The Use of Shape Memory Polymers for MEMS Assembly

The advantages of utilizing the polymeric shape memory effect for deterministic assembly of microscale objects are explored in this paper. Assembly of building blocks, referred to as inks, by transfer printing is performed using a polymeric stamp with reversible adhesion as a manipulator. The dynamic rigidity control of a shape memory polymer (SMP) stamp afforded by heating or cooling it across its glass transition temperature allows for a dramatic increase in adhesion during ink retrieval. Furthermore, the shape-fixing and recovery property of the SMP material enables substantial freedom in stamp design, such as more complex surface patterning and heterogeneous surface features, to further reduce adhesion during release, not otherwise available. The mechanics of the stamp adhesion, including the effect of the material's viscoelasticity and dynamic rigidity on performance, is discussed. Example structures, including a micro-motor structure with a movable rotor, are assembled in order to highlight the benefits afforded using the SMP material over existing alternatives.