MEMS-based humidity sensor based on thiol-coated gold nanoparticles

A MEMS-based humidity sensor is proposed comprising thiol-coated gold nanoparticles (AuNPs) deposited on a glass substrate with aluminum interdigitated electrodes (IDEs). In the proposed device, the humidity is measured by monitoring the change in the device resistance as the water molecules are absorbed by the AuNPs. A highly sensitive sensing performance is obtained as a result of the large surface area of the AuNPs and the hydrophilic nature of the thiol coating. The experimental results show that the sensor has a time response of 10 s when the humidity is changed abruptly from 30%R.H. to 80%R.H. and a recovery time of 5 s when the humidity is restored to 30%R.H. In addition, it is shown that the sensor has a sensitivity of 2.83 kΩ/%R.H. over the humidity range of 20 ~ 90%R.H. Finally, the sensor is shown to have good reliability (i.e., ±1.2%R.H.) over an extended period of 72 h.