Publications

Influence of Capacitive Transducer Nonlinearities on the Amplitude Limiting of MEMS Based Oscillators

Sherwin A. Afshar
Clark T.-C. Nguyen
2022

Microelectromechanical system (MEMS) based oscillators have become systems requiring high-performing references with minimal power consumption. The combination of higher quality factor and low parasitic capacitances allows them to out typical quartz crystal oscillators, capable of working at higher crucial for RF perform frequencies while providing excellent frequency stability with little power consumption. μ Previous work in [1] has demonstrated a 61 MHz oscillator meeting the GSM phase noise specification while consuming less than 80 W of power. More recent work in [2] demonstrates a...

Suppression of Oscillator Bias Voltage Phase Noise via MEMS Resonator Arraying

Jeffrey Ni
Clark T.-C. Nguyen
2022

Microelectromechanical system (MEMS)-based oscillators are in the heart of many of our electronic devices today, forming the timing basis for our increasingly higher frequency circuits. High-performance, low-noise oscillators are critical to meeting the standards of today's communication protocols. Effects of noise from all inputs of a circuit to the final output spectrum should be understood to make better oscillators, and this report specifically considers the effects of noise on the bias voltage supply needed for strong electromechanical coupling to sustain resonance. We investigate how...

Single-Chip Micro Mote in EEG, fMRI, and TMS Systems

Joshua Alexander
Kristofer S.J. Pister
2022

The goal of this project is to measure EEG signals in an MRI during TMS and report the EEG measurements wirelessly. The opportunities combining SoC-based devices with cutting-edge technology are rapidly expanding. A Single Chip Micro-Mote (SCμM) that has been developed as an ultra-small crystal-free SoC opens up the door of possibilities even more. Similarly, brain stimulation and measurement has taken a leap forward as Transcranial Magnetic Stimulation (TMS), Electroencephelography (EEG), and functional Magnetic Resonance Imaging (fMRI) have grown in popularity. A structure that...

Reticular Metalation in Metal-Organic Frameworks for Nanocasting and Interface Construction

Xiang Gao
Roya Maboudian
2019
Metalorganic frameworks (MOFs) are a class of porous, crystalline materials constructed by extending the linkages between inorganic and organic molecular building blocks through strong bonds. Because of their high porosities, accessible interconnected pore structures, and designable backbones, MOFs have been used in applications ranging from as catalystsupports, membrane substrates, sensing layers, and casting templatesf...

MEMS-Actuated Carbon Fibers

Rachel Zoll
Kristofer S.J. Pister
2019

This thesis presents a MEMS actuator capable of extruding or pulling itself along a sub-10μm diameter carbon fiber. The compact silicon microfabricated MEMS actuator can extrude fibers over many millimeters of distance with micron-level precision and is powered externally via high-voltage control signals.

One specific application demonstrated in this work is the insertion of microelectrodes for cortical neural recording. Microwire and microelectrode arrays used for cortical neural...

Electronic Interfaces for Bacteria-Based Biosensing

Tom Zajdel
Michel M. Maharbiz
2018

Bacterial sensing systems have evolved to detect complex biomolecules, operating near fundamental physical limits for biosensing. No modern engineered biosensor has managed to match the efficiency of bacterial systems, which optimize for each sensing application under constraints on response time and sensitivity. An emerging approach to address this short fallis to build biosensors that electronically couple microbes and devices to combine the sensing capabilities of bacteria with the communication and data processing...

The Ionocraft: Flying Microrobots With No Moving Parts

Daniel Drew
Kristofer S.J. Pister
2018
Enabling a future full of insect-scale robots will require progress on a huge number of fronts, one of which is the development of mobility platforms designed to operate beyond the scaling frontier of commercially available solutions. The vast majority of researchers seeking to create functional centimeter-scale flying robots have turned towards biomimeticpropulsion mechanisms, specifically flapping wings. In this work I take a very different tack, investigating a propulsion mechanism with no natural analogue —...

Silicon Carbide Bipolar Junction Transistors for High Temperature Sensing Applications

Nuo Zhang
Albert P. Pisano
Tsu-Jae King Liu
Liwei Lin
2014

An integrated sensing module capable of operating at high temperatures would be beneficial to a number of industrial applications, such as automotive industries, aerospace systems, industrial turbines and deep-well drilling telemetric systems. Consider industrial turbines as an example. It is important to monitor a variety of physical parameters within the hot sections of the turbines in order to increase turbine efficiency, reliability and to reduce pollution. In addition, real-time monitoring can help to detect and predict the failures of critical components in a timely fashion to...

Dopant Profiling of III-V Nanostructures for Electronic Applications

Alexandra Ford
Yuri Suzuki
Junqiao Wu
Ali Javey
2011

High electron mobility III-V compound semiconductors such as indium arsenide (InAs) are promising candidates for future active channel materials of electron devices to further enhance device performance. In particular, compound semiconductors heterogeneously integrated on Si substrates have been studied, combining the high mobility of III-V semiconductors and the well-established, low cost processing of Si technology. However, one of the primary challenges of III-V device fabrication is controllable, post-growth dopant profiling. Here InAs nanowires and ultrathin layers (nanoribbons...

Device Physics and Material Properties of Two-Dimensional Semiconductors

Sujay Desai
Ali Javey
Junqiao Wu
Tsu-Jae King Liu
Jeffrey Bokor
2018

Device architecture and materials innovations have enabled transistor scaling for the last several decades, boosting the performance of electronics, increasing the speed of communication and computational systems, lowering power consumption and reducing costs per operation. Two-dimensional (2D) materials have gained tremendous attention in the last decade, after the discovery of graphene which has exceptional properties like high carrier mobility, ultra-thin van der Waals connected layers (~ 0.3 nm thick), high tensile strength, etc.

Transition metal...