target site can be achieved by shape programming and shape recovery.3.Hydrophobic,highly sensitive and flexible pressure sensing material(F-MXene@PEG/CNTs)was prepared using fluoride modification and MXene dipping method.The results show that the material has better hydrophobic and sensing properties and can detect smaller pressure(29 Pa).In addition,the shape-memory property can be used to achieve the tuning of the porous structure of the material by adjusting the compression amount,thus achieving the reversible tuning of the conductivity.