New fabrication process enables inexpensive production of complex, highly-articulated mechanical devices at the millimeter scale

Harvard University Office of Technology Development
posted on 08/18/2011

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MARKETS ADDRESSED:
The invented monolithic fabrication process enables low-cost production of complex, highly-articulated mechanical devices and functional machine components at the millimeter-scale – a capability not achievable using conventional manufacturing methods.

The fabrication of functional mechanical devices on the millimeter scale is a critical capability in fields such as autonomous microrobots and micromanipulation devices, and is important in the manufacture active components for technologies such as optical switches and smart antennas. However, available manufacturing technologies in MEMS and conventional machining lack the versatility, precision, and cost-efficiency to produce large quantities of functional devices on this scale. The present invention addresses this need through a series of process innovations which enable the monolithic fabrication of functional, three-dimensional mechanisms from a superplanar stack of precisely patterned material layers. This technology has direct applications to the mass production of autonomous robots, including service and hobby robots, and the manufacture of micromanipulation devices and other articulated millimeter-scale machines.

INNOVATIONS & ADVANTAGES:
Unlike bulk fabrication methods used in MEMS and conventional machining, the invented process allows the use of a wide variety of materials, including alloyed metals, polymers, and carbon fiber sheets, to create complicated kinematic linkages, support structures, and assembly-assist features on a single millimeter–scale manufacturing layup. This process also affords the integration of full subcomponents such as motors, ICs, and batteries into devices during the fabrication process. The invented process employs low-cost, low-power operations such as laser micromachining, press lamination, and origami-inspired folding techniques to greatly reduce assembly expense and increase process scalability.

The fabrication of the “Monolithic Bee” robot demonstrates the utility and novelty of the invented process. Fabrication starts with the laser micromachining of several material layers, ranging from structural carbon fiber sheet layers to flexible polyimide layers joint to create foldable joints (Figure 1). Laser micromachining creates patterns necessary for mechanical coupling, the release of rigid bodies comprising mechanical linkages, and the removal sacrificial material. Two piezoelectric transducer (PZT) plates used for device actuation are seen at the bottom of the image Figure 1.

Figure 1. Fifteen micromachined material layers used in the Monolithic Bee robot

After the initial micromachining, the material layers are aligned for press lamination using dowel pins and assembly-assist features cut into the layers. Micromachining and lamination operations can be performed several times on layups containing subsets of the device’s layers. After the insertion of the discrete PZT subcomponents into the layups, the individual layups can later be laminated together to form the complete device, and functional components can be released with additional laser micromachining (Figure 2).

Figure 2. Monolithic Bee material layers stacked in a layup for press curing

After removal of the fully machined and laminated layup, the “Monolithic Bee” device is removed in its superplanar form shown in Figure 3. At this point, the 2D planar device is assembled by “pop-up” using a few assembly degrees of freedom built into the device’s structure. The final 3D “pop-up” form of the Monolithic Bee" device, shown in Figure 4, then has its assembly degrees of freedom frozen in place using dip or wave soldering, completing the fabrication process.

Figure 3. Monolithic Bee robot after release from scrap materials

Figure 4. Completed Monolithic Bee robot after “pop-up” assembly

The “Monolithic Bee” is an only illustrative example of precision, process versatility (materials and geometric patterns, and high degree of device complexity and articulation that the invented process affords to the manufacture of millimeter-scale mechanisms. This technology is currently being expanded to (1) include additional material types and greater numbers of layers, (2) incorporate passive energy storage elements (e.g. springs or chemical process) to enable self-assembling devices that fold themselves into place upon energy release, and (3) exploit selective adhesion techniques that allow the fabrication of more complex and highly-articulated mechanical devices (Figures 5 and 6).

Figure 5. A Wright flyer model designed to assemble with a single assembly degree of freedom.

Figure 6. A monolithic chain made using a 3-layer lamination and singulation process.