Graphene lens shifts focus without a motor: autofocus shrinks to a membrane

Engineers at Queen Mary University of London have built a soft lens that changes its focal length under an electric field, with no motors or mechanical parts involved. The design relies on transparent stretchable electrodes made of graphene applied to an elastic substrate. The researchers compare the optics to a living eye and see it as a foundation for next-generation wearable electronics.

The key feature is that the actuator sits directly on the optical axis of the lens. The electric drive, made of transparent reduced graphene oxide (rGO), is integrated into the lens itself rather than being a separate bulky mechanism like in traditional cameras.

The device works through a dielectric elastomer actuator (DEA). It is a pre-stretched thin polymer membrane sandwiched between deformable electrodes. When voltage is applied, electrostatic forces compress the membrane, changing its curvature and therefore its focus.

The electrodes are made by spraying rGO directly onto the elastomer surface, with a layer thickness ranging from 50 to 80 nm. Adding more material cut surface resistance by tens of times, but transparency at a 550 nm wavelength dropped from roughly 42% to 17%. The team had to find a compromise between conductivity, stretchability, and light transmission.

For the prototype, they chose an electrode density that lets about 32% of light through. At an electric field strength of 50 V/µm, the membrane area changed by approximately 10%. With an elastic lens attached to the actuator, the focal length shifted from 30.1 mm to 36 mm.

For now, this is a lab prototype, and the researchers still need to improve electrode transparency. Still, the absence of motors and mechanics could lead to thinner, lighter, and quieter autofocus systems for cameras, glasses, AR/VR displays, miniature medical devices, and scientific optics.