Jing Wang

Date of Award

Spring 2003

Document Type


Degree Name

Doctor of Philosophy (PhD)


Micro and Nanoscale Systems

First Advisor

Tranhong Cui


Recent development in microfabrication technology has brought much attention to the development of miniaturized, inexpensive and high-accuracy MEMS devices and microsystems. The ultimate goal of our project is to develop a versatile, three-dimensional, high precision sensor platform, which can be used for displacement, velocity or acceleration measurement. The first step, on which this dissertation is based, is to fabricate a one-dimensional (parallel with the Z axis) tunneling sensor, which in turn can be developed into two- and three-dimensional sensor platforms through structural and functional integration.

Since the invention of mini-structured high-sensitivity silicon-based tunneling sensor in 1993, the synthesis and fabrication of PMMA-based tunneling sensors still remains an over-looked area. Compared with traditional silicon-based tunneling sensors, PMMA is less expensive, has little stiffness, and is easier to work with micro-machining process. Moreover, this all-PMMA-based tunneling sensor is one of the first generations of functional micro-sensors/devices for organic compatible applications.

The hot embossing technique, one of the most widely used micromachining approaches in “soft-lithography”, was chosen for its fast turnaround, fewer processing parameters, and simplicity. Because the mold can be used repeatedly, the potential of mass-production is further highlighted in this dissertation.

All-PMMA-based tunneling vertical sensors have been successfully fabricated. The overall size of the packaged sensor is 8 mm x 8 mm x 1 mm, with the measurement circuits bounded together. The natural frequency of the sensor structure is 133 Hz. The bandwidth of the feedback system is 6.3 kHz with voltage over acceleration sensitivity of 20.6 V/g. The resolution at 192 Hz is 0.2485 μg/[special characters omitted].

Compared with the silicon-based tunneling sensor, the PMMA sensor's apparent advantages are: low cost, less processing time, less processing instruments, high yields, wider bandwidth, and theoretically lower noise level. Given all our research results, we can expect that the PMMA-based tunneling sensor platform to become the base for the next generation of highly sensitive micro-sensors in many important areas, notably in chemical, magnetic, infrared, and organic applications.