Automated Manipulation of Miniature Objects Underwater Using Air Capillary Bridges—Pick-and-Place, Surface Cleaning and Underwater Origami

Various insects can entrap and stabilize air plastrons and bubbles underwater. When these bubbles interact with surfaces underwater they create air capillary bridges that de-wet surfaces and even allow underwater reversible adhesion. In this study, a robotic arm with an interchangeable 3D- printed bubble-stabilizing unit is used to create air capillary bridges underwater for manipulation of small objects. Particles of various sizes and shapes, thin sheets and substrates of diverse surface tensions, from hydrophilic to superhydrophobic, can be lifted, transported, placed and oriented using one or two-dimensional arrays of bubbles. Underwater adhesion, derived from the air capillary bridges, is quantified depending on the number, arrangement and size of bubbles, and the contact angle of the surface. This includes a variety of commercially available materials and chemically modified surfaces. Overall, it is possible to manipulate millimeter to sub-millimeter scale objects underwater. This includes cleaning submerged surfaces from colloids and arbitrary contaminations, folding thin sheets to create three-dimensional structures and precise placement and alignment of objects of various geometries. The robotic underwater manipulator can be used for automation and control in cell culture experiments, lab-on-chip devices and manipulation of objects underwater. It offers the ability to control transport and release of small objects without the need for chemical adhesives, suction based adhesion, anchoring devices or grabbers.