Disposable, strain-insensitive, and room-temperature-operated flexible humidity and VOC sensor with enhanced sensitivity and selectivity through interface control

As people are paying more attention to the health and comfort of the indoor environment, the sensors detecting the relative humidity (RH) and volatile organic compounds (VOCs) have attracted widely research interests. However, how to improve the sensitivity and selectivity remains a challenge, especially for flexible sensors working at room temperature (around 25 celcius). In this work, the controlling of solid-gas interface was found to be able to enhance the sensitivity and the manipulation of solid-solid interface increased the selectivity of the sensor for VOC detection. The flexible sensor based on electrospinning cellulose (EC) show high sensitivity for humidity detection due to its large solid-gas interface, which can be used for real-time monitoring of human breathing and speech recognition, simultaneously, it can also detect a variety of VOCs. By introducing silver nanowires (AgNWs) to establish solid-solid interface between silver and expanded graphite (EG), the selectivity of the sensor for VOCs detection was improved, which shown higher sensitivity for EtOH with faster response/recovery time, as well as long-term cycle stability and bending insensitivity. Furthermore, the sensor also can be decomposed by burning, offering a sustainable disposal method. This versatile, low-cost and environmentally friendly flexible electronic device may be used for wearable air monitoring and environmental controlling.