Wearable gas sensor able to monitor environmental and human health on its way to commercialization
Researchers at Penn State and Northeastern University believe that a highly sensitive, wearable gas sensor for monitoring environmental and human health might soon be commercially available. The sensor device is an upgradation of the existing wearable sensors as it uses a self-heating mechanism with improved sensitivity. It facilitates quick recovery and reusability of the device. Other devices of this type run on an external heater. Additionally, other wearable sensors need an expensive and time-consuming lithography procedure under cleanroom conditions.
Huanyu Cheng, Assistant Professor, Engineering Science & Mechanics and Materials Science & Engineering, Penn State, says that people prefer to use nanomaterials for sensing because their large surface-to-volume gives them higher sensitivity. The problem, according to Cheng, is that the nanomaterial is not something that can easily be hooked to with wires to receive the signal, raising the need for interdigitated electrodes, which are like digits.
Cheng and his team utilized a laser for patterning a highly porous single line of nanomaterial similar to graphene for sensors that can detect gas, biomolecules, and in the future, might also be able to detect chemicals. In the non-sensing part of the device platform, the team created a series of serpentine lines that were coated with silver. Upon applying an electrical current to the silver, the gas sensing region heats up owing to a marginally higher electrical resistance, rendering a separate heater unnecessary. The serpentine lines enable the device to stretch, like springs, to adjust to the flexibility of wearable sensor devices.
The nanomaterials used for this purpose are reduced graphene oxide and molybdenum disulfide, or a blend of the two, or a metal oxide composite containing a core of zinc oxide and a shell of copper oxide, representing the two classes of broadly used gas sensor materials, i.e., low-dimensional and metal oxide nanomaterials. Cheng says that with a CO2 laser, commonly found in machine shops, they can seamlessly build multiple sensors on the platform, and they plan to make tens to a hundred sensors, each of which reacts to a different molecule, such as an electronic nose, for decoding multiple components in a complex mixture.