Two-dimensional micro-self-assembly using the surface tension of water

Several self-assembling microstructures have been fabricated, and approximately 100 units floating on the surface of water were self-assembled two-dimensionally. The basic assembly units are 400 μm large, and consist of both polyimide and polysilicon thin films. Surface tension was used in this system as the bonding force. The surface tension is the local interaction between the units, and is dominant in the microscale. Each unit was bonded selectively by employing the following characteristics of the surface tension: 1) objects located at equal heights are attracted to each other, 2) large attractive forces act on sharp parts, and 3) objects located at different heights are mutually repulsed. The curling-up property of the thin films was used to obtain the different heights. Self-assembling behaviour was also predicted by using a rate equation