Improved design of polymeric composite electrothermal micro-actuator for high track density hard disk drives

Abstract

Improved design of polymeric composite electrothermal micro-actuator for high track density hard disk drives.

An electro-thermally activated rotary micro-positioner for slider-level dual-stage positioning in hard disk drives

“…At this areal density (corresponding to 1 million tracks per inch (TPI)), the data track is as fine as 25 nm wide and the allowable track misregistration is 2.5 nm (3σ value) [1]. Dualstage positioning scheme (see figure 1(a)) can assist the coarse primary driver to achieve finer head-positioning at higher speed [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15]. There are three locations for deploying the dual-stage actuators, namely suspension-level, slider-level, and head-level.…”

“…On the contrary, a better servo bandwidth is possible using the sliderlevel micro-positioner, which is collocated with the read-write head and has a lower inertia. Various micro-actuators have been developed so far for the slider-level micro-positioner: Electrostatic comb drives [4], or electrostatic parallel plates [5,6], piezoelectric unimorphs [7,8], piezoelectric extenders [9][10][11], or electro-thermal micro-actuators [12][13][14][15]. They can move a slider linearly using a translation stage [4,7] or swing the slider using a rotary (angular) stage [5][6][7][8].…”

“…However, most pizoelectrically driven micro-positioners are driven in the push-pull mode by a pair of piezoelectric micro-actuators, either piezoelectric unimorphs [7,8] or extenders [9][10][11]. A thermal micro-actuator, such as a V-shape expansion flexure [12] or a thermal unimorph [13][14][15], produces only a one directional stroke upon heating. A mirrored pair of thermal micro-actuators can produce a bidirectional stroke upon alternate heating, with the active micro-actuator deforming the inactive one [12][13][14][15].…”

“…A thermal micro-actuator, such as a V-shape expansion flexure [12] or a thermal unimorph [13][14][15], produces only a one directional stroke upon heating. A mirrored pair of thermal micro-actuators can produce a bidirectional stroke upon alternate heating, with the active micro-actuator deforming the inactive one [12][13][14][15].…”

“…A new kind of dual-stage micro-positioners has recently been developed based on the thermal expansion of silicon or polymer [12][13][14][15]. The powerful thermal expansion of solids can deform silicon flexure of high rigidity.…”