Abstract
Large-displacement microelectromechanical system (MEMS) scanners are in high demand for a wide variety of optical applications. Kirigami, a traditional Japanese art of paper cutting and folding, is a promising engineering method for creating out-of-plane structures. This paper explores the feasibility and potential of a kirigami-inspired electrothermal MEMS scanner, which achieves large vertical displacement by out-of-plane film actuation. The proposed scanner is composed of film materials suitable for electrothermal self-reconfigurable folding and unfolding, and microscale film cuttings are strategically placed to generate large displacement. The freestanding electrothermal kirigami film with a 2 mm diameter and high fill factor is completely fabricated by careful stress control in the MEMS process. A 200 μm vertical displacement with 131 mW and a 20 Hz responsive frequency is experimentally demonstrated as a unique function of electrothermal kirigami film. The proposed design, fabrication process, and experimental test validate the proposed scanner’s feasibility and potential for large-displacement scanning with a high fill factor.
Highlights
Microelectromechanical system (MEMS) scanners with large vertical actuation of both the micromirror and microlens have a wide range of applications, including optical pickup [1], multiphoton microscopy [2], Fourier transform spectrometry [3,4], confocal microscopy [5], optical coherence tomography [6], and micro optical diffusion sensing [7,8,9]
Zhang et al [14] presented a lateral shift-free actuator design using three bimorph hinges and two multimorph segments to compensate for the lateral shift. Their actuator achieved a vertical displacement of 320 μm
We explore the feasibility and potential of a kirigami-inspired electrothermal MEMS scanner that enables large vertical actuation with a high fill factor
Summary
Microelectromechanical system (MEMS) scanners with large vertical actuation of both the micromirror and microlens have a wide range of applications, including optical pickup [1], multiphoton microscopy [2], Fourier transform spectrometry [3,4], confocal microscopy [5], optical coherence tomography [6], and micro optical diffusion sensing [7,8,9]. Jamal et al [37] reported that a differential photo-crosslinked epoxy polymer, SU-8, was reversibly folded and unfolded by de-solvation and re-solvation to develop microfluidic devices that flatten out and curl up These folding and unfolding mechanisms are not applicable to the fast-scanning MEMS actuator that is necessary for electrical control on a microscale. Based on the concept of a thermal bimorph being folded and unfolded by the thermal expansion difference induced by Joule heating and natural cooling, the freestanding kirigami film on which bimorphs are placed is electrothermally folded into an out-of-plane structure In this design, the film material combinations suitable for electrothermal self-reconfigurable folding and unfolding are determined, and the kirigami cuttings and thermal bimorphs are aligned to generate vertical displacement with a high area efficiency. The potential of fast, large-displacement scanning with a high fill factor is experimentally examined
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