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From Velcro to solar cells, many technological innovations have been inspired by nature. In medical diagnostics, researchers also draw inspiration from biological principles. A research team from the University of Freiburg and the INM—Leibniz Institute for New Materials in Saarbrücken has developed testing methods in which simple LEDs could replace complex mechanical pumps. These OptoAssays not only mimic the behavior of biological cells but also use their genetic programming.

A SARS-CoV-2 rapid test indicates whether a specific protein of the coronavirus is present in the sample liquid, the reagent, or not. A pregnancy test works in a similar way. Here, the presence of the hormone hCG causes the test line to color.

In both cases, a lateral flow assay is used, a test in which the sideways flow of the reagent leads to a result being displayed. This single unidirectional movement of the liquid on the paper is created purely by capillary forces, without any mechanical or electrical assistance.

For more complex tests, this detection method is not suitable. Here, assays are required that allow for bidirectional control of liquids, meaning the transport into and out of the test system. Unfortunately, these multistep assays rely on expensive and wear-prone pumps.

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