Preparation Of Flexible Temperature/Pressure Dual Mode Sensors And Their Multifunctional Applications

Flexible temperature and pressure sensors play a vital role in the perception of environmental stimuli and human physiological data,finding widespread utility in applications such as environmental monitoring,disaster prevention,safety alarms,electronic skin and human-machine interfaces.However,existing flexible sensors are predominantly designed for single-parameter sensing,limiting their capacity to meet the increasing demands for integrated and multifunctional electronics.It is imperative to develop highly integrated flexible sensors to foster the evolution of intelligent and digital societies.This study aims to address the challenges encountered by temperature and pressure detection devices,including limitations in the sensing mechanism leading to potential interference and coupling of output signals under multi-physical field stimuli,complexities associated with upscaling of fabrication and molding processes,and low measurement accuracy limiting their use in demanding scenarios.Through material selection and structural design,a series of porous composite materials with excellent thermoelectric and piezo-resistive properties have been fabricated by template sacrificing,surface modification,vacuum impregnation and bidirectional freezing.The bimodal working mechanism of the sensor is illustrated using multi-physics field simulation and first-principles calculation.Machine learning classification algorithms are employed to promote the intelligent process of the sensors.This paper provides reliable solution strategies for the development of integrated electronics,and the main research contents and results of the paper are as follows:（1）Fabrication of PEDOT:PSS/CNT-based temperature/pressure dual-mode sensors with composite foam structure and their applications:To address the challenges arising from signal interference and coupling in traditional temperature/pressure sensors,which typically rely on thermoelectric and piezoresistive effects to sense multiple physical stimuli simultaneously,a strategy of combining thermoelectric technology with compressible electronic technology is proposed to convert the temperature and pressure inputs into independent voltage and resistance outs via the Seebeck and piezoresistive effects.Specifically,A dual-modal PCPP temperature/pressure sensor,adept at concurrently sensing changes in temperature and pressure devoid of signal interference,is fabricated by vacuum-assisted impregnation of PEDOT:PSS/CNT onto a polydopamine（PDA）-surface-modified PDMS foam skeleton.This design capitalizes on the energy filtering effect between PEDOT:PSS and CNT to endow the sensor with superior thermoelectric and electrical properties,while the surface modification with PDA enhances the interfacial interaction between PDMS and the conductive network of PEDOT:PSS/CNT.Furthermore,the integration of PDMS foam not only imparts low thermal conductivity but also high elasticity,ensuring reliable and efficient temperature and pressure sensing.The PCPP sensor has excellent performance in both temperature and pressure sensing:it boasts a Seebeck coefficient of 40.5μV K^-1,with a minimum detectable temperature threshold of 0.05 K,and exhibits rapid response,broad detection range,and stability over 5000 cycles for pressure sensing.The dual-response mechanism of the PCPP sensor enables synchronous detection of temperature and pressure stimuli without signal coupling,corroborated by experimental observations and Multiphysics field simulation calculations.Exploiting this dual-mode sensing mechanism,a self-powered pressure detection system and an electronic skin array based on the PCPP sensor is further engineered,paving the way for its application in advanced functional devices.（2）Fabrication of MXene-based temperature/pressure dual-mode sensors with composite foam structure and their applications:A new strategy has been proposed to address the challenge of creating easy,scalable,and cost-effective bimodal temperature/pressure sensing devices using traditional active materials,involving using Ti₃C₂T_x MXene as the only active material and combining it with a flexible low thermal conductivity substrate,enabling the production of multi-species and scalable bimodal temperature/pressure sensors.A dual-mode MCP temperature/pressure sensor is created by impregnating MXene on chitosan surface-modified PDMS foam with vacuum assistance,followed by electrode assembly.The two-dimensional nanomaterial MXene combines excellent thermoelectric properties,metallic conductivity,and a hydrophilic surface,making it an ideal candidate for bimodal temperature/pressure sensing;the CS surface modification allows MXene to bind tightly to the PDMS foam skeleton via electrostatic interaction and hydrogen bonding to form a complete conductive pathway.The MCP sensor is capable of detecting and distinguishing temperature and pressure stimuli accurately without cross-interference in the output electrical signals.It has an ultra-low detection limit（0.05 K）,high signal-to-noise ratio,and excellent cyclic stability for temperature sensing.For pressure detection,it exhibits superior sensitivity,fast response time,and outstanding durability.The sensing mechanism is further visualized by theoretical calculations（finite element analysis and first-principles calculations）,which show that the combination of the highly continuous MXene conductive network with the thermally insulating,elastic and porous structure is a key factor in ensuring excellent sensing performance,and that the intrinsic mechanism of the temperature/pressure decoupling response originates from the pressure-independent energy bands of MXene.Electronic skins and multimodal input terminals are constructed using the MCP sensor arrays,demonstrating the great potential of the sensor for applications in robotics and human-machine interaction.Additionally,various types of bimodal temperature/pressure sensors are successfully fabricated by combining numerous other types of porous elastic substrates with MXene,demonstrating the highly scalable nature of the proposed fabrication strategy.（3）Fabrication of CNT/PEDOT:PSS-based temperature/pressure dual-mode sensors with lamellar aerogel structure and their applications:The low detection resolution in current dual-mode temperature/pressure sensors poses a challenge for their use in high-demand application scenarios,and to address this issue,a method is proposed to enhance the detection resolution of the sensors through the utilization of lamellar aerogel structures.In addition,a new strategy for non-contact information transfer using invisible thermal radiation and the Seebeck effect is proposed for the first time.Composite thermoelectric aerogel（CPN）with PEDOT:PSS/SWCNT as the sensing active material and cellulose as the backbone is fabricated by bidirectional freezing and freeze-drying process,which exhibits low thermal conductivity,high elasticity,and light weight.The bidirectional freezing process endows the aerogel with a long-range ordered lamellar structure,and compared to the random porous structure,the CPN aerogel exhibits lower thermal conductivity and weaker mechanical strength in the direction perpendicular to the lamellae,enabling the aerogel-based sensor to detect smaller temperature gradients（0.02 K）and weaker pressure stimuli（12 Pa）.Taking advantage of the high-temperature detection resolution of the CPN sensor,this research achieves the non-contact extraction,decoding,and transmission of large-capacity encrypted information by using regular thermal radiation as the information carrier,the Seebeck effect as the working mechanism,the CPN sensor array as the communication interface,and the"ternary"as the encoding method.Benefiting from the characteristics of thermoelectric temperature sensing,such an information transmission strategy is not interfered with by external factors such as pressure and humidity.In addition,CPN sensor arrays can be used in contactless input interfaces to track finger movements and achieve 100%accurate recognition of finger trajectories with the assistance of machine learning.With the dual-mode sensing capability of the CPN sensor,a contact e-skin can be designed to further expand the application scenarios of the sensor.