Abstract This study presents a contactless, light‐driven method for manipulating unicellular and filamentous cyanobacteria. While these microorganisms can cause environmental issues through blooms and toxin production, they also hold promise for sustainable biotechnology. The approach relies on diffusioosmotic flow generated by irradiating a solution containing a photoresponsive azobenzene surfactant. Upon exposure to specific wavelengths, the surfactant reversibly switches between a hydrophobic trans‐state and a hydrophilic cis‐state, creating concentration gradients at the solid/liquid interface. These gradients establish an osmotic pressure difference, driving flow along the surface. Bacteria are passively transported and accumulate in the illuminated area, and by moving the light spot, they can be relocated with precision. The reversible photo‐isomerization, combined with adjustable light intensity and wavelength, enables precise control over bacterial speed, direction, and trapping location. This method allows versatile, contactless manipulation of single cells or ensembles, supporting operations such as trapping, removal, and translation. All actions are performed without physical contact and with high spatiotemporal control, offering a noninvasive approach for advanced microbial handling and demonstrating the potential of light‐controlled microfluidic systems for both research and biotechnological applications.
Umlandt et al. (Wed,) studied this question.
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