Linear bi-layer humidity sensor with tunable response using combinations of molybdenum carbide with polymers

- Liquid mechanical exfoliation of Mo2C to achieve 2D flakes and particles.
- Combination of transition metal carbide with polymers to enhance humidity sensing properties.
- Bi-layered structure of active region to achieve linear and stable response.
- Detailed investigation of working principle and sensing mechanism.
- Fast sensor response and recovery times.

A high performance humidity sensor for environmental and health monitoring has been fabricated using various combinations of molybdenum carbide (Mo2C) with polyacrylamide (PAM) and polyvinyl alcohol (PVA). The humidity sensing properties of pure Mo2C were compared with those of its composites with PAM and PVA. The response curves and working principle were investigated and novel bi-layered sensors were then fabricated to achieve highly linear and stable response for a wide range of humidity sensing (0% RH to 90% RH). The sensors having a bi-layer combination of Mo2C with PAM give a linear response with a sensitivity of 775 Ω/%RH and excellent repeatability. The working mechanism of the sensors allow them to be used with frequency response conversion read-out circuits and the results ascertain their linear and stable behavior. The response-time and recovery-time of the sensors were measured that gave average values of ∼1 s and ∼2.5 s respectively for the composites and ∼1.8 s and 2.3 s for the bi-layer configuration. The sensors are aimed to replace low performance complex and expensive sensors in the market for environmental and health monitoring applications.