London Light researchers at King’s have proposed a new design for future microscopic vehicles powered by light.
Published in Optics Letters the team of researchers, including Dr Jack Kingsley-Smith and Dr Yanhui Hu, designed a 2D metasurface that is capable of controlling and redirecting light that passes through it. In doing so, the metasurface generates an optical force as the transmitted light’s momentum is shifted and redirected. If the metasurface is placed on top of a body, a metavehicle is formed and the metasurface’s optical force becomes the driving mechanism. Metavehicles have already been used experimentally to move cells and yeast particles significant distances, and are envisaged for the precise movement of microscale bodies and complement bottom-up fabrication techniques.
This new work implements a phase-gradient metasurface to achieve total control of the metavehicle’s velocity and heading, allowing the vehicle to drive backwards, forwards, and turn corners. A laser beam is directed at the metavehicle and the direction of travel is determined by the polarisation of the incident light. Therefore changing the metavehicle’s direction can be as simple as rotating a polariser. The use of a phase-gradient metasurface increases the range of optical forces that can be generated and also improves efficiency.
“Previous metavehicle designs provided a steering wheel and a range of forward gears, so to speak. The advantage of our design is that we are also providing a range of reverse gears; something that was not achievable with previous designs. We hope that this takes us one step closer to realising exciting new technologies that exploit these metavehicles.”
– Dr Jack Kingsley-Smith
Reversible lateral optical force on phase-gradient metasurfaces for full control of metavehicles’ – Optical Lettters 48, (2023)
Dr Jack Kingsley-Smith and Dr Yanhui Hu are members of the Photonics & Nanotechnology Group based in the Department of Physics at King’s College London