Force and humidity dual sensors fabricated by laser writing on polyimide/paper bilayer structure for pulse and respiration monitoring

Paper-based sensing technology has attracted much attention due to its light weight, low cost, ease of fabrication, and many other advantages. Here we combine paper-based sensing technology with a direct laser writing method to design and fabricate a simple and wearable healthcare sensor based on polyimide (PI)/paper bilayer structure. With assistance of infrared spectroscopy, thermogravimetric analysis, Raman spectroscopy, scanning electron microscopy and coupled electrical-mechanical testing, the effect of material processing temperature on the sensing characteristics of the PI/paper bilayer film was studied. The PI/paper bilayer film-based sensors have been successfully demonstrated for their use in monitoring pulsing and respiration activities, and in working as dual sensors for simultaneously detecting force and humidity stimuli. The differential response of PI and paper to different chemical and physical stimuli would make the PI/paper bilayer film a versatile platform for developing multi-functional and multi-modal sensors. Paper-based sensing technology was combined with direct laser writing for designing and fabricating low-cost wearable multifunctional sensors.