Characterizations and Micro-assembly of Electrostatic Actuators for 3-DOF Micromanipulators in Laser Phonomicrosurgery.

International audienceThis paper presents a design of electrostatic actuators for 3-DOF micromanipulators in robot-assisted laser phonomicrosurgery. By integrating three sets of electrostatic actuators in a vertical configuration, scanning micro-mirror canbe used as a manipulator for laser source. Key enable technology for these miniaturized actuators is microfabrication processes for microelectromechanical systems (MEMS) because the processes can create submicron features with high precision, mass productive, and low cost. Based on precise micromachined electrostatic actuators, the platform is assembled using micro assembly approach. With sizes less than 5 mm x 5 mm x 5 mm, the proposed design has three degree-of-freedom: two rotational motions around the in-plane axis and one out-of-plane translational motion. Static and dynamic analysis of the device is simulated by Finite Element Analysis (FEA) and compared to theoretical calculations. This system preserves outstanding characteristics of electrostatic actuators for fast response and low power consumption. By micro-assembly of the scanning micromirror, the endoscopic systems can be created with a high range of motion and high scanning speed. The target applications of this system include laryngeal microsurgery, optical coherence tomography (OCT), and minimally invasive surgeries (MIS)

Resonant Adaptive Mirrors

Deformable mirrors (DMs) are integrated into adaptive optical (AO) systems to compensate for wavefront aberrations. These aberrations degrade the image resolution of telescopes, microscopes, ophthalmoscopes, and optical coherent tomographs. The objective of the DM in these applications is to compensate for wavefront aberrations. Continuous and segmented DMs utilize a variety of mechanisms such as electrostatic, piezoelectric, and electromagnetic actuation. Micro-electromechanical systems (MEMS) DMs have the advantages of low cost, low power consumption, and high electrode density. As the electrode count increases, the possibility of the desired modes corresponding to the Zernike modes appearing increases. However, the complexity of the static actuation also increases. In ophthalmology, fth order Zernike modes are used to categorize the aberrations induced by the human eye. These aberrations would degrade the image resolution of the retina during laser scanning. Therefore, a dynamically continuous DMs were developed and actuated at a natural frequency corresponding to the desired Zernike mode. The actuations would drive the mirror plate to deform into the shape of the desired mode. Multiple modes corresponding to low- and high-order Zernike modes were obtained. Resonant DMs exploit the dynamic ampli cation available at natural frequency's in order to reduce voltage and power requirements. This will also reduce the requirements for spatial control of individual electrodes' voltage. However, the use of circular mirror plates to create the electromechanical modes has led to the appearance of degenerate modes (pairs of almost identical modes with closely spaced frequencies). Electrostatic elds were designed to separate those modes and help break coupling between them. The elds employ selectively, actuating some of the electrodes under the DM while grounding the rest. An AC voltage was applied to selective scheme of electrodes in order to induced mode shapes that are corresponding to the Zernike modes. This design relies on a new technique which uses pulsed laser scanning instead of continuous laser scanning. The proposed DM was designed and fabricated using a Micra-GEM fabrication process. Simulations using the nite element method (FEM) software COMSOL were used in order to determine the natural frequencies and mode shapes, and to separate degenerate modes natural frequencies by applying electrostatic elds that increase the di erence between them. Characterization of the DM was conducted using laser Doppler vibrometer to identify the mode shapes and its natural frequencies experimentally. The stroke measurements of the target DM were shown as a function of frequency and amplitude. In addition, RMS error measurements were used as a comparison between DM modes and there corresponding Zernike mode. The aim of this research was to over come the in uence function due to mechanical coupling in the continuous DMs. In uence function requires di erent voltages that apply to electrode scheme. Therefore, static actuation of the DMs rely on a complex driving circuits. Resonant DMs eliminate the e ect of the in uence function by triggering the mirror via its natural frequencies. They reduce the number of red electrode scheme by applying single voltage to the electrodes. As a result, they reduce the complexity of the driving circuits that require to control its shape. This research requires a new technique of using a pulsed laser instead of a continuous laser for the proposed DM. This may lead to manipulation of the optical laser signal using the mirror as a part of the signaling process. This should be completed by synchronizing the frequencies of both the DM and the laser to produce a high resolution image of the retina

MEMS Technology for Biomedical Imaging Applications

Biomedical imaging is the key technique and process to create informative images of the human body or other organic structures for clinical purposes or medical science. Micro-electro-mechanical systems (MEMS) technology has demonstrated enormous potential in biomedical imaging applications due to its outstanding advantages of, for instance, miniaturization, high speed, higher resolution, and convenience of batch fabrication. There are many advancements and breakthroughs developing in the academic community, and there are a few challenges raised accordingly upon the designs, structures, fabrication, integration, and applications of MEMS for all kinds of biomedical imaging. This Special Issue aims to collate and showcase research papers, short commutations, perspectives, and insightful review articles from esteemed colleagues that demonstrate: (1) original works on the topic of MEMS components or devices based on various kinds of mechanisms for biomedical imaging; and (2) new developments and potentials of applying MEMS technology of any kind in biomedical imaging. The objective of this special session is to provide insightful information regarding the technological advancements for the researchers in the community

MEMS Devices for Circumferential-scanned Optical Coherence Tomography Bio-imaging

