Method for forming an actuator array device

#The present invention relates to microactuators having macroscopic force and displacement. More particularly, the invention relates to microactuators comprising a 3-D array of small actuator cells, which are formed from stacked substrate sheets having an electrode layer on only one side of the substrate sheet.

#Most microactuator arrays, used as MEMS (Micro-Electro-Mechanical-Systems) devices, are fabricated in silicon. Despite the many favorable attributes of silicon, it is not always a suitable or ideal material for every application of MEMS. Silicon is brittle and subject to breaking, particularly as the total device size increases. This brittleness limits devices, especially actuators, to relatively small sizes capable of only small displacements and forces. The shapes that can be realized in silicon are typically restricted by crystalline planes or 2-D fabrication processes, and more complicated structures often result in prohibitively high cost and low yield. It would be of great advantage to the art if another material, other than silicon, could be used for MEMS and actuators. In particular, it would be advantageous if the structure used to fabricate the actuator required significantly fewer electrode layers with no substantial loss in force, while requiring less power to operate.

#The present invention provides an electrostatic microactuator array device including a plurality of sheet pairs secured together over the sheet pair lengths and widths. The sheet pairs can be formed of a first sheet and a second sheet, wherein the first and second sheets have a front and back surface. The first and second sheets preferably have a substrate layer disposed toward the sheet back surface, a dielectric layer disposed toward the sheet front surface, and a conductive layer disposed between the substrate layer and the dielectric layer. Voltage applied to the conductive layers causes an attractive electrostatic force between the first and second sheets. The first and second sheet front surfaces are secured together at a number of spaced bonding locations along the sheet lengths and widths, such that the first and second sheets have a plurality of non-bonded regions between the bonding locations. In this configuration, the sheet pairs have outer surfaces formed of the back surfaces of the first and second sheets. The outer surfaces of the adjacent sheet pairs are secured together over the sheet pair lengths and widths to form an array of sheet pairs.

#FIG. 1 is a partial cut-away perspective view of a microactuator using polymer sheets;

#FIG. 2 is a schematic, partially cut-away and in section view of a microactuator formed of a plurality of unit cells with a center polymer sheet;

#FIG. 3 is a schematic, partially cut-away and in section view of a microactuator formed of a plurality of unit cells with no center polymer sheet;

#FIG. 1 is a partial cut-away perspective view of a microactuator using polymer sheets. The illustrative microactuator is formed by stacking and bonding together multiple polymer sheets, as described in for example, U.S. patent application Ser. No. 09/233,368 to Cabuz et al., filed Dec. 29, 1998, entitled “POLYMER MICROACTUATOR ARRAY WITH MACROSCOPIC FORCE AND DISPLACEMENT”, now U.S. Pat. No. 6,184,608; and to U.S. patent application Ser. No. 09/476,667 to Horning, filed Dec. 30, 1999, entitled “MICROACTUATOR ARRAY WITH INTEGRALLY FORMED PACKAGE”, now U.S. Pat. No. 6,411,013, both of which are incorporated herein by reference.

#As described in the above references, electrodes from selected sheets can be electrically tied together or can be individually addressed, depending on the degree of control and sophistication of the end use, noting that individual addressing requires more connections, so it would involve higher cost but finer control when needed. Electrical contact between layers and sheets can be made through flexible plastic interconnect straps, as described in U.S. patent application Ser. No. 09/233,368 to Cabuz et al., now U.S. Pat. No. 6,184,608, or through an integrally formed package, as described in U.S. patent application Ser. No. 09/476,667 to Horning, now U.S. Pat. No. 6,411,013.

#In either case, the top of the microactuator stack may be secured to an upper housing 42, and the bottom of the microactuator stack is secured to a lower housing 48. The upper and/or lower housings 42 and 48 may include an external connector 50 and control circuitry 52 for controlling the microactuator. The upper and/or lower housing 42 and 48 may further include one or more levels of metal interconnects, as in a printed circuit board, to route the inputs of the external connector 50 through the control circuitry 52 and to the sheets of the actuator using one or more of the flexible interconnect straps.