Research Overview

Rotating Micro-Mirror for OCT Applications
This project aims at developing a micro actuator system for precise transmission and reception of bio-optical signals. The system consists of a first-in-kind polysilicon micro mirror held stationary at a 45° angle on top of a 360°-rotating platform driven by a scratch drive array. The entire system is designed with a 1-mm diameter size constraint. This constraint will allow the device to fit inside the tip of a catheter for use in biomedical endoscopy. We have developed two designs based on a commercial micromachining process to accomplish this. One mirror assembly is pulled into position at 45° while the other mirror assembly flips over itself into place. The benefit of the former mirror is that it can easily be coated with gold to improve reflectivity at the foundry. The benefit of the latter is that the optically-flat bottom surface of the polysilicon layer is used as the reflective surface of the mirror. Photoresist "hinges" are used to allow this system to self-assemble by surface tension induced through heating.
Researchers: TBD
Collaborator: Prof. Zhongping Chen
Publications: C035, C036
Single-Cell Platforms for Microbiomechanics
This project aims at establishing the critical engineering feasibility that will lead to a micro-platform with massive arrays of micro chambers each instrumented with a resonant transducer capable of interrogating the mechanical properties of a cell. In every major cellular events including cell division and cell migration, the cytoskeleton changes dynamically in a highly complex and coordinated manner to help complete the cellular activities. Since many of the mechanical properties of a cell are defined by cytoskeleton morphology, including viscosity and stiffness, it is hypothesized that viscosity and stiffness measurements can be used to infer the different morphological behaviors of cytoskeleton, which in turns are directly driven by cellular activities. Conventional molecular probes will be used to simultaneously visualize cytoskeleton changes while resonance is measured. Such correlation does not yet exist, but holds tremendous promise in enabling massively parallel drug screening, cancerous cells identification and quantification, and other rapid turn-around studies of single-cell physiologies.
Researchers: Yu-Hsiang (Shawn) Hsu, Cathy Lu, Sweta Gupta, Gelareh Eslamian, Derek Tam, Henry Wong
Strain Gauge Arrays for Biological Tissues
This project aims at developing two types of flexible, implantable sensor arrays (1) for measuring surface strain on live bones and (2) for measuring strain distributions on soft biological tissues. Monitoring strain within biological tissues in real time will help better understand biomechanical behaviors of the tissues and facilitate the development of biomechanical prostheses, diagnostic devices and assistive rehabilitation. However, currently available devices for measuring strain are too large (typically 2 ~ 5 mm) to provide measurements with suitable resolution. These gauges are also difficult to mount on hard tissues, such as bone, because of their large size and the bone's irregular surface topology. In addition, they cannot sustain the high strain level (as much as 30%) of those in soft tissues including muscles, ligaments, tendons, and heart valves. In this research, the strain sensitivities obtained from the Parylene-based strain gauge were found to be higher than those of the commercial gauges. The three-point bending on the chicken tibia demonstrated the capability of the strain gauges monitoring the surface strains in real-time, even up to the fracture point of the bone. We have also done feasibility studies of the carbon black filled polydimethylsiloxane (PDMS) as the sensing element for strain measurement of soft tissues. The high sensitive piezoresistive and flexible behavior of the composite device was observed, with on-going activities to further develop it into strain gauges for soft tissues.
Researchers: TBD
Collaborator: Prof. Joyce H. Keyak
Publications: C028, C037, C039
Mechanical Tension on Neurogenesis
This Project aims at developing a platform to elucidate the role of mechanical tension in cerebral cortex development. It is thought that mechanical tension is a major driving force for many aspects of morphogenesis within the central nervous system, but this possibility has been intractable experimentally using traditional approaches. We intend to quantify the relationship between tension and its effect on neurogenesis. In this study, slices of embryonic mouse brain tissue are adhered to flexible poly-dimethyl siloxane (PDMS) membranes using fibrin gel. The PDMS membrane is part of the platform that can be set to extert a quantified amount of strain on the PDMS. Computer simulations are done to understand the actual strain on the tissues as a result of the applied displacement. The final version of the platform will consist of a piezoelectric actuation mechanism to systematically vary and quantify the applied strain.
Researchers: Evan Yu, Ouwen Liang, Jonathan Yu, Jennifer Nguyen, Derek Tam
Collaborator: Prof. Edwin S. Monuki
Publications: C034, C040
Brain Compliance Platform (Completed)
This Project aims at developing a MEMS-based platform to quantify the mechanical compliance of the dentate region in the hippocampus and compare it to other areas of the hippocampus. It has been discovered that the dentate region sustains the most damage compared to any other region of the hippocampus in response to blunt force head trauma. Head injury affects millions of people around the world and can lead to neurological disorders such as epilepsy. Research has verified the mechanical nature of dentate injury by delivering trauma to both a live brain and a chemically fixed brain (a brain that has had all of its biological processes stopped). The cell damage patterns in and around the dentate from both cases are nearly identical, indicating that the injury to the dentate neurons progresses by mechanical means and does not involve a physiological process.
