Mems actuator device with integrated temperature sensors

Abstract

An electro-thermal actuator which includes a unit cell comprising at least one thermal bimorph, the thermal bimorph comprising at least two materials of different thermal expansion coefficient bonded together, the unit cell having a first end and a second end; and at least one temperature sensor located on the at least one thermal bimorph for measuring a temperature of the at least one thermal bimorph and determining a position of the unit cell. The basic structure can be expanded to 1-D, 2-D and 3-D positioners. The bimorphs can also be coupled to an active yoke which is in turn anchored to a plate, in order to reduce the parasitic heat effects on displacement of the tip of the bimorph.

1 - 22 . (canceled) 
     
     
         23 . An electro-thermal actuator for positioning a element relative to a substrate, the electro-thermal actuator including a first actuator having a first end point and a second end point that is movable relative to the first end point, the first actuator comprising:
 a first unit cell having a first end and a second end, the first unit cell comprising a first thermal bimorph;   a first heater that is operative to provide a first heat flow to the first unit cell; and   a first temperature sensor that is operative for measuring a first temperature at a first location, wherein the first temperature is based on a second heat flow between the first unit cell and a second location that is external to the first unit cell;   wherein the position of the second end relative to the first end is based on the first temperature and the first heat flow, and wherein the first actuator is operative for inducing motion of the element along a first direction.   
     
     
         24 . The electro-thermal actuator of  claim 23 , wherein the first unit cell further comprises a second thermal bimorph, the first thermal bimorph and second thermal bimorph being physically coupled in series between the first end and the second end, and the second thermal bimorph being operative for mitigating development of a bending moment at one of the first end and second end, wherein the first thermal bimorph and second thermal bimorph are physically connected such that the first heater is operative to further provide the first heat flow to the second unit cell. 
     
     
         25 . The electro-thermal actuator of  claim 23 , the first actuator further comprising a second temperature sensor that is operative for measuring a second temperature at a third location, wherein the first temperature sensor is located proximate the first end and the second temperature sensor is located proximate the second end;
 wherein the position of the second end relative to the first end is further based on the second temperature.   
     
     
         26 . The electro-thermal actuator of  claim 25 , wherein each of the first location and third location is external to the first unit cell. 
     
     
         27 . The electro-thermal actuator of  claim 23 , wherein the first location is external to the first unit cell. 
     
     
         28 . The electro-thermal actuator of  claim 23 , further comprising a second actuator having a third end point and a fourth end point that is movable relative to the third end point, the second actuator comprising:
 a second unit cell comprising a second thermal bimorph; and   a second heater that is operative to provide a third heat flow to the second unit cell;   wherein the first actuator and second actuator are physically coupled such that the motion of the element is based on the first heat flow, the second heat flow, and the third heat flow, and wherein the second heat flow is based on the third heat flow.   
     
     
         29 . The electro-thermal actuator of  claim 28 , wherein the second actuator is operative for moving the element along a second direction that is orthogonal to the first direction. 
     
     
         30 . The electro-thermal actuator of  claim 23 , wherein the substrate comprises the second location. 
     
     
         31 . The electro-thermal actuator of  claim 23 , the first actuator further comprising a second unit cell having a second thermal bimorph, a third end, and a fourth end, the first unit cell and second unit cell being physically coupled in parallel such that (1) the first end and third end are physically connected at the first end point and collectively define a first plane and (2) the second end and fourth end are physically connected at the second end point. 
     
     
         32 . The electro-thermal actuator of  claim 31 , wherein first actuator is dimensioned and arranged such that the first direction is substantially within the first plane. 
     
     
         33 . The electro-thermal actuator of  claim 31 , wherein first actuator is dimensioned and arranged such that the first direction is substantially orthogonal to the first plane. 
     
     
         34 . The electro-thermal actuator of  claim 31 , further comprising an active yoke for physically coupling the first unit cell and second unit cell at one of the first end point and the second end point, the active yoke comprising a third thermal bimorph that has a length shorter than each of the first thermal bimorph and the second thermal bimorph. 
     
     
         35 . The electro-thermal actuator of  claim 23 , further including a second actuator having a third end point and a fourth end point that is movable with respect to the third end point, the second actuator comprising:
 a second unit cell comprising a second thermal bimorph;   a second heater that is operative to provide a third heat flow to the second unit cell; and   a second temperature sensor that is operative for measuring a second temperature at a third location, wherein the second temperature is based on a fourth heat flow between the second unit cell and a fourth location that is external to the second unit cell;   wherein the position of the fourth end point relative to third end point is based on the second temperature and the fourth heat flow, and wherein the second actuator is operative for moving the element along a second direction that is unaligned with the first direction.   
     
     
         36 . The electro-thermal actuator of  claim 35 , wherein the second direction and the first direction are substantially orthogonal. 
     
