Preparation And Properties Of Poly(acrylamide)Hydrogel Flexible Strain Sensor

The flexible strain sensor is a widely used in sensing mechanism designed to detect physical variables.It uses the geometric deformation of the flexible strain material under the action of external force to convert mechanical signals into electrical signals for detection,it has a simple transformation mechanism,low power consumption,flexible folding etc.It is developed for rapid response to sensitive signals such as pressure or stretching,and has been applied in the fields of robotics,medicine,flexible wearable health intelligent monitoring and others.However,due to the limitations of developing flexible strained materials,the main strategy for trying to achieve flexibility is not to develop new materials,but to design structures from existing materials,which brings great difficulties to the practical applicability of strained materials.The conductive hydrogel is an ideal substitute for flexible electronic devices own to its remarkable biological properties,good electrical properties,adjustable mechanical flexibility and easy processing.At the same time,conductive hydrogel materials have an attractive advantage in improving the performance of flexible strain sensors.Although the preparation method of conductive hydrogel materials is quite mature,the complex preparation steps,long period,poor mechanical properties and electrical conductivity are still the problems that hinder the commercial application of hydrogel materials.Based on these fiaws,the polyacrylamide/poly(3,4-thiophene ethylene 2 oxygen radicals)-poly(styrene sulfonic acid)(PAM/PEDOT:PSS)hydrogel was prepared by chemical cross-linking,and the polyacrylamide/mercaptosuccinic acid/poly(3,4-thiophene ethylene 2 oxygen radicals)-poly(styrene sulfonic acid)(PAM-MSA/PEDOT:PSS)hydrogel was prepared by the physical cross-linking method in this paper,and then the application of hydrogel to flexible strain sensors mainly focuses on how to quickly prepare hydrogel materials with excellent mechanical properties and electrical conductivity.The main research contents are as follows:(1)Using acrylamide(AM),poly(3,4-thiophene ethylene 2 oxygen radicals)-poly(styrene sulfonic acid)(PEDOT:PSS)as raw materials,PAM/PEDOT was prepared by chemical cross-linking method:PSS conductive hydrogel,and was applied to flexible strain sensor field.PAM/PEDOT:PSS hydrogel has a relatively dense three-dimensional network channel,which is conducive to the transmission of ions as a conductive pathway.The electrical conductivity of the hydrogel can reach 1.37 S/m,the tensile strength is 80 kPa,the elongation at break is 601%,and toughness reaches is 301 kJ/m3.The hydrogel strain sensor can accurately detect human motion signals,and the response time is only(110 ms).(2)Using glutathione(GSH)and mercaptosuccinic acid(MSA)as initiators to initiate the polymerization of acrylamide to prepare PAM-GSH and PAM-MSA mixtures.Fourier infrared spectrometer(FTIR),X-ray diffractometer(XRD),gel permeation chromatography(GPC)and hydrogen nuclear magnetic resonance spectrometer(1H-NMR)were used to characterize the structure of PAM-GSH and PAM-MSA mixtures,verified the rationality of mercapto-initiated polymerization of acrylamide in GSH and MSA,and discussed the mechanism of mercapto-initiated polymerization.Through further experimental design,PEDOT:PSS was introduced into PAM hydrogel to prepare purely physically-crosslinked PAM-MSA/PEDOT:PSS conductive hydrogel.Different from the PAM hydrogel prepared by chemical crosslinked method,the purely physically crosslinked PAM-MSA/PEDOT:PSS conductive hydrogel has a more uniform and dense three-dimensional network structure,which is more conducive to the transmission of ions as a conductive path.The electrical conductivity of the hydrogel can reach 4.45 S/m,the tensile strength is 248 kPa,the elongation at break is 213%,and the toughness reaches to 476 kJ/m3.The PAM-MSA/PEDOT:PSS conductive hydrogel is assembled into a strain sensor with flexible,stretchable,compressible and other characteristics,which can stably detect human motion signals and have other uses,and has a short response time(101 ms),high sensitivity(GF=5.49).The study shows that the prepared PAM-MSA/PEDOT:PSS conductive hydrogel material has potential applications in artificial intelligence,human motion monitoring,health monitoring,and flexible wearable devices.