This paper describes binding-sequence control in self-assembly of microparticle by changing interactive forces from the outside. We demonstrated a sequential self-assembly with two binding steps. At the 1st step, the microparticles start to bind to each other on their hydrophobic surfaces (surface A) in aqueous solution. By changing the pH of the solution, the particles subsequently connect on their hydrophilic surfaces (surface B) at the 2nd step. We confirmed that this sequential process increases the yield of the assembled structure, and concluded that pH control is effective to achieve a sequential self-assembly.

References :
Hiroaki Onoe, Kiyoshi Matsumoto, Isao Shimoyama, “Sequential Self-Assembly by Controlling Interactive Forces between Microparticles,” 17th IEEE International Conference on Micro Electro Mechanical Systems (MEMS '04), pp. 5-8, Maastricht, The Netherlands, Jan. 25-29, 2004. [Proceedings]

Hiroaki Onoe, Kiyoshi Matsumoto, Isao Shimoyama, “Three-Dimensional Micro-Self-Assembly using Hydrophobic Interaction Controlled by Self-Assembled Monolayers,” Journal of Microelectromechanical Systems, vol. 13, No. 4, pp. 603-611, 2004. [Paper]