MEMS Sensors

Inductively Coupled Flexural Wave Resonator Sensing

This collaborative work between Professor Todd Kaiser at Montana State University and Professors Jennifer English and David Coe at the University of Alabama in Huntsville uses frequency modulation spectroscopy to monitor the energy absorption of a flexural plate wave resonator. Electromagnetic energy is coupled into the microelectomechanical flexural plate wave resonator via an induction coil antenna and a comb capacitor that are microfabricated on the surface of a piezoelectric membrane. The piezoelectric membrane converts the electric fields in the capacitor into mechanical motion of the membrane. The maximum energy absorption occurs at the mechanical resonance of the flexural plate resonator driven by the electrical resonance of the inductor-capacitor circuit. The frequency of the maximum energy absorption is monitored very accurately by using frequency modulation spectroscopy. This mechanical resonant frequency is perturbed by agents that attach to the surface of the membrane. The flexural plate resonator is made into a sensor by incorporating binding sites on the surface of the membrane that are designed to couple with specific biological or chemical agents. 

MEMS Actuators

The quality of neural recordings in physiology is directly related to the positioning of electrodes used in experiments. Using static multi-electrode arrays can be a major problem since many electrodes are not optimally positioned and the acquired signal is contaminated by neighboring signals or in the worst case, no signal is present at all. Conventional solutions result in cumbersome and difficult to use movable electrode systems. What is needed is a microelectrode array that would allow electrodes to move independently, yet be spaced hundreds of microns apart. The objective of this research is to develop a micromechanical electrode array that has individual insertion depth control. Each individual electrode would be actuated independently, while monitoring neural stimulation or reception. The electrode would be inserted until a relatively strong signal is obtained. The depth of each electrode then could be optimized for peak performance of the array. The microelectromechanical system (MEMS) is produced using the backfilling of trenches etched in silicon substrates. This manufacturing method allows for mechanical-electrical isolation and uses batch fabrication to produce devices in linear arrays. The linear arrays would then be stacked to produce large two-dimensional arrays suitable for neural-microprocessor interfaces.

This figure shows the microelectrode with a flexible lead connection, reverse drive actuator, forward drive actuator and a clamping system. 

This figure shows a close up of the electrode and the drive and clamping shuttles. 

This figure shows a close up of the electrode tip.

trench 6

Close up of a cross section of the electrode. 


Close up of a pre-released electrode that has been cleaved. 


Close up of a pre-released electrode that has been cleaved. 


Released electrode tip with clamping pads. 

The same fabrication and actuation method can be used to produce a microstepper motor. 


Several new courses have been developed that use the Montana Microfabrication Facility. The processes and techniques used for producing the sensors and actuators are currently being developed and characterized.

Current Projects

Radiation Tolerant Computing - Position sensitive radiation sensor Fabrication