Electrothermal Microactuator Vertical Displacement Lateral Shift
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Solution Overview
Problem
Existing microactuators for large vertical displacement in biomedical imaging applications, such as OCT and confocal microscopy, suffer from significant lateral shift and tilting issues, which distort images and reduce the effective optical aperture size.
Innovation Solution
A microactuator design utilizing a pair of bimorph beams with a rotating rigid frame and additional mechanical support to achieve large vertical displacement with negligible lateral shift, incorporating a symmetric structure of four identical actuators to compensate for angular motion and maintain a flat platform, allowing for controlled tilting and 1D/2D scanning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If conventional electrothermal actuation with two sets of complementarily-oriented thermal bimorph beams is used, then large vertical displacement (hundreds of microns) is achieved, but significant lateral shift occurs (e.g., 0.42 mm lateral shift for 0.71 mm vertical displacement)
Solution Approach 1:
The patent uses asymmetric beam length design where the first bimorph beam has a different length than the second bimorph beam. This asymmetry allows the beams to generate different thermal expansion forces that compensate for each other's lateral shift, enabling large vertical displacement while minimizing lateral shift. The longer beam compensates for the lateral shift of the shorter beam through differential thermal actuation.
Solution Approach 2:
The patent employs counterbalancing thermal beams where the first and second bimorph beams are oriented to generate opposing lateral forces. When both beams are actuated simultaneously, their lateral shifts counterbalance each other, resulting in net vertical displacement with minimal lateral shift. This is achieved by positioning the beams on opposite sides of the platform and actuating them with complementary thermal signals.
2Length of moving object
If conventional electrothermal actuation is used, then large vertical displacement is achieved, but the platform experiences tilting and rotation
Solution Approach 1:
The patent uses asymmetric beam length design where the first bimorph beam has a different length than the second bimorph beam. This asymmetry allows the beams to generate different thermal expansion forces that compensate for each other's lateral shift, enabling large vertical displacement while minimizing lateral shift. The longer beam compensates for the lateral shift of the shorter beam through differential thermal actuation.
Solution Approach 2:
The patent employs counterbalancing thermal beams where the first and second bimorph beams are oriented to generate opposing lateral forces. When both beams are actuated simultaneously, their lateral shifts counterbalance each other, resulting in net vertical displacement with minimal lateral shift. This is achieved by positioning the beams on opposite sides of the platform and actuating them with complementary thermal signals.
3Length of moving object
If two sets of complementarily-oriented thermal bimorph beams are used, then vertical displacement is achieved, but a certain ratio of driving voltages must be maintained to obtain purely vertical motion
Solution Approach 1:
The patent uses asymmetric beam length design where the first bimorph beam has a different length than the second bimorph beam. This asymmetry allows the beams to generate different thermal expansion forces that compensate for each other's lateral shift, enabling large vertical displacement while minimizing lateral shift. The longer beam compensates for the lateral shift of the shorter beam through differential thermal actuation.
Solution Approach 2:
The patent employs counterbalancing thermal beams where the first and second bimorph beams are oriented to generate opposing lateral forces. When both beams are actuated simultaneously, their lateral shifts counterbalance each other, resulting in net vertical displacement with minimal lateral shift. This is achieved by positioning the beams on opposite sides of the platform and actuating them with complementary thermal signals.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design achieves vertical displacement of up to 1 mm with minimal lateral shift and tilting, enabling precise axial scanning and 3D imaging in biomedical applications like endoscopic OCT and confocal microscopy, improving image quality and optical aperture size.
Implementation Method 1
The temperature-induced motion is caused by the thermal expansion coefficient difference of the two materials forming the bimorphs
Implementation Method 2
The second is electrothermal actuation, which is capable of hundreds of microns vertical scanning at low driving voltages
Data Source
AI summary
A microactuator for displacing a platform vertically with respect to a substrate includes a first rigid frame, a first flexible bimorph beam connecting the first frame to the substrate, a second rigid frame, a second flexible bimorph beam connecting the second frame to the first frame, and a third flexible bimorph beam connecting a platform to the second frame. Activation of the first, second, and third flexible bimorph beams allows vertical displacement of the platform with respect to the substrate, with negligible lateral shift. A microactuator assembly includes a substrate, a plurality of first rigid frames, a plurality of first flexible bimorph beams, a plurality of second rigid frames, a plurality of second flexible bimorph beams, a platform, and a plurality of third flexible bimorph beams. Activation of the first, second, and third bimorph beams allows vertical displacement of the platform with respect to the substrate, with negligible lateral shift. A further embodiment with four identical such microactuators oriented at four sides of the platform, can achieve 1D or 2D angular scanning of the mirror plate by the activation of 1 or 2 adjacent microactuators.