Current Research Projects
Tactile Micro-Sensors for Digital Tonometry of the Eye
This project is aimed at understanding the mechanical response of the human eye during digital palpation. The long term objective of the project is to develop non-invasive techniques for correlating its mechanical response to disease states such as elevated intraocular pressure and glaucoma.
3D Tactile Display for the Education of Blind Persons
This project aims to provide three dimentional graphics access to blind persons by utilizing a wearable device that works in real time as response to human finger's movement. Electromagnetic microactuator is designed in this work to produce tactile coninuity illusion such that the fingertip receives continuous stimulation as a virtually presented sense of touch. By setting up our high speed magnetic position detection system, the location of the finger and actuator can be tracked in realy time by order of milisecond updation rate. The close loop control interacted between computer and human is realized to form a final three dimensional object during this virtual 'touching' process.
Drug Delivery Micro-Robots
This project investigates the use of ultrasonics and magnetics as potential drug release mechanisms in biomedical micro-robots. With advancing technology in the steering and guiding of these robots, controlled actuation has become an important area of research. Encapsulating these robots in a micro-scale droplet has allowed us to increase the amount of drug delivered by each robot. Using our innovative extrusion system we are working to improve the repeatability and efficiency of such micro-robots and their actuation.
Research in Micro/Nano Education: Low-Cost MEMS/Micromechatronics Laboratory for Undergraduate Students
Multi-Axis Temperature Compensated Force Sensor for Microassembly
This project has developed one of the basic building blocks in the pursuit of force feedback microassembly systems, the force sensor. The sensor is silicon based and micromachined using standard fabrication processes with an inepxensive three mask procedure. The sensor can measure three independent force components with a 20 microNewton resolution utilizing piezoresistive Wheatstone bridges on a thin diaphragm. Tracking errors due to the difference in temperature coefficients between the bridge resistors are compensated through the use of an innovative annular resistor. The annular resistor is insensitive to stress but remains sensitive to minute temperature fluctuations, allowing for the high resolution of the force components.
Past Projects
Electrostatic MEMS for Optical Micro-Assembly
Production of complex miniature devices often requires assembly of components with sizes ranging from several microns to a few hundreds of microns. When applied to the micro scale, the conventional assembly techniques often result in an uncontrolled gripping and release or have insufficient gripping force. Further, vacuum and mechanical chucks obstruct the field of view and are thus incompatible with automatic vision feedback systems. To overcome these limitations, the development of a micro-gripping technology with integrated optical alignment capabilities based on a transparent electrostatic micro-gripper is proposed. The optical transparency of this device will allow pick and place operations to be performed using computer controlled visual alignment.
Molecular Nanoassembly
This project is aimed at exploring a combination of the top-down and bottom-up approaches for the purpose of ‚proving a concept for manufacturing nano-scale molecular structures. First, target sites for molecular assembly are defined (top-down phase), followed by molecular self-assembly onto these sites (bottom-up phase). The target sites consist of locally injected charge using a technique known as charge writing with SPM probes. Molecules with charged ends of opposite nature can thereafter be held to these sites by electrostatic attraction. The benefits of such binding over the chemical methods would be the non-destructive release of the temporarily bound molecules, as well as the ability to scale up the process using focused ion beam writing.
Thermal Micro-Actuators for Micro-Relays
Thermal micro-actuators are a promising solution to the need for large-displacement, low-power MEMS actuators. Potential applications of these devices are micro-relays, tunable impedance RF networks, and miniature medical instrumentation. The first thermal actuators developed for such applications were made through thin film deposition of poly-crystalline silicon, which is brittle and has limited displacement-force characteristics. The aim of this project is to develop low-cost metal actuators on both traditional silicon substrates as well as non-traditional flex-PCB substrates. The fabrication technique is based on electro deposition of Ni, Cu and other metals in photo-lithographically defined trenches.
Eletroactive Polymer Actuators
Polymer-Metal composite actuators represent a novel application of ion exchange polymers. Research on these membranes over the past 30 years has focused on their chemical properties and their application in separation columns, water hydrolyzers, and fuel cells. It is only very recently that researchers proposed their use as actuators. Despite their simple geometry, the governing mechanisms of deformation of the composite are quite complex. Electrochemical studies on Nafion and similar membranes have shown that water transport is actually responsible for their swelling. The electroactive polymer actuators consist of ion exchange membrane covered with conductive layer.