Nickel oxide-nickel heterostructures point to cheaper, efficient wearable temperature sensors

While today’s wearable temperature sensors convey human body temperatures, most remain expensive to produce and low efficiency. One proposed solution has been to repurpose low-cost, nickel-based devices.

Zhang et al. present a type of wearable temperature sensor that draws on metal-semiconductor-metal self-gated devices and use nickel oxide/nickel (NiO/Ni) heterostructures. Assembling self-gated devices with a relatively straightforward and controllable in situ oxidation method, the group produced a flexible sensor array to measure the spatially resolved temperature distribution.

“In our work, nickle framework was used as the precursor of the NiO/Ni heterostructure temperature sensor, which is common and widely used with low price,” said author Jixin Zhu. “In addition, the fabrication method of our work is facile and low-cost, suitable for scale production.”

The device is able to measure temperatures of the surface of the human body and inanimate objects. It demonstrates efficient charge transportation, excellent thermal conductivity at 3.74 watts per meter-kelvin and high thermal diffusivity at 9.39 square millimeters per second.

It covered a high sensitivity, -5.04% per degree Celsius, a wide range of applicable temperatures, from -15 to 80 degrees Celsius, and remained stable for more than three months.

“We have tried many kinds of materials and many forms of devices based on negative temperature coefficient materials, and surprisingly, we found the fabrication of high-performance temperature sensors can be achieved by growing nickel oxide on a nickel framework conductor,” Zhu said. “This vertical charge transport results in low resistance despite the high resistivity of nickel oxide.”

The group looks to find ways to explore similar phenomena in other heterostructures and create temperature sensor arrays with larger areas and finer resolution.

Source: “Robust self-gated-carriers enabling highly sensitive wearable temperature sensors,” by Hongjian Zhang, Kui Xu, Yufei Lu, Haodong Liu, Wenqi Han, Yang Zhao, Ruizi Li, Zhentao Nie, Feng Xu, Wei Huang, and Jixin Zhu, Applied Physics Reviews (2021). The article can be accessed at https://doi.org/10.1063/5.0059204 .