Researchers: Gloria Yang, Charlie Wen, Jacob Ceccarelli
Collaborator: Prof. Ivan Soltesz
Micro-Devices for Auditory Prosthesis Applications (Completed)
This project aims at developing (1) cochlear implants and (2) auditory neural implants. In the last decade, multi-channel cochlear implants have been demonstrated to provide auditory perception for profoundly deaf patients by electrically stimulating discrete populations of the auditory nerve fibers inside the cochlea via an electrode array. These current cochlear implants, however, do not reach the apical region of the cochlea, and thus fail to stimulate the nerves responsible for low-frequency perception. Further, patients with damaged cochlea cannot use these implants. The MEMS cochlear implant offers better contact between the electrodes and the target nerves inside the cochlea while reaching the apical region for better frequency coverage. The auditory neural implants will restore functional auditory perception to patients with damaged cochlea.
Researchers: Dhonam Pemba, Wyman Wong, Jian Wu
Collaborator: Prof. Fan-Gang Zeng
Mechanosensitivity in Hydra Stem Cells (Completed)
This project aims at studying the influence of externally applied stresses on the regenerative ability of hydra stem cells. Hydras are remarkable for their powers of regeneration. When a hydra is cut into fairly large pieces, each piece develops into a complete individual. Small pieces of hydra, when placed in contact with each other, grow together to form a complete individual. The simplicity and robustness of the regenerative ability in hydra provide a naturally elegant experimental tool to study stem cell differentiation. Hydra regeneration is easily observable under an optical microscope. The differentiation into either head or foot regions represents a simple "binary" system. Furthermore, its small size affords relatively simple experimental setups. In our studies, we pressurized hydra pieces under water over a period of one week, and observe and quantify the regenerative abilities.
Researchers: Phong Vuong
Collaborators: Prof. Hans Bode, Prof. Rob Steele
Publications: C046
Advanced Prosthetic Hand (Completed)
This project aims at developing several of the crucial components to enable an advanced prosthetic hand that mimic as closely as possible the degree-of-freedom, force, agility, and tactile sensing of a natural hand, with a direct interface with the nerous system of the user. We are part of the team responding to the “Revolutionizing Prosthetics” program at the Defense Advanced Research Projects Agency (DARPA). The vision of this program is to create a neurally controlled artificial limb that will restore full motor and sensory capability to upper extremity amputee patients. This revolutionary prosthesis will be controlled, feel, look and perform like the native limb. The over 200 amputees from current operations in Iraq and Afghanistan emphasize the urgent need to accelerate this progress with the goal of providing amputee soldiers with pre-injury levels of function and the ability to return to activities of their choice either within the Services or civilian society.
Researchers: Ryan A. Langan
Collaborators: Prof. Abraham P. Lee
Carbon Nanotubes as Resonant Devices (Completed)
This project aims at investigating the design, fabrication, and characterization of carbon nanotubes as resonant devices. In this work, we have developed the techniques to grow carbon nanotubes on silicon and quartz substrates, synthesized single-walled carbon nanotubes (SWCNT) up to 60 µm in length from lithographically defined catalyst sites, made DC electrical contact to nanotubes, measured DC depletion curve of SWCNTs at 4 K and room temperature, fabricated microstrip coupling circuit for nanotube S 11 measurements, performed initial nanotube impedance (S 11) measurements from 50 MHz – 20 GHz, and designed, fabricated, and characterized nanotube impedance matching circuit from discrete components. The encouraging findings from this project has led to a continuing efforts to expand CNT research in Prof. Burke's lab.
Collaborator: Prof. Peter J. Burke
Publications: C030, C031
Micro-Resonators for Wireless Communication Applications (Completed)
This project aims at developing micro resonators that operate at 50 MHz up to 1 GHz, with a Q of 1,000 to 10,000, using piezoelectric transducers on top of silicon resonant structures. Due to their small sizes, on-chip integration potential, and better performance, micromechanical resonators are attractive as replacements for the off-chip filters and oscillators currently used in communication systems. Significant process has been made in the last decade in this field, with high quality factors (>10,000) in GHz range. However, the impedance matching between the resonators and the associated signal pickup circuits remained unsolved, and the nanometerscale capacitive gap required by electrostatic-drive approaches posed a fabrication challenge. Further, these ultra-small resonators are characterized by very limited power-handling capabilities. We pursue the use of piezoelectric transduction with the objective of addressing all three challenges.
Collaborator: Prof. Eun Sok Kim
Publications: C029, C032, C033, C038, J011
Professor William C. Tang, Ph.D.