Fabrication of a cylindrical display by patterned assembly

We demonstrate the patterned assembly of integrated semiconductor devices onto planar, flexible, and curved substrates on the basis of capillary interactions involving liquid solder. The substrates presented patterned, solder-coated areas that acted both as receptors for the components of the device during its assembly and as electrical connections during its operation. The components were suspended in water and agitated gently. Minimization of the free energy of the solder-water interface provided the driving force for the assembly. One hundred and thirteen GaAlAs light-emitting diodes with a chip size of 280 micrometers were fabricated into a prototype cylindrical display. It was also possible to assemble 1500 silicon cubes, on an area of 5 square centimeters, in less than 3 minutes, with a defect rate of similar to2%.