Fast response humidity sensor based on hyperbranched zwitterionic polymer for respiratory monitoring and non-contact human machine interface

Abstract

Non-contact humidity sensing is a prospective method for gathering biomedical information and realizing the non-screen-contact human–machine interaction. However, humidity sensors with both fast response and recovery are still considered a significant challenge. This study proposes to develop a humidity sensor based on hyperbranched zwitterionic polymer (PTS). The sensors are featured with fast response and recovery (3 s/3 s) as well as outstanding repeatability in the range of 11%-98% RH. The excellent sensing performance of PTS benefits from the rational regulation of molecular interactions. LiCl is then employed to dope the PTS to fabricate PTS/LiCl composite sensitive materials. The introduction of conductive ions further improves the sensing performance, and the modified humidity sensor exhibits an ultrafast response (0.2 s). The PTS/LiCl sensors demonstrate robust long-term stability and good anti-interference capability. Sensors are also developed into masks for respiratory status monitoring. A gesture monitoring keyboard is constructed by integrating sensor array panels with control circuits to recognize non-contact gestures. The results prove that hyperbranched zwitterionic polymers offer a promising perspective as humidity sensing materials for the application of biomedical monitoring and human machine interfaces (HMI).