Understanding Smart Sensors - Nomads.usp

MEMS Beyond Sensors 221Methods for actuating the artificial arms on robotic devices have beenstudied and compared to properties of nature’s actuators: muscles [29]. One ofthe more interesting developments is an electrostatic muscle that uses the combinationof a number of small force displacements to produce significant displacement[30]. Integrated force arrays produce a flexible membrane thatcontracts with an applied electric field. Surface micromachining is used to createmetal-clad polyimide rectangles that are only a few millimeters on a side. Anarray of 1.5 million cells forms a 1-cm-long fiber that contracts 0.3 cm withonly a few volts applied. The force-array technology is being developed forcoordinated movement of interlocking flexible elements. Besides robotics, selfalignedhigh-density multicontact electrical connectors can be designed usingthis technology.9.3.10 MicronozzlesMicrominiature apertures and nozzles are required for optical instruments anda variety of mechanical devices, including high-resolution ink jet printers, flowcontrol, and atomizers [31]. The micronozzle used for ink jet printers is thehighest volume production microactuator. Sacrificial etching is used to producea highly cusped nozzle-shaped structure using silicon nitride. A mold is createdfor the nitride by steps (a) through (d) in Figure 9.17. The nitride structure is(a)(d)Silicon(b)NitrideOxidePolymer(f)(c)(e)Figure 9.17 Micronozzle fabrication process.