Paper-Based Wearable Sensors for Humidity and VOC Detection

Acceptable indoor air quality is a concern for the comfort and health of humans, in which the 40–70% of relative humidity (RH) is comfortable for the human body and the existence of volatile organic compounds (VOCs) may be harmful for our health. Therefore, the development of wearable sensors that can monitor the RH and VOCs in real time is highly desired. In this work, a mixture of conductive carbon black and exfoliated graphene was dip-coated on filter paper to easily fabricate a paper-based flexible sensor, which can detect RH in the range of 33–95% and VOCs including methanol (MeOH), ethanol (EtOH), toluene (PhMe), dichloromethane (DCM), acetone, and petroleum ether (PE) with relatively short response time. The device can be used to monitor the indoor RH and human breath under various conditions. It also can work as a sensitive and quick-response alarm for the VOC exposure. Furthermore, this flexible sensor is disposable by ultrasonic treatment without producing hazardous residues, thus considered as an environment-friendly electronic. This versatile and green flexible electronic device may find applications in wearable air monitoring devices and health care.