## Reference
### Design of Wireless Interrogated MEMS Capacitive Intraocular Pressure Sensors  
[PERSON] and [PERSON]  
Department of Electrical Engineering, University of South Florida, Tampa, FL 33612, USA  
Glaucoma is one of the main causes of blindness worldwide and it is irreversible. Even though surgery is deemed as the most popular treatment, it is also considered as a temporary solution with a risk of scar tissue buildup that increases the intraocular pressure (IOP). Thus, there is great need for constant monitoring of the IOP as the long-term increase of IOP can damage the optic nerve. In this work, a wirelessly interrogated MEMS based capacitive pressure sensor will be designed and implemented to monitor the intraocular pressure. The proposed pressure sensor consists of a varying-gap capacitor that will monitor the changes in capacitance as a function of pressure, which is integrated with a fixed inductor to create a mutual coupling between the implantable IOP sensor and the external readout unit. The pressure-induced capacitance variation will result in resonant frequency drift of the LC tank circuit, which can be used to monitor the inner eye pressure in a real time and continuous fashion with detection range of 0.1 mmHg to 60 mmHg. By using a finite element method (FEM) tool (CoventorWare), a MEMS capacitor model is built with strategically designed membrane sizes and material properties. After initial design optimization, electroplated nickel will be employed as the material for the suspended electrode along with a chosen membrane size of \(400\times 400\times 2.5\)\(\upmu\)m and a MEMS capacitive transducer air gap of 2 \(\upmu\)m. Furthermore, the equipment circuit model of a co-fabricated on-chip inductor is incorporated to form the battery-less LC tank circuit, which will be coupled with a set of external inductor coil as its readout circuit in an advanced design system (ADS). Meanwhile, a bench-top prototype system based on the same LC resonant coupling concept will be implemented to evaluate the optimal readout scheme between amplitude and phase of the resonant responses. Design, Fabrication, and Characterization of Capacitive MEMS Acoustic Emission Sensors for Nondestructive Testing (NDT)  
[PERSON], [PERSON] and [PERSON]  
Department of Electrical Engineering, University of South Florida, Tampa, FL 33612, USA  
The key function of capacitive MEMS acoustic emission (AE) sensors is to detect AE events due to structural degradation from solid structures in a real time and nondestructive fashion. The AE events are triggered by the structural damages in a solid structure to launch elastic waves. The MEMS AE sensor is designed as a mass-spring-damper system, where the diaphragm of AE sensors is supported by folded springs. In this work, CoventorWare is chosen as the finite element method (FEM) tool to design the capacitively-transduced MEMS AE sensors. The nickel plating and surface micromachining are the techniques to fabricate the MEMS AE sensors. The gap herein is 1.7 um and top electrode is 10 um. The resonance frequency of a MEMS AE sensor is set by the top electrode thickness and spring stiffness. Figure 2 shows the constituent unit cell of a MEMS AE sensor, which consists of a \(18\times 18\) array of the unit cells. By changing the folded MEMS spring geometries, the resonance frequency can be tailored. The employment of a large-scale array cells that individually produce motional current enlarge the overall output current signal. The MEMS AE sensors herein are based on capacitive or electrostatic transduction, where a DC bias voltage is applied between the fixed bottom electrode and the top movable electrodes to generate a motional current as a function of the velocity of the top electrode. The top electrode is driven into motion by the incident acoustic emission to generate a time varying motional current for the sensor to detect the AE events. The highest sensitivity of the capacitive MEMS AE sensors is obtained at the resonance frequency with a DC bias voltage near pull-in voltage.