Painting sustainable wearables: facile and economical all-recycled dual temperature-motion wearable sensor for monitoring of human temperature and joint movements

Abstract

World is seeing rapid increase in smart wearable electronic devices and gadgets especially for personal healthcare and activity monitoring. It is estimated that e-waste generation will reach 75 million tons by 2030 which is posing life-threatening complication by polluting environment. To build sustainable and green world; facile, economical, multi-functional, biodegradable, and recyclable wearable sensors have great potential in human health and activity monitoring in developing countries, especially in rural areas due to budgetary constraints and geographic inaccessibility. This paper presents a facile, and economical, all-recycled dual temperature-motion (ARDTM) wearable sensor patch to monitor human body temperature and joint movements. The proposed ARDTM wearable sensor is fabricated by recycling/re-using e-waste (dry cells) to get graphite and paper. Paper is employed as the substrate due to its low-cost, abundance, flexibility, biocompatibility, biodegradability, and disposability. The graphite extracted from the discarded dry cells is mixed with gel pen ink to make conductive graphite paste. Resistive temperature sensor and capacitive motion sensor are brush painted on sticky-note paper using conductive graphite paste. The sensors are integrated together to monitor body movements and temperature simultaneously in a compact and decoupled manner. To demonstrate the isolation of both sensors, the response of the dual sensor patch is examined simultaneously for body temperature and wrist movement. The temperature sensor is characterized by measuring change in resistance over a temperature range of 25 °C – 65 °C in addition to body temperature and it demonstrated a sensitivity of ∼335 Ω/°C. For monitoring human body movements, the capacitive response of motion sensors is tested on several body parts especially the wrist, knee, elbow, and finger. The ARDTM wearable sensor is facile, low-cost, multipurpose, biodegradable, compact and can be used to simultaneously monitor human activities and health. Our approach realized multi-purpose wearable sensor by recycling/re-using paper and e-waste, which provides a way forward for the sustainable and green development of wearable sensors by mitigation of e-waste.