Direct acting vertical thermal actuator

Abstract

A micrometer sized, single-stage, vertical thermal actuator capable of repeatable and rapid movement of a micrometer-sized optical device off the surface of a substrate. The vertical thermal actuator is constructed on a surface of a substrate. At least one hot arm has a first end anchored to the surface and a free end located above the surface. A cold arm has a first end anchored to the surface and a free end. The cold arm is located above the hot arm relative to the surface. A member mechanically and electrically couples the free ends of the hot and cold arms such that the member moves away from the substrate when current is applied to at least the hot arm. The hot arm can optionally include a grounding tab to minimize thermal expansion of the cold arm.

What is claimed is:  
     
         1 . A microelectrical mechanical actuator, comprising: 
 (a) a planar substrate;    (b) a first member having first and second ends and wherein the first end of the first member is coupled to the substrate and the first member has a first electrical conductivity;    (c) a second member having first and second ends and wherein the first end of the second member is coupled to the substrate and the second ends of the first and second member are coupled together and the second member has a second electrical conductivity; and    (d) wherein electrical current is conducted along the first member and the second member causing thermal expansion of the first and second members and the first and second members expand at different rates thereby causing the second ends of the members to move away from the substrate.    
     
     
         2 . The microelectrical mechanical actuator of  claim 1  wherein the first member includes a conductor material and a semiconductor material.  
     
     
         3 . The microelectrical mechanical actuator of  claim 1  wherein the first member includes a low resistivity layer coupled thereto along a length thereof.  
     
     
         4 . A microelectrical mechanical actuator comprising: 
 (a) a planar substrate;    (b) a first member having first and second ends and a first elongate portion located there between, wherein the first end is fixedly coupled to the substrate and the first elongate portion is arranged to extend over the substrate such that the longitudinal axis of the first elongate portion is substantially parallel to the plane of the substrate and is located a first distance above the substrate; and    (c) a second member having first and second ends and a second elongate portion located there between, wherein the first end is fixedly coupled to the substrate and the second elongate portion is arranged to extend over the substrate such that the longitudinal axis of the second elongate portion is substantially parallel to the plane of the substrate and is located a second distance above the substrate, and the second ends of the first and second members are coupled so that electrical current can flow through the first member to and through the second member;    (d) wherein the first distance of the first elongate portion is not equal to the second distance of the second elongate portion; and    (e) wherein Joule heating occurs when electrical current flows through the first and second members and the first member undergoes a first amount of thermal expansion, and the second member undergoes a second amount of thermal expansion that is not equal to the first amount of thermal expansion of the first member, so that the coupled second ends of the first and second members move relative to the substrate.    
     
     
         5 . The microelectrical mechanical actuator of  claim 4  wherein the second elongate portion comprises a first and second leg and the first leg is located proximate a first side of the first member and the second leg is located proximate a second side of the first member.  
     
     
         6 . The microelectrical mechanical actuator of  claim 4  wherein the second elongate portion comprises a first and second leg and the first leg is located proximate and outboard a first side of the first member and the second leg is located proximate and outboard a second side of the first member.  
     
     
         7 . The microelectrical mechanical actuator of  claim 4  wherein the first member includes a low electrical resistance layer so that an electrical resistance of the first member is less than an electrical resistance of the second member whereby less Joule heating occurs in the first member than in the second member when current is conducted along the first and second members.  
     
     
         8 . The microelectrical mechanical actuator of  claim 4  wherein the first member comprises conductor material and semiconductor material.