CAREER: Electrochemical Dynamic Midinfrared Metasurface for Ultra-Low Power Wearable Thermoregulation

Thermal comfort is one of the most essential fundamental needs for human health and productivity. The seasonality of cardiovascular diseases and influenza demonstrates the importance of stabilizing our thermal environments. However, because of its necessity, indoor temperature control is also associated with enormous energy consumption and carbon emission.

This proposed work aims to break the health-energy dilemma by developing a wearable radiative thermoregulation device that can localize heat management around the human body. Like a chameleon that can change its visible color, the wearable device can act like a second skin that changes the level of radiative heat loss into the environment to offset the adverse ambient temperature change.

The thermal radiation is tuned by an electrochemical reaction that uses less than 1 V as operation voltage. This working principle is similar to a battery but with the focus on its mid-infrared optical property change. Like a battery that can maintain its state of charge for a long time, the device can also maintain its heating/cooling state with ultralow energy consumption, which is orders of magnitude more efficient than traditional active devices such as electric blankets.

To promote diversity, equity, and inclusion, the project will organize the annual workshop series called LITE (Light, Infrared, and Thermal Energy) for underrepresented students by collaborating with the Step Up to STEM program at North Carolina School of Science and Mathematics. The workshop series aims to inspire high schoolers’ interest in photonics, thermal science, and general STEM fields by providing introductory lectures and immersive hands-on experiments such as thermal vision VR goggle DIY sessions.

In photonic technical terms, the device adopts a metal-insulator-metal configuration and the working principle of a midinfrared metamaterial perfect absorber. It uses electrochromic conjugated polymer, such as polyaniline, as the active material. By electrochemically biasing the polymer, its carrier density, plasmon frequency, and permittivity are tuned dynamically and reversibly, thus varying the device state between a metamaterial absorber and a simple metallic reflector, which is equivalent to emissivity tuning based on the Kirchhoff’s law of thermal radiation and the zero transmittance.

This project will involve multiscale and multidisciplinary study in materials science, photonics, heat transfer, and wearable device engineering. Specifically, the project will develop the correlation among polymer synthesis condition, structural characterization, charge transport measurement, mid-infrared permittivity, metamaterial absorber designs, and heat transfer measurement.

The proposed research will scale up the adaptive metamaterial absorber and implement Kirigami paper cutting technique to provide stretchability, breathability, and conformal deformability from 2D thin film to 3D shapes for wearable applications. The wearable metasurface thermoregulation will further advance the emerging field of multimodal and multispectral light and heat management for the health-energy nexus.

The in-depth study of electrochemically active polymers will also become an enabler for adaptive optical metasurfaces, sustainable energy science, and personalized preventive medicine.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.