Mems device having a layer movable at asymmetric rates

Abstract

A microelectromechanical (MEMS) device includes a substrate and a movable layer mechanically coupled to the substrate. The movable layer moves from a first position to a second position at a first rate and from the second position to the first position at a second rate faster than the first rate. The MEMS device further includes an adjustable cavity defined between the substrate and the movable layer and containing a fluid. The MEMS device further includes a fluid conductive element through which the fluid flows at a first flowrate from inside the cavity to outside the cavity upon movement of the movable layer from the second position to the first position and through which the fluid flows at a second flowrate slower than the first flowrate from outside the cavity to inside the cavity upon movement of the movable layer from the first position to the second position.

1 . An electromechanical device comprising:
 a substrate comprising an insulating layer;   a movable layer mechanically coupled to the substrate, the insulating layer on a portion of the substrate facing the movable layer, the movable layer movable between a first position and a second position with respect to the substrate, wherein the movable layer is configured to move from the first position to the second position at a first rate and wherein the movable layer is configured to move from the second position to the first position at a second rate that is faster than the first rate; and   an adhesive layer comprising a different material than the insulating layer, the adhesive layer on at least a portion of the substrate or the movable layer, the adhesive layer configured to increase adhesion between the movable layer and the substrate when the movable layer is in the position of the first position and the second position that is closer to the substrate.   
   
   
       2 . The device of  claim 1 , wherein the second rate is about 100 times faster than the first rate. 
   
   
       3 . The device of  claim 1 , wherein the second position is further from the substrate than is the first position. 
   
   
       4 . The device of  claim 1 , wherein the device is substantially reflective to incident light when the movable layer is in the first position and wherein the device is substantially non-reflective to incident light when the movable layer is in the second position. 
   
   
       5 . The device of  claim 1 , wherein the adhesive layer is on a portion of the substrate. 
   
   
       6 . The device of  claim 1 , wherein the adhesive layer is on a portion of the movable layer facing away from the substrate. 
   
   
       7 . The device of  claim 1 , wherein the adhesive layer is on a portion of the movable layer facing towards the substrate. 
   
   
       8 . The device of  claim 1 , wherein the adhesive layer comprises a material selected from the group consisting of water, organic material, inorganic material, and a self-assembled monolayer. 
   
   
       9 . The device of  claim 1 , further comprising:
 a display;   a processor in electrical communication with the display, the processor configured to process image data; and   a memory device in electrical communication with the processor.   
   
   
       10 . The device of  claim 9 , further comprising a driver circuit configured to send at least one signal to the display. 
   
   
       11 . The device of  claim 10 , wherein the driver circuit is compatible with a super twisted nematic (STN) display. 
   
   
       12 . The device of  claim 10 , wherein the driver circuit is configured to refresh the display at a frequency greater than about once per 30 milliseconds. 
   
   
       13 . An electromechanical device comprising:
 means for supporting a MEMS device, the supporting means comprising means for insulating;   means for reflecting light, the light reflecting means mechanically coupled to the supporting means, the insulating means on a portion of the supporting means facing the reflecting means, the reflecting means movable between a first position and a second position with respect to the supporting means, wherein the reflecting means is configured to move from the first position to the second position at a first rate and wherein the reflecting means is configured to move from the second position to the first position at a second rate faster than the first rate; and   means for increasing adhesion between the reflecting means and the supporting means when the reflecting means is in the position closer of the first position and the second position that is closer to the supporting means, the adhesion increasing means comprising a different material from the insulating means, the adhesion increasing means on at least a portion of the supporting means or the reflecting means.   
   
   
       14 . The device of  claim 13 , wherein the adhesion increasing means comprises at least one of water, an organic material, an inorganic material, and a self-assembled monolayer. 
   
   
       15 . A method of manufacturing an electromechanical device comprising:
 providing a substrate including an insulating layer;   forming a sacrificial layer on the substrate;   forming a movable layer on the sacrificial layer, the insulating layer on a portion of the substrate facing the movable layer;   forming an adhesive layer on at least a portion of the substrate or the movable layer, the adhesive layer different from the insulating layer; and   removing the sacrificial layer, wherein the movable layer is movable between a first position and a second position, wherein the movable layer is configured to move from the first position to the second position at a first rate and wherein the movable layer is configured to move from the second position to the first position at a second rate that is faster than the first rate, the adhesive layer increasing adhesion between the movable layer and the substrate when the movable layer is in the position closer to the substrate.   
   
   
       16 . The method of  claim 15 , wherein forming the adhesive layer is performed after forming the sacrificial layer. 
   
   
       17 . The method of  claim 16 , wherein forming the adhesive layer comprises producing a substantially smooth surface of the sacrificial layer facing the movable layer. 
   
   
       18 . The method of  claim 17 , wherein producing the substantially smooth surface comprises chemical mechanical polishing the sacrificial layer. 
   
   
       19 . The method of  claim 17 , wherein producing the substantially smooth surface comprises electro-chemical etching the sacrificial layer. 
   
   
       20 . The method of  claim 17 , wherein producing the substantially smooth surface comprises dry etching the sacrificial layer. 
   
   
       21 . The method of  claim 17 , wherein producing the substantially smooth surface comprises atomic layer dry etching the sacrificial layer. 
   
   
       22 . The method of  claim 15 , wherein the adhesive layer comprises a layer of water, a layer of organic material, a layer of inorganic material, or a self-assembled monolayer.