Ph.DDOCTOR OF PHILOSOPH

Recent advances in MEMS-VCSELs for high performance structural and functional SS-OCT imaging

Since the first demonstration of swept source optical coherence tomography (SS-OCT) imaging using widely tunable micro-electromechanical systems vertical cavity surface-emitting lasers (MEMS-VCSELs) in 2011, VCSEL-based SSOCT has advanced in both device and system performance. These advances include extension of MEMS-VCSEL center wavelength to both 1060nm and 1300nm, improved tuning range and tuning speed, new SS-OCT imaging modes, and demonstration of the first electrically pumped devices. Optically pumped devices have demonstrated continuous singlemode tuning range of 150nm at 1300nm and 122nm at 1060nm, representing a fractional tuning range of 11.5%, which is nearly a factor of 3 greater than the best reported MEMS-VCSEL tuning ranges prior to 2011. These tuning ranges have also been achieved with wavelength modulation rates of >500kHz, enabling >1 MHz axial scan rates. In addition, recent electrically pumped devices have exhibited 48.5nm continuous tuning range around 1060nm with 890kHz axial scan rate, representing a factor of two increase in tuning over previously reported electrically pumped MEMS-VCSELs in this wavelength range. New imaging modes enabled by optically pumped devices at 1060nm and 1300nm include full eye length imaging, pulsatile Doppler blood flow imaging, high-speed endoscopic imaging, and hand-held wide-field retinal imaging.National Institutes of Health (U.S.) (Grant R44EY022864-01)National Institutes of Health (U.S.) (Grant R44EY022864-02)National Institutes of Health (U.S.) (Grant R44CA101067-05)National Institutes of Health (U.S.) (Grant R44CA101067-06)National Institutes of Health (U.S.) (Grant R44CA101067-07)National Institutes of Health (U.S.) (Grant R01-EY011289-26)National Institutes of Health (U.S.) (Grant R01-CA075289-15)National Institutes of Health (U.S.) (Grant R01-EY013178-12)National Institutes of Health (U.S.) (Grant R01-EY013516-09)National Institutes of Health (U.S.) (Grant R01-EY018184-05)National Institutes of Health (U.S.) (Grant R01-NS057476-05)United States. Air Force Office of Scientific Research (Grant FA9550-10-1-0551)United States. Air Force Office of Scientific Research (Grant FA9550-12-1-0499)Thorlabs, Inc

MEMS-Based Endoscopic Optical Coherence Tomography

Early cancer detection has been playing an important role in reducing cancer mortality. Optical coherence tomography (OCT), due to its micron-scale resolution, has the ability to detect cancerous tissues at their early stages. For internal organs, endoscopic probes are needed as the penetration depth of OCT is about 1–3 mm. MEMS technology has the advantages of fast speed, small size, and low cost, and it has been widely used as the scanning engine in endoscopic OCT probes. Research results have shown great potential for OCT in endoscopic imaging by incorporating MEMS scanning mirrors. Various MEMS-OCT designs are introduced, and their imaging results are reviewed in the paper

Optical MEMS

Optical microelectromechanical systems (MEMS), microoptoelectromechanical systems (MOEMS), or optical microsystems are devices or systems that interact with light through actuation or sensing at a micro- or millimeter scale. Optical MEMS have had enormous commercial success in projectors, displays, and fiberoptic communications. The best-known example is Texas Instruments’ digital micromirror devices (DMDs). The development of optical MEMS was impeded seriously by the Telecom Bubble in 2000. Fortunately, DMDs grew their market size even in that economy downturn. Meanwhile, in the last one and half decade, the optical MEMS market has been slowly but steadily recovering. During this time, the major technological change was the shift of thin-film polysilicon microstructures to single-crystal–silicon microsructures. Especially in the last few years, cloud data centers are demanding large-port optical cross connects (OXCs) and autonomous driving looks for miniature LiDAR, and virtual reality/augmented reality (VR/AR) demands tiny optical scanners. This is a new wave of opportunities for optical MEMS. Furthermore, several research institutes around the world have been developing MOEMS devices for extreme applications (very fine tailoring of light beam in terms of phase, intensity, or wavelength) and/or extreme environments (vacuum, cryogenic temperatures) for many years. Accordingly, this Special Issue seeks to showcase research papers, short communications, and review articles that focus on (1) novel design, fabrication, control, and modeling of optical MEMS devices based on all kinds of actuation/sensing mechanisms; and (2) new developments of applying optical MEMS devices of any kind in consumer electronics, optical communications, industry, biology, medicine, agriculture, physics, astronomy, space, or defense

MEMS based catheter for endoscopic optical coherence tomography

Ph.DDOCTOR OF PHILOSOPH

Zernike generation with MEMS deformadle mirror actuated by electrostatic piston array

2018 IEEE Micro Electro Mechanical Systems (MEMS), 21-25 Jan. 2018.We report a low-voltage and large-displacement electrostatic deformable mirror for in vivo retinal imaging by adaptive-optics optical coherence tomography. The mirror utilizes an electrostatic piston actuator which allows bottom electrodes to move vertically to keep the gap small to maintain large actuation force at low actuation voltage. An 8-mm-diameter mirror device was fabricated from two components; the mirror part and the actuator part. The parts were assembled with 7-μm-gap defined by an SU-8 layer. We successfully demonstrated operation of the mirror in various Zernike modes