New device advances possibilities for displays and biosensing

By Peter Murphy

Peter Q. Liu, associate professor in the Department of Electrical Engineering, is corresponding author of the study “Electrically Reconfigurable Liquid Metal Nanophotonic Platform for Color Display and Imaging,” recently published in Advanced Materials, that details the new devices that could enhance everyday devices and critical processes.

“We invented a new type of electrically reconfigurable nanophotonic device which employs gallium-based room-temperature liquid metals to achieve structural transformability and reconfigurability,” Liu says. “Such liquid-metal-based reconfigurable nanophotonic devices may find a wide range of applications, such as color displays, tunable optical filters, biosensing and bioimaging.”

Gallium-based room-temperature liquid metals give the device its ability to seamlessly transform — a key advantage over conventional solid metals used in various devices. Many of the items with a tunable or reconfigurable display that we use today — like TV and monitor screens or some smartphones and tablets — use liquid crystals, which has shortcomings. Liquid crystal displays depend on backlights and require constant power to display images, consuming more energy than necessary. It is also challenging to use liquid crystals for high-performance reflective displays for devices encountering strong ambient light, like bright sunlight. The new device developed by Liu and his team offers a viable path towards high-performance reflective displays that address the limitations of other materials used for similar purposes.

The nanophotonic device, a small optical device, uses a hybrid resonator structure to function. The first piece of the structure is liquid metal, contained in a microfluidic system that allows the researchers to control the liquid metal’s movement. The second piece of the structure consists of gold nanopatches. Gold nanopatches are employed as the top structure of the hybrid resonators because gold has favorable optical response and excellent stability. The layer of liquid metal acts as a moving ground plane — like a moving mirror — that can drastically modify how light interacts with the gold nanopatches. When voltage is applied to the system, it triggers an electrochemical wetting effect, causing the liquid metal to shift. This shift causes drastic and reversible changes to the device, which translate to visible color changes.

The spectral responses — the color changes — of liquid-metal-based nanophotonic resonators are highly sensitive to other microscopic or nanoscale objects like nanoparticles or nanometric thin films. These resonators can detect and reveal objects that are otherwise unobservable. According to Liu, these devices could have an array of applications like color displays, tunable optical filters, biosensing and bioimaging.

“We believe this work has blazed a new trail in tunable photonics research and will likely simulate further development of liquid-metal-based photonic devices and systems for various applications by the research community, and eventually lead to technology adoption by the industry,” Liu says.

Additional co-authors include Md Abdul Kaium Kahn, a PhD student in electrical engineering and UB Presidential Fellow; Shoaib Vasini, another UB PhD student in electrical engineering; and Ralu Divan, a collaborator at the Argonne National Laboratory.

This research is funded by the National Cancer Institute and National Science Foundation.