In-place manufacturing method improves graphene foam gas sensor performance and production time

(nanowork news) When used as wearable medical devices, stretchy, flexible gas sensors can identify health conditions and problems by detecting oxygen and carbon dioxide levels in breath and sweat. It also helps monitor air quality in indoor or outdoor environments by detecting gases, biomolecules and chemicals. However, manufacturing devices made using nanomaterials can be challenging.

Researchers at Penn State University recently stepped up the manufacturing process for gas sensors. there A laser-assisted manufacturing approach that improves on drop-casting, an earlier method of dropping materials one-by-one onto a substrate using a pipette (“Wearable Gas Sensors for Health and Environmental Monitoring”).they the result Journal of Chemical Engineering (“In situ laser-assisted synthesis and patterning of graphene foam composites as flexible gas-sensing platforms”). A graphic representation of a laser-induced graphene foam gas sensor during fabrication. The light beam represents a laser that imprints nanomaterials into graphene foam substrates that are used to detect gases in air and sweat. (Image: Chen Group)

“Drop casting requires that each part of the sensor be synthesized separately and then integrated, which is logistically difficult, time-consuming and expensive,” said a memorial associate professor of engineering sciences and mechanics at the Pennsylvania State Institute of Technology. “In situ methods allow materials to be synthesized directly in one place, and the laser speeds up the process.”

In this process, a laser engraves nanomaterials directly onto a porous graphene foam substrate. The base material allows the sensor to be stretchy and flexible when applied to skin or objects.

According to Cheng, this approach opens up opportunities to use different precursors or nanomaterials and mix them in different ratios and ingredients. Previously, researchers used graphene oxide and molybdenum disulfide to create sensors. With the new method, the researchers tested four additional classes of materials, including transition metal dichalcogenides, metal oxides, noble metal-doped metal oxides, and composite metal oxides.

“Certain nanomaterials allow us to sense different biomarkers and gases, so having access to different materials is very important,” Cheng said. “For example, typically one nanomaterial he can only detect one target gas molecule. Having multiple options available means that more molecules can potentially be detected, which improves sensing capabilities.”

Using some nanomaterials, the researchers created an array of several small sensors arranged side by side. The array’s capabilities are comparable to the human nose, Cheng said.

“The nose has evolved to sense millions of odors using millions of cells,” Chen said. “Similarly, each sensor can detect different chemicals or particles.”

The new sensor design has allowed researchers to eliminate the need for a separate heat source, further reducing the complexity of device fabrication. In the new design, the gas-sensitive nanomaterials are integrated into a single line of porous graphene foam compared to the old design where the nanomaterials filled the gaps between the electrodes. The single-line resistance of porous graphene foam induces Joule heating for self-heating.

The result is a sophisticated sensor that has several uses, such as monitoring rapid rises in gas, such as on industrial sites, or gas accumulation over time, such as in cases of pollution, to alert users.

In the future, researchers plan to improve the sensor’s capabilities by programming nanomaterial composites to target specific gases or discriminate multiple gas species in complex mixtures. I’m here.