Researchers at A*STAR have designed a low-cost, stable and ultrafast graphene oxide-based responsive humidity sensor that is said to be easy to manufacture, overcoming the challenge of producing a simple, fast and highly sensitive version. The ability to monitor and control humidity levels using accurate and reliable sensors is essential for efficient manufacturing and storage practices as well as everyday life.
Unlike most humidity sensors, which are electronic and require a power supply, GO-based colorimetric sensors respond to humidity levels by changing color that can be easily observed. For greater accuracy, the change in color can be quantitatively measured by analyzing the reflection spectra of the sensor. Because the GO sensor operates at the atomic level, it can rapidly respond to moisture changes.
Exploiting the atomic properties of GOs can only occur if films of uniform thickness can be fabricated; thickness influences the response time and uniformity determines the quality of the sensor. The research team overcame this challenge by using a process, in which a substrate is dipped in and out of a solution at a constant speed. They optimized the solution viscosity, substrate-surface treatment and dip-coating conditions; This showed that it is possible to control the thickness of uniform films of GO with a process that is scalable and also generates zero waste.
The low-cost, non-toxicity and rapid response of GO sensors make are said to make them ideal as disposable sensors. They can be incorporated into food packaging, where humidity levels need to be strictly controlled for storage, for medical instrumentation and semiconducting device manufacturing and storage, as well as environmental monitoring. Their disposal also has no environmental impact.