A 2 degree-of-freedom SOI-MEMS translation stage with closed loop positioning

This research contains the design, analysis, fabrication, and characterization of a closed loop XY micro positioning stage. The XY micro positioning stage is developed by adapting parallel-kinematic mechanisms, which have been widely used for macro and meso scale positioning systems, to silicon-based micropositioner. Two orthogonal electrostatic comb drives are connected to moving table through 4-bar mechanism and independent hinges which restrict unwanted rotation in 2-degree-of-freedom translational stage. The XY micro positioning stage is fabricated on SOI wafer with three photolithography patterning processes followed by series of DRIE etching and HF etching to remove buried oxide layer to release the end-effector of the device. The fabricated XY micro positioning stage is shown in Fig1 with SEM images. The device provides a motion range of 20 microns in each direction at the driving voltage of 100V. The resonant frequency of the XY stage under ambient conditions is 811 Hz with a high quality factor of 40 achieved from parallel kinematics. The positioning loop is closed using a COTS capacitance-to-voltage conversion IC and a PID controller built in D-space is used to control position with an uncertainty characterized by a standard distribution of 5.24nm and a approximate closed-loop bandwidth of 27Hz. With the positioning loop, the rise time and settling time for closed-loop system are 50ms and 100ms. With sinusoidal input of ω=1Hz, the maximum phase difference of 108nm from reference input is obtained with total motion range of 8μm

Multi-spectral Dual Axes Confocal Endomicroscope with Vertical Cross-sectional Scanning for In-vivo Targeted Imaging of Colorectal Cancer

Pathologists review histology cut perpendicular to the tissue surface or in the vertical cross-section (XZ-plane) in order to visualize the normal or abnormal differentiation patterns. The epithelium of hollow organs, such as the colon, is the origin of many important forms of cancer. The vertical cross-section provides a comprehensive view of the epithelium which normally differentiates in the basilar to luminal direction. Real-time imaging in this orientation has not been fully explored in endomicroscopy because most instruments collect images in the horizontal cross-section (XY-plane). Imaging microstructures from the tissue surface to about half a millimeter deep can reveal early signs of disease. Furthermore, the use of molecular probes is an important, emerging direction in diagnostic imaging that improves specificity for disease detection and reveals biological function. Dysplasia is a pre-malignant condition in the colon that can progress into colorectal cancer. Peptides have demonstrated tremendous potential for in-vivo use to detect colonic dysplasia. Moreover, peptides can be labeled with NIR dyes for visualizing the full depth of the epithelium in small animals. This study aims to demonstrate large FOV multi-spectral targeted in-vivo vertical optical section with a dual axes confocal endomicroscope enabled by MEMS technology. The NIR multi-spectral fluorescence images demonstrate both histology-like morphology imaging and molecular imaging of specific peptide binding to dysplasia in the mouse colon. The specific aims of this study are: (1) to develop miniature vertical cross-sectional scan engine based on MEMS technology for imaging on XZ-plane; (2) to integrate micro-optics and develop multi-spectral dual axes confocal endomicroscope imaging system; (3) to perform in-vivo targeted vertical cross-sectional imaging with large FOV on colorectal cancer mouse model.PhDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/107154/1/zqiu_1.pd

MEMS-Based Endomicroscopes for High Resolution in vivo Imaging

Intravital microscopy is an emerging methodology for performing real time imaging in live animals. This technology is playing a greater role in the study of cellular and molecular biology because in vitro systems cannot adequately recapitulate the microenvironment of living tissues and systems. Conventional intravital microscopes use large, bulky objectives that require wide surgical exposure to image internal organs and result in terminal experiments. If these instruments can be reduced sufficiently in size, biological phenomena can be observed in a longitudinal fashion without animal sacrifice. The epithelium is a thin layer of tissue in hollow organs, and is the origin of many types of human diseases. In vivo assessment of biomarkers expressed in the epithelium in animal models can provide valuable information of disease development and drug efficacy. The overall goal of this work is to develop miniature imaging instruments capable of visualizing the epithelium in live animals with subcellular resolution. The dissertation is divided into four projects, where each contains an imaging system developed for small animal imaging. These systems are all designed using laser beam scanning technology with tiny mirrors developed with microelectromechanical systems (MEMS) technology. By using these miniature scanners, we are able to develop endomicroscopes small enough for hollow organs in small animals. The performance of these systems has been demonstrated by imaging either excised tissue or colon of live mice. The final version of the instrument can collect horizontal/oblique plane images in the mouse colon in real time (>10 frames/sec) with sub-micron resolution (<1 um), deep tissue penetration (~200 um) and large field of view (700 x 500 um). A novel side-viewing architecture with distal MEMS scanning was developed to create clear and stable image in the mouse colon. With the use of the instrument, it is convenient to pinpoint location of interest and create a map of the colon using image mosaicking. Multispectral fluorescence images can by collected at excitation wavelength ranging from 445 nm to 780 nm. The instruments have been used to 1) validate specific binding of a cancer targeting agent in the mouse colon and 2) study the tumor development in a mouse model with endogenous fluorescence protein expression. We use these studies to show that we have developed an enabling technology which will allow biologist to perform longitudinal imaging in animal models with subcellular resolution.PHDBiomedical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/136954/2/dxy_1.pd

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

Fab-on-a-chip: a MEMS approach to nanofabrication

Modern semiconductor fabs are multi-billion dollar systems capable of producing devices with features as small as 7 nm for a cost of nano-dollars each. The nanoscale devices they fabricate have reshaped the world. Whole new fields of nanoscience have opened up encouraged by the success of the semiconductor industry and the promise of nanotechnology. Modern nanoscientists largely use tools pioneered in and for semiconductor fabs. Here, some of the functionality of semiconductor fabs is reproduced on millimeter size silicon chips, creating new tools for researching and manufacturing nanodevices. A system of these silicon chips is a fab-on-a-chip and is built using microelectromechanical systems or MEMS. MEMS devices are inexpensive to fabricate, but can be extremely complex. The first fab-on-a-chip device presented is a micro-scale thermal evaporator. It can deposit 7 Å s^-1 of Pb from ∼1 mm away, can be rapidly reloaded using simple mechanical means, and has a footprint of 0.25 mm^2. The flux rate from this thermal evaporator is monitored using a re-purposed quartz crystal oscillator as a mass sensor. Another fab-on-a-chip device is a writer. A device capable of positioning a silicon plate with <10 nm resolution in two dimensions. It can be used either to position stencils of nanoscale devices or to draw nanoscale devices directly in a process called atomic calligraphy. A micro-evaporator has been connected to a writer to form a device that is capable of producing nanoscale structures while only being a few cubic millimeters large. Additionally, an advanced writer is presented that can move a plate with five degrees of freedom and could be a powerful tool for fabricating and manipulating nanodevices

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

Microfabricated tools for nanoscience

Recent developments and advances in micro-electro-mechanical systems for nanometer-scale applications such as scanning force microscopy are presented. The microfabrication of tools so small that they enable access to the nanoworid, such as tips, flexible cantilevers, integrated deflection sensors and nanoactuators will be described. Bulk and surface micromachining of mono or polycrystalline silicon, extended by aligned-wafer-bonding, etch-back and sacrificial-iayer-etching steps are major fabrication steps used. Experiments on prototypes show that these devices are promising for use as ultra-sensitive stand-alone local probe micro-instruments