A SYSTEM FOR SIMULTANEOUS MEASUREMENT OF ABSORPTION AND ELECTROCHEMICAL REACTIONS

Advisors: Prof. Jorge Santiago-Aviles (EE) and Marcelo Fontes

Abstract: Nitric oxide is an extremely important molecule in biological systems. It is possibly one of the most important messenger molecules and has many other important roles in biological systems. Measurement of nitric oxide is very important. The overall project of this group of scientists is to design and create a sensitive and selective nitric oxide sensor. This paper deals with the portion of the project that focuses on making the sensor more sensistive using one of six different materials. In order to do this, a system will be created in which simultaneous measurement of absorption and electrochemical reactions (spectro-electrochemistry) will be possible.

REAL-TIME SPEECH RECOGNITION USING A NEURAL COMPUTER

Advisor: Prof. J. Van der Spiegel

Abstract: The overall project goal is to perform real-time speech recognition of continuous speech using an analog neural computer. This would validate the potential of the neural computer for speech recognition and add to the understanding in the field of neural computers. The neural computer is used in combination with hardware accessories to perform phoneme recognition and ultimately, speech recognition in real-time. In order to accomplish the task of phoneme recognition, some existing feature detectors will be modified to improve performance. The bulk of this paper deals with the design of the voicing detector. What is voicing and what is its value in phoneme recognition?

FABRICATION METHODS FOR THE PRODUCTION OF A TWO- ELECTRODE NITRIC OXIDE SENSOR

Advisors: Dr. Jorge Santiago-Aviles, Marcelo Bariatto Fontes, and Vladimir Domin ko

Abstract: As part of a long term project, a nitric oxide sensor was designed by Dr. Jorge Santiago-Aviles and Marcelo Fontes. Methods of production for this sensor were established and tested. The sensor was composed of arrays of six parallel microelectrodes and bonding pads on each surface of a double-side polished silicon wafer. Insulation between the microelectrodes was provided by a silicon dioxide layer; while the surface of the device was passivated with a polyimide layer. Windows were to be opened in the polyimide layer in order to expose the bonding pads and active surfaces of the electrodes. The material used for the active electrode was gold while the counter electrode was fabricated with an Ag/AgCl structure.

Silicon etching with potassium hydroxide combined with alignment utilizing an infrared camera was the technique used to align the top and bottom surfaces of the wafer. Due to their small physical size, etching of the microelectrode structures proved to be very difficult. It was hypothesized that regrowth of the oxide layer after the KOH etching would greatly enhance the mechanical stability of the transmission lines. Gold etching was successfully accomplished using a KI-I2 etch for one minute, followed by a 20 second immersion in 400 milliliters of a solution containing 30 grams of cetric ammonium nitrate, 7880 mL of deionized water, and 120 mL of nitric acid to remove the nichrome adhesion layer from the areas between the electrodes. A completely succesful etch of the silver was not accomplished due to a depletion of the silver available for electron beam deposition; but promising results were obtained via the use of a 500 thick aluminum mask and a 50 milliampere electrochemical etch, i.e. a reversed electrodeposition.

ULTRASONICALLY-ASSISTED MACROMOLECULAR CRYSTAL GROWTH

Advisors: Prof. H. Bau (MEAM), Prof. D. Voet (CHE), and Prof. N. Chandra

Abstract: In this project studied the effect of ultrasound on macromolecular crystal growth. Lysozyme crystals were grown under an ultrasonic field. The use of the ultrasonic waves under different frequency and voltage settings had different effects on the crystal growth process of the lysozyme. We used conditions that seemed to be beneficial for the process and conditions but instead of being beneficial, were harmful to the process. Through the use of ultrasound we observed some interesting effects that helped us grow large enough monocyrstals.

THE CHEMISTRY OF A NITRIC OXIDE SENSOR

Advisors: Dr. Jorge Santiago-Aviles and Marcelo Fontes

Abstract: An effective way to detect and measure nitric oxide has been extremely desired because of the recent discoveries of its vast importance in biological systems. A project to design a sensor that can directly detect nitric oxide in the nanomolar range has begun. This sensor will use amperometric techniques to measure the nitric oxide. This report focuses on the characterization of the working and reference electrodes used in the amperometric techniques. This research project also explores the chemistry of nitric oxide and its oxidized states, nitrite and nitrate, in order to have a better understanding of the reactivity and chemistry of the nitric oxide in its biological environment.

REAL-TIME TRACKING AND TARGET ACQUISITION WITH SILICON RETINA AND PC

Advisors: Dr. Ralph Etienne-Cummings, Dr. Jan Van der Spiegel, and Dr. Paul Mueller

Abstract: A tracking and target acquisition system was designed and implemented using a silicon retina, a 486 DX-2 PC, and a Servo Systems stepper motor. Because the silicon retina performs edge detection, logarithmic compression, and Difference-Of-Gaussians on the image plane, the tracking calculations may be performed on a relatively inexpensive PC. By dividing the image into two distinct regions, the periphery and fovea, the system was able to eliminate background noise, maintain a target in its central field of view, deal with occlusion, and detect and acquire new objects of interest. In addition, the system provided valuable insight into the future implementation of a similar tracking system that will use only a single VLSI chip. Finally, the tracking system was used to guide a remote control vehicle along a marked path.

MICROFABRICATION OF INFRARED WIRE GRID POLARIZERS

Advisor: Professor Nader Engheta

Abstract: Wire grid polarizers can be fabricated to work as polarizing filters in the near infrared and in the red regime of the electromagnetic spectrum. Theory, construction, and applications of these filters are explored, with one application being the integration of the polarization difference imaging system, introduced by Professors Nader Engheta and Ed Pugh at the University of Pennsylvania, onto a chip using wire grid polarizers and silicon photodiodes.

E.N.I.A.C. HARDWARE IMPLEMENTATION

Advisors: Prof. J. Van der Spiegel and Prof. F. Ketterer

Abstract: ENIAC was built 50 years ago to meet the needs of calculating fast and accurate firing tables during World War II. This was the first general purpose, all-electronic computer. Now, 50 years later, a group of students from the University of Pennsylvania have been given the task of reconstructing the ENIAC by the use of current CMOS technology, to learn how it worked, and to rebuild several components of the ENIAC in vacuum tube technology.

THERMAL EXPANSION MERCURY DRIVEN LIQUID SHEAR MONITOR

Advisor: Professor J. N. Zemel

Abstract: The operation of a thermally driven actuator and capacitive flowmeter was examined. The driver was emulated with a thermometer. The eventual goal of the project is to design a thermally actuated driver to move organic fluids through micro channels. Flow measurements for channels (hydraulic diameters ~ 2 – 40 µm ) were desired. Measurements of such small channels is a challenge. It was proposed to measure the flow rate by means of noting the change in capacitance of the modified thermometer. Initial tests verify that a thermometer as a driver is feasible. Further testing is required to measure flow rate accurately.