The Precision Instrumentation Group is focused on building the next generation of systems to advance metrology and manufacturing. The research in this group is highly multidisciplinary with students from Mechanical Engineering, Optics, and Electrical & Computer Engineering.
Research Project #1: Optical Probes for Measuring Freeform Optics
Freeform optics can expand the optical design workspace by allowing for more complex optical systems with a smaller package and decreased numbers of optical elements. Optical design software packages are beginning to incorporate tools to more effectively design these systems and advances in sub-aperture manufacturing have made the manufacture of these components possible. There is just one catch: there are no tools that can measure these optics with the desired accuracy to ensure they are manufactured properly and meet specification. The goal of this research project is to design, build, and test a prototype optical probe that can measure freeform optics when used with a 5-axis coordinate measuring machine.
Research Project #2: High Power, High Frequency Stability HeNe Lasers
Multi-axis displacement interferometry systems are widely used in complex manufacturing systems like lithography tools and semiconductor inspection equipment. As more fiber-based systems are used, the amount of available optical power becomes an issue. The goal of this research is to use a novel 3-mode stabilization technique to achieve better frequency stability (<1 part in 1010) while maintaining >3 mW of output power. One part of this research is to build a system capable of demonstrating this stabilization technique, which will entail a combination of optical alignment, mechanical design, and some controls. Additionally, the underlying theory as to why this technique works is not well understood nor is the stability limit known. Models will be developed to better understand the locking methodology and the mechanical requirements for the cavity stability to be better than <1 part in 1010.
Research Project: Fluid Mechanics of the Cochlea
(Joint project with Prof. Jong-Hoon Nam)
Motivation: Two Chamber Model of the Cochlea Supervised by Profs. Gracewski and Nam Motivation: The mammalian cochlea is a frequency analyzer. External sound stimuli are encoded at different locations along the cochlear coil (35 mm in human cochlea) according to their frequency. The human ear can resolve 3.6 Hz in the frequency range between 1000 and 2000 Hz. Without such remarkable resolution, we could not distinguish our friends’ voices over the phone. Interaction between the fluid in the cochlear duct and the basilar and tectorial membranes is believed to be responsible for the tonotopy—the relation between the frequency and the location of maximum basilar membrane response. Most current models of the fluid-membrane interaction model the basilar and tectorial membrane as a single structure. However there is experimental evidence that these membranes move independently, often oscillating out of phase. Therefore, the goal of this project is to develop a two-chamber model to investigate whether the independent motion has a significant effect on the frequency tuning.
Project Description: A former Xerox Fellow developed one-chamber time and frequency domain models of the cochlear duct and basilar membrane within the cochlea. These models will be generalized to two-chambers models that account for the independent motion of the tectorial and basilar membranes. The effects of the relative stiffnesses on the frequency response of the system will be investigated. In these models, the basilar and tectorial membrane will be modeled by a series of unconnected springs with varying stiffness. If time allows, these passive springs will be replaced with active, connected components that should predict higher local sensitivity to frequency.
Research Project #1: Measurement of Mechanical Properties of the Cochlear Partition
We study the mechano-transduction of the inner ear. The cochlea, the mammalian hearing organ, turns mechanical stimuli (sound) into neural signals. The identification of mechanical properties of cochlear sensory cells and tissues is crucial to better understand how we hear (or fail to hear). To measure the mechanical properties, we need to apply calibrated forces in the order of nanonewtons and measure displacements in nanometers at the speed of up to tens of kHz. Students will help with calibrating/developing force application methods such as acoustic sound pressure delivery to a micro-chamber system and magnetic tweezers (electro-magnetic force application through a micro bead). Through this project, students will experience how the principles of acoustics, electromagnetics, solid mechanics and vibrations are applied to micro-mechanical experiments with biological tissues.
Research Project #2: Different Modes of Propagating Waves in the Cochlea
(Joint project with Prof. Sheryl M. Gracewski)
The cochlea is an acoustic prism--it extracts different frequency components from sounds. The physical principle underlying this frequency analysis is mechanical resonance. The cochlear duct is a long tube filled with ionic solution and its cross-section is partitioned by two elastic membranes. As sound pressure is delivered to the cochlear duct through the ossicles (middle ear bones), the pressurized fluid field interacts with the elastic cochlear partitions to create propagating waves along the membrane. This finding of cochlear propagating wave gave the Nobel Prize to von Bekesy in 1961, and it was theoretically explained in the early 1970s. However, recently there were several observations that cannot be fully explained with the existing single-layer travelling wave theory. Students will help us explore different modes of propagating waves in the cochlear duct. Through this, students will experience how fundamental vibrations and fluid mechanics principles are applied to an intriguing biomechanical subject.
Research Project: Computational Solid and Structural Mechanics and in the Development of Engineering Practices in Antiquity
My research and teaching interests are in computational solid and structural mechanics and in the development of engineering practices in antiquity. Current research projects open to undergraduate students are in the structural analysis of monumental concrete domes and vaults from Roman Imperial architecture (1st to 4th century A.D.)
Engineering undergraduates participating in this research are trained in the application of 3D finite element stress analysis, a fundamental modeling technique widely used for research and product development in many areas of modern engineering. They also participate in the development of augmented reality visualization procedures for the display of finite element results on complex 3D models. Specific objectives are: to determine the structural behavior, the design philosophy, the construction process, and the process of structural decay for several major monuments, including the Great Hall of Trajan’s Markets, the Frigidarium of the Baths of Caracalla and Diocletian, and the Pantheon.
The investigation is based on systematic 3D computational modeling and stress analysis of the structural skeleton of each monument and involves creating detailed solid modeling reconstructions on which static and dynamic finite element analysis is performed to simulate gravitational and seismic loading conditions. This research is highly interdisciplinary: my students and I work with colleagues in archaeology, architecture and optical engineering, and with curators of monuments in Rome.
Research Project: The Role of Mechanical Activation in Power Production within Batteries
It is well known that chemical energy (from making and breaking bonds) is far larger than the energies associated with mechanical systems such as springs, gravity, and kinetic energy of objects. Thus, during energy conversion from chemical to electrical energy, (what goes on in batteries) it may be appropriate to use mechanical energy to change the kinetics of the chemical mechanism since the energy cost associated with the mechanical action will be small compared to the energy available from the chemical processes. This would allow batteries to put out power much faster but would require a small cost in terms of the total power created from the chemical energy stored in the battery. Heating a battery also causes increases in chemical reaction rates but the energy cost of raising the temperature can consume a large fraction of the energy stored in the system.
This project is to create a demonstration cell that shows that mechanical processes in an aqueous battery can be used to increase the rate of power generation, even if the total power generated is reduced. A typical copper zinc cell will be constructed with the capability of stirring of the cell to overcome concentration polarizations during discharge and further, the copper zinc cell will allow for mechanical abrasion of the active surfaces in order to remove or rearrange protective films that may be limiting the reaction kinetics. In effect, the exchange currents will be modified mechanically.
The results obtained will be used to determine the direction of the project aimed at documenting the effects of mechanical activation of chemical reactions, perhaps, by extending the experiments to include piezoelectric vibrational activation (ultrasonic activation) of the surface processes.