Snap Fasteners for Micro Assembly

Single Crystal Silicon Latching Mechanisms (1992-1995)

Team Members

Karl F. Böhringer, Bruce R. Donald, Noel MacDonald, Rama Prasad (Cornell)


A snap fastener is a deformable device consisting of a pair of mating surfaces that "snap"' together during assembly. Because of the simple, linear assembly motion, snap fasteners have a wide range of applications in micro assembly tasks, e.g. for devices with multiple or layered components, or micro opto-mechanical plugs. At the micro scale, conventional types of fasteners like screws and hinges are unlikely to work due to present fabrication constraints and large friction forces. Micro snap fasteners also have great potential to be used in sensors with memory.

We have conducted a detailed theoretical analysis of design and function of micro snap fasteners, and describe the fabrication in single crystal silicon (SCS) technology. To verify the theoretically obtained design rules we conducted experiments with independent comb drive actuators which generate micro-Newton forces to actuate and engage the fasteners.

Figure 1: Engaged micro snap fastener: single latch design. Figure 2: Micro snap fastener: double latch design.
Figure 3: Comb drive actuator with micro snap fastener.

There exist efficient computational tools for analysis and simulation of snap fasteners which make it possible to automatically generate the appropriate design of a snap fastener given just the functional specification of the device. Combined with the highly automated VLSI fabrication process, this allows a virtually completely automated production, making snap fasteners one of the very few devices that can be fabricated automatically given only their functional specification.

Selected Publications

  • Rama Prasad, Karl F. Böhringer, Noel C. MacDonald, "Design, Fabrication, and Characterization of SCS Latching Snap Fasteners for Micro Assembly." ASME International Mechanical Engineering Congress and Exposition (IMECE), no. DSC-16A-1, San Francisco, California, November 12-17, 1995. Paper.

A complete list of our publications (many of them available online) can be found here.


  • ARPA under contract DABT 63-69-C-0019
  • NSF grant ECS-8619049
  • NSF IRI-8802390, IRI-9000532, IRI-9201699, and by a Presidential Young Investigator award to Bruce Donald, NSF/ARPA SGER IRI-9403903
  • Air Force Office of Sponsored Research, the Mathematical Sciences Institute, Intel Corporation, and AT&T Bell laboratories.

© Karl F. Böhringer, Department of Electrical Engineering, Box 352500, Seattle, WA 98195-2500, USA