Arrays of lenses smaller than a millimeter across could lead to biological and chemical sensors that behave like an insect’s compound eye, according to the authors of an article in the journal Nature.

Each of the lenses is a drop of water that focuses by bulging up or receding through a small hole in a polycarbonate film as a surrounding hydrogel ring expands and contracts.

So far, the researchers have used hydrogels that change shape in response to changes in pH or temperature, but they plan to make versions responsive to electricity or specific antigens for diseases.

If exposed to these antigens, for example, the change in the focal length of the lens would give a clear optical signal, making it possible to detect a disease. And an array of such sensors, which would look and react to stimuli like an insect’s compound eye, could detect different chemicals or diseases. – By Kevin Bullis