     
         37 . The electro-thermal actuator of  claim 35 , further comprising a third actuator having a fifth end point and a sixth end point that is movable along a third direction with respect to the fifth end point, the third actuator comprising:
 a third unit cell comprising a third thermal bimorph;   a third heater that is operative to provide a fifth heat flow to the third unit cell; and   a third temperature sensor that is operative for measuring a third temperature at a fifth location, wherein the third temperature is based on a sixth heat flow between the third unit cell and a sixth location that is external to the third unit cell;   wherein the position of the sixth end relative to third end is based on the third temperature and the fifth heat flow, and wherein the third actuator is operative for moving the element along a third direction, and further wherein the first direction, second direction, and third direction are mutually orthogonal.   
     
     
         38 . The electro-thermal actuator of  claim 23  wherein the substrate defines a first plane, and wherein the element comprises:
 a first piezoresistor; and 
 a second piezoresistor; 
 wherein the first and second piezoresistors are arranged such that they are at substantially the same temperature, and wherein each of the first and second piezoresistor cantilevers from the second end such that the free end of the first piezoresistor projects further away from the first plane than the free end of the second piezoresistor when the first electro-thermal actuator is actuated. 
 
     
     
         39 . An electro-thermal actuator for positioning a element relative to a substrate, the electro-thermal actuator comprising a first actuator operative for translating the element along a first direction, the first actuator comprising:
 a plurality of first unit cells physically coupled in parallel between a first end and a second end, each first unit cell comprising at least one thermal bimorph;   a first heater that is operative to provide a first heat flow to the first actuator; and   a first temperature sensor that is operative for measuring a first temperature at a first location, wherein the first temperature is based on a second heat flow between the plurality of first unit cells and a second location that is external to the plurality of first unit cells;   wherein the position of the element along the first direction is based on the first temperature and the first heat flow.   
     
     
         40 . The electro-thermal actuator of  claim 39 , further comprising an active yoke for coupling at least one first unit cell of the plurality of first unit cells at one of the first end and the second end, the active yoke comprising a thermal bimorph having a shorter length than the thermal bimorph of the at least one first unit cell. 
     
     
         41 . The electro-thermal actuator of  claim 39 , further comprising a second actuator operative for translating the element along a second direction that is substantially orthogonal to the first direction, the second actuator comprising:
 a plurality of second unit cells physically coupled in parallel between a third end and a fourth end, each second unit cell comprising at least one thermal bimorph;   a second heater that is operative to provide a third heat flow to the second actuator; and   a second temperature sensor that is operative for measuring a second temperature at a third location, wherein the second temperature is based on a fourth heat flow between the plurality of second unit cells and a fourth location that is external to the plurality of second unit cells;   wherein the position of the element along the second direction is based on the second temperature and the third heat flow.   
     
     
         42 . The electro-thermal actuator of  claim 41 , further comprising a third actuator operative for translating the element along a third direction, the first direction, second direction, and third direction being substantially mutually orthogonal, and the third actuator comprising:
 a plurality of third unit cells physically coupled in parallel between a fifth end and a sixth end, each third unit cell comprising at least one thermal bimorph;   a third heater that is operative to provide a fifth heat flow to the third actuator; and   a third temperature sensor that is operative for measuring a third temperature at a fifth location, wherein the third temperature is based on a sixth heat flow between the plurality of third unit cells and a sixth location that is external to the plurality of third unit cells;   wherein the position of the element along the third direction is based on the third temperature and the sixth heat flow.   
     
     
         43 . A method for positioning a element relative to a substrate, the method comprising:
 providing a first heat flow to a first actuator that includes a first thermal bimorph, wherein the first actuator is operative for positioning the element along a first direction;   determining a second heat flow between the first actuator and a first location that is external to the first thermal bimorph; and   controlling the first heat flow based on the second heat flow.   
     
     
         44 . The method of  claim 43  wherein the second heat flow is determined by operations comprising:
 measuring a first temperature at a first location that is external to the first actuator; 
 measuring a second temperature at a second location that is external to the first actuator, wherein the first location and second location are separated by a known thermal resistance path; and 
 computing a value for the second heat flow based on the first temperature and the second temperature. 
 
     
     
         45 . The method of  claim 43  further comprising:
 providing a third heat flow to a second actuator that includes a second thermal bimorph, wherein the second actuator is operative for positioning the element along a second direction that is unaligned with the first direction; 
 determining a fourth heat flow between the second actuator and a second location that is external to the second thermal bimorph; and 
 controlling the third heat flow based on the fourth heat flow. 
 
     
     
         46 . The method of  claim 45  further comprising:
 providing a fifth heat flow to a third actuator that includes a third thermal bimorph, wherein the third actuator is operative for positioning the element along a third direction, and wherein the first direction, second direction, and third direction are substantially mutually orthogonal; 
 determining a sixth heat flow between the third actuator and a third location that is external to the third thermal bimorph; and 
 controlling the fifth heat flow based on the sixth heat flow. 
 
     
     
         47 . The method of  claim 43  further comprising:
 providing the first actuator such that it further comprises a second thermal bimorph, wherein the first thermal bimorph and second thermal bimorph are coupled in series between a first end point and a second end point, and wherein the second thermal bimorph is shorter than the first thermal bimorph, and further wherein the second thermal bimorph and first thermal bimorph are arranged such that the development of a bending moment at one of the first end and second end is mitigated.