Our eyes can switch focus almost instantly, moving from words on a page to something across the room without us even thinking about it.
Recreating this simple-looking ability in cameras and other optical devices, however, usually requires lenses, motors and other moving parts.
Researchers at Queen Mary University of London have now developed a soft lens that takes a different approach.
Using a transparent material made with graphene, the lens can change its focus electronically without relying on bulky mechanical systems.
The research, led by Professor James Busfield, was published in Advanced Functional Materials. The technology could eventually be useful in smart glasses, autofocus cameras, virtual and augmented reality headsets, medical imaging equipment and scientific instruments.
Traditional cameras and microscopes usually focus by physically moving rigid lenses. While effective, these mechanical systems can add weight, size, noise and complexity.
The new prototype behaves more like the human eye. Instead of moving the entire lens forward or backward, an electrical signal gently changes the shape of a soft lens. Changing its shape changes its focal distance, allowing objects at different distances to come into focus.
One of the biggest challenges in creating such lenses has been the electrodes needed to control them.
Electrically driven soft lenses require flexible electrodes, but conventional electrode materials often block light. Engineers therefore have to position them around the edges of a lens rather than directly underneath it. This limits how small and simple the device can become.
The researchers addressed this problem using reduced graphene oxide, a graphene-based material that can conduct electricity while remaining relatively transparent.
They created extremely thin electrodes and placed them directly on the soft actuator beneath the lens. When a small electric field is applied, the actuator expands and stretches the lens membrane, changing the lens’s shape and therefore its focus.
The researchers carefully controlled how much graphene-based material was deposited onto the membrane. Too much could reduce transparency, while too little would limit electrical performance. By finding a suitable balance, they produced a compact prototype capable of focusing across a range of distances.
The technology is still experimental, and researchers say further improvements are needed, particularly to make the electrodes more transparent and improve overall performance.
But the approach could offer important advantages over conventional focusing systems. Soft electrically active materials can behave somewhat like artificial muscles, smoothly changing shape when they receive an electrical signal. They can operate without the motors and gears normally required to move lenses.
Combined with graphene’s useful electrical properties, this could allow engineers to create optical systems that are smaller, lighter and quieter.
The researchers also say the lens can be made using relatively simple manufacturing techniques and inexpensive materials.
If the technology can be further developed, future cameras, wearable displays and miniature medical devices may be able to focus more like our eyes—by changing shape rather than moving rigid pieces of glass.
