MICRO ASSEMBLY
Definition: Building a variety of mechanical MEMS structures via 3D assembly.
Conventional MEMS thought strives for monolithic integration of all MEMS components, driving towards the small number of markets demanding huge quantities of extremely cheap components. We believe a need exists to build smaller quantities of higher value-added hetrogeneous systems via assembly.
Some materials systems are hard to integrate monolithically, leading to dubious payback of the non-recurring engineering cost of perfecting the monolithic integration. Sometimes, high performance system requirements necessitate using state of the art components, which may be easier to procure and assemble as individual components, rather than worrying about wafer-level integration. Sometimes, only a few systems are needed. A prototype MEMS assembly robot is a perfect example of a low volume system better assembled than monolithically integrated.
Our MEMS assembly technology relies on the precision dimensions of MEMS to define self-aligning snap connectors, which can be mated with a relatively low precision assembly robot. This robot is driven from automatically generated scripts which pick and place the parts. The parts are made on a SOI (Silicon On Insulator) wafer, and are tethered in place by breakable tethers, so the parts stay put during the release phase, and thus can be located automatically. Hand assembly under the microscope is also possible for delicate situations not yet automated.
Assembled gear on a 100 micron diameter tungsten wire. This is driven from the stepping rack meshing below the gear, which is moved laterally by thermally actuated stepping fingers. The stepping fingers engage the small teeth just visible along the edge of the rack, and can step with relatively high force. This is how the gear assembly at the top of this page is driven.
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Assembled micromotor. The rotating piece is just visible under the cap, which serves to hold it in place. The thermally-actuated drive is capable of bidirectional motion. The hole in the center allows a probe wire (typically 100 micron diameter) to be inserted and rotated. Click for .WMV video (~1.5MB).
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Optical closeup of the completed mini-SEM lens assembly. Typical precision of these lens elements is within 1/2 degree of vertical without any glue at the base, but becomes much better when the lens elements are glued in after assembly. Such glued joints have been tested to withstand well over 15000 G's - the silicon parts break before the glued joints. This prototype supported several hundred volts across the lens elements, limited by substrate breakdown. A different substrate would allow thousands of volts between lens elements. |
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This impressive little video shows an assembled MEMS rotator assembling another part that it previously picked up. Click for .AVI video (~2.5MB) |
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Built as a test of the sturdiness of our snap connectors, this structure cantilevered 21 components up off the substrate, out over the edge, and down. No glue was used, and the structure was sturdy enough to be gently handled during transfer to the electron microscope which took these images. |
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We built numerous grippers and tweezers — this shows a microgripper mounted to plug into the fine positioner of one of Zyvex Instruments’ nanoprobers. Click on the image for a magnified view of the gripper. |
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