Study On Aerosol Jet Printing Of Flexible Strain Sensors And Microstructure Regulation

With the advancement of technology and people’s increasing demands for quality of life,flexible electronics technology has emerged as a new technology that enables electronic devices to have flexibility,expanding the scope of electronic device applications.Flexible strain sensors,as a type of flexible electronic device,are widely used in human-machine interaction and health monitoring.Although there have been many research achievements on flexible strain sensors reported,designing flexible strain sensors at multiple scales remains a major challenge.In this study,we employed aerosol jet printing technology,one of the electronic printing technologies,to fabricate highly sensitive flexible strain sensors by controlling the microscale reaction field during the printing process and adjusting the microstructure of material stacking.An improved polyol method was utilized to synthesize silver-based functional materials by introducing chloride ions and bromide ions as ionic assistants for synergistic regulation of the reaction process.The ink suitable for aerosol jet printing technology was formulated by selecting deionized water as the solvent.As the aerosol jet printing technology transports aerosol droplets through the air and focuses them into a jet at the nozzle,different deposition behaviors occur when micro-droplets are deposited on substrates with different surface properties.By selecting substrates with different surface properties,changing the deposition temperature,and adjusting the evaporation rate of droplet solvents,the temperature gradient between the top and bottom of the droplet creates Marangoni flow and capillary flow within the droplet,inducing different migration phenomena of solutes and selfassembly of solutes,thereby regulating the microstructure of stacked materials.This also proves that the surface properties of the substrate play a critical role in the stacking structure of solutes.Under the printing temperature of 75℃,a super white glass substrate was selected to induce the coffee ring effect and construct a tightly overlapped three-dimensional conductive network for the preparation of flexible strain sensors.The optimal sensitivity value of the prepared sensor was obtained when the number of printed layers was 15.At a stretching rate of 25%,the sensitivity coefficient was 23.18.Stable testing for 1000 cycles proved its good stability.By integrating the sensor into an electrical circuit,it can be used to control the working state of components in the circuit.To further explore its application scenarios,the sensor was fixed on the finger joints,forearms,and knees,exhibiting significant responses to joint bending.When fixed on the throat,it could detect slight skin deformation during speech.This work also demonstrates that droplet-based efficient aerosol jet printing technology has great potential in developing advanced flexible devices for wearable electronic applications at multiple scales.