Research
Study of Beryllium Bearing Bulk Amorphous Metal (BAM) Composites – Brown University – 1999-2000 Supervised by Dr. Rodney Clifton. The facture response of a tungsten (80 wt %) / BAM (Be-Ni-Cu-Ti-Zn) (20 wt %) was studied under dynamic strain loading using a Kohlsky bar apparatus. ABAQUS simulations were completed to explain interesting fracture surface, which was completely normal to a planar impact of a free boundary surface.
Particle Image Velocimetry (PIV) as Diagnostic for a Novel Zinc-Air Fuel Cell – UC Berkeley 2000-2002 Supervised by Dr. James Evans. Full frame as well as spot PIV (using a boroscope) analysis was carried out on a moving bed of zinc-granules in air as well as water slurry. A stochastic model was implemented in MATLAB to build a correlation map in order for spot PIV to be used as a cost-effective diagnostic system for tracking granular flow in a novel zinc-air fuel cell.
Particle Image Velocimetry of Gas Stirred Vessel – UC Berkeley – 2000-2001 Supervised by Dr. Dipak Mazumdar and Dr. James Evens. Water models were built to simulate stirring conditions of steel processes. PIV was used to map the flow during start-up and relaxation transients as well as steady state flow. Correlations between flow rate, nozzle diameter, and extent of stirring were examined. Initial modeling of the system was carried out in FLUENT, though computational limitations prevented a proper three-dimensional study.
Survey of Micropower Sources for Wireless Sensor Networks, UC Berkeley, 2002-2003 Supervised by Dr. Shad Roundy. Examined alternative power sources for wireless sensor nodes. Well established power sources, such as batteries, were reviewed along with emerging technologies and currently untapped sources. Power sources were classified as energy reservoirs, power distribution methods, or power scavenging methods, which enable wireless nodes to be completely self-sustaining. Several sources capable of providing power on the order of 100 μW/cm3 for very long lifetimes are feasible. The major finding was that no single power source will suffice for all applications, and that the choice of a power source needs to be considered on an application-by-application basis.
Wireless Sensing of Aluminum Smelting Potlines, UC Berkeley, 2004 - Present Supervised by Dr. James Evans and Dr. Paul Wright. We a tested solution to accurately measure various process parameters via wireless sensing technology, specifically Berkeley motes running TinyOS, using the cells’ waste heat as a thermoelectric power source. Early experiments at Eastalco indicated that the motes, with a few modifications, would be able to operate reliably in industrial conditions, successfully transmitting radio packets, despite the plant’s strong magnetic fields, at distances of over 100 feet. This study describes the successful testing of wireless measurements of several cells’ parameters, and discusses what other measurements are feasible and appropriate, and describes the energy-scavenging thermoelectric power sources.
Fire Information and Rescue Equipment, UC Berkeley, 2002-Present Supervised by Dr. Paul Wright. To facilitate the design and development of an advanced IT network specifically for fire crews at the scene of an emergency, the Fire Information and Rescue Equipment (FIRE) team from UC Berkeley conducted interviews at the Chicago Fire Department Training Facility in December of 2002. The study was then broken into two parts. The first was to mine the information gained from the interviews directly, such as department practices and protocols, firefighter experiences with and expectations of communications technology, and fire command operations through the Incident Command System (ICS) to understand how current protocol could be enhanced by technologies, and what protocols needed modification to accept critical new technologies. The second half discusses how these results, along with other background studies, lead to a design of head of 1) head mounted display for firefighters as well as an infrastructure to gather and deliver information to firefighters, 2) modified smoke detectors with UC Berkeley motes that allow for the low cost monitoring of a fire scene in real time, and 3) a network two connect these two products seamlessly.
Development of a Small, Low Cost Wireless Galvanostat, UC Berkeley, 2005-Present Supervised by Dr. James Evans. Testing microbatteries requires microampere resolution current control capability in an inert atmosphere. Commercial systems capable of this cost at least $1000 for a single channel, and need to be routed through the glovebox physically. We have created an add-on circuit to a low cost wireless sensor node to achieve this functionality with no breaching of the glovebox required. It has a four accessible 12-bit analog to digital converters (ADCs) and two 12-bit digital to analog converters (DACs) as well as pulse width modulation (PWM) capability. The mote is programmed using TinyOS and nesC, open source software designed specifically for wireless sensor nodes. In addition to being economical, the transparency of the hardware and software allows for direct customization of hardware for specific purposes. We demonstrate a design that uses either PWM or DAC to set a current with microampere resolution for any value between -1 and 1 mA. An ADC measures the potential of the battery during charge cycles. A small foot print Java program controls the galvanostat and logs the ADC data.
Dispenser/Inkjet Printing of Lithium Ion Battery Electrodes, AIST Tsukuba Central, Japan, 2005 Supervised by Dr. Kazuhiro Murata. A four-axis stage was built and place inside of an inert atmosphere glovebox to allow the study how effectively electrodes of carbon and silver could be deposited and dried/sintered in successive process within the same atmosphere. Colloidal silver inks as well as silver nano-pastes were printed, as well MCMB carbon mixed with PVDF and NMP. Initial findings indicate that nano-pastes as well as sol-gel derived ink can be modified to work well with inkjet processes, but dispenser technology is better suited to conventional battery pastes. Subsequent studies will focus on cathodic materials as well as the effect of dispenser/inkjet printing parameters (viscosity of paste, writing speed, dispensing pressure etc.) on the final electrochemical behavior of the electrode.
Microbatteries for Wireless Sensor Networks, UC Berkeley, 2003-Present Low temperature screen-printing of novel electrode materials is explored to create microfabrication compatible thick-film microbatteries. A screen printing/stenciling process and a dispenser printing machine have been developed to create cells between 0.25 cm2 and 1 cm2 in area and 200µm to 300µm in thickness. The printing can done completely within a high purity argon glovebox at atmospheric pressure. Solution processing enables many different combinations of gels and pastes to be applied at ambient pressures and temperatures. Pastes of colloidal silver, MCMB/PVDF, MCMB/PEO, LiCoO2/PVDF, LiCoO2/PVDF and composite gels of V2O5/PEO and V2O5/PVDF are under consideration. We find that screen-printing yields good feature control, while stencil printing can be utilized to quickly lay down thick films with surface aliasing determined primarily by the nature of the paste applied. These devices are printed directly upon SiO2 and Si3N4 insulated wafers. A lithium-polymer-ion battery is simulated in DUALFOIL to optimize cell geometries for a few different smart dust applications that can be made with screen-printing technologies. As expected, current density and duty cycle have a large effect on the capacity achieved for a given discharge. The simulations indicate that our printing method, in conjunction with power management, should be able to meet the application parameters.