Reena Dahle

Enhanced bandwidth microstrip patch antennas through 3-D printing

A novel approach for realizing improved-bandwidth microstrip patch antennas (MPAs) with use of 3-D printed Acrylonitrile Butadiene Styrene (ABS) substrates is presented. By 3-D printing these substrates using the MakerBot Replicator 2X, complex cavity-backed MPA designs typically implemented with subtractive manufacturing techniques such as micromachining are easily adapted without loss of efficacy. In order to improve the structural robustness of the MPA and substrate, several different cavity structures are implemented and tested. Introduction of the air cavity into the synthetic substrate improved the bandwidth by up to 90%. Antenna gain was also improved by 1.2dB for some designs. This simple and cost-effective approach can be used for multiple applications to enhance and incorporate multiple cavities and varying geometries into a synthetic substrate resulting in varying dielectric properties.

A simple sensing mechanism for wireless, passive pressure sensors

We have developed a simple wireless pressure sensor that consists of only three electrically isolated components. Two conductive spirals are separated by a closed cell foam that deforms when exposed to changing pressures. This deformation changes the capacitance and thus the resonant frequency of the sensors. Prototype sensors were submerged and wirelessly interrogated while being exposed to physiologically relevant pressures from 10 to 130 mmHg. Sensors consistently exhibited a sensitivity of 4.35 kHz/mmHg which is sufficient for resolving physiologically relevant pressure changes in vivo. These simple sensors have the potential for in vivo pressure sensing.We have developed a simple wireless pressure sensor that consists of only three electrically isolated components. Two conductive spirals are separated by a closed cell foam that deforms when exposed to changing pressures. This deformation changes the capacitance and thus the resonant frequency of the sensors. Prototype sensors were submerged and wirelessly interrogated while being exposed to physiologically relevant pressures from 10 to 130 mmHg. Sensors consistently exhibited a sensitivity of 4.35 kHz/mmHg which is sufficient for resolving physiologically relevant pressure changes in vivo. These simple sensors have the potential for in vivo pressure sensing.

Reducing the effect of parasitic capacitance on implantable passive resonant sensors

Passive, LC resonators have the potential to serve as small, robust, low cost, implantable sensors to wirelessly monitor implants following orthopedic surgery. One significant barrier to using LC sensors is the influence on the sensors resonance of the surrounding conductive high permittivity media in vivo. The surrounding media can detune the resonant frequency of the LC sensor resulting in a bias. To mitigate the effects of the surrounding media, we added a “capping layer” to LC sensors to isolate them from the surrounding media. Several capping materials and thicknesses were tested to determine effectiveness at reducing the sensors interaction with the surrounding media. Results show that a 1 mm glass capping layer on the outer surfaces of the sensor was sufficient to reduce the effects of the media on sensor signal to less than 1%.

A compact and high quality factor Archimedean coil geometry for wireless power transfer

A compact, magnetically coupled wireless power transfer (MC-WPT) planar Archimedean coil (PAC) geometry is presented. This PAC geometry combines conventional planar aligned and anti-aligned coils in a single Archimedean layout, resulting in a quality factor (Q) twice that of a conventional coil. The PAC WPT system demonstrates a measured power transfer efficiency (PTE) that is improved from 15% to 35%. Moreover, with the use of the Archimedean coil geometry, the WPT system exhibits a higher PTE over a wider range of frequencies. This compact PAC geometry is 10% smaller in size than its conventional counterparts, and maintains a larger PTE with lateral coil misalignment.

3-D Printing as an Effective Educational Tool for MEMS Design and Fabrication

This paper presents a series of course modules developed as a high-impact and cost-effective learning tool for modeling and simulating the microfabrication process and design of microelectromechanical systems (MEMS) devices using three-dimensional (3-D) printing. Microfabrication technology is an established fabrication technique for small and high-precision MEMS devices; these processes typically take place in a cleanroom with the use of expensive high-vacuum equipment. These course modules were developed to provide engineering educators a more affordable and effective method for teaching MEMS modeling in settings without a cleanroom, as is the case in many undergraduate institutions. Feedback from student evaluations as well as course grades all support the efficacy of these course modules. In these hands-on modules, by designing and building the MEMS prototypes, the students learn by experiencing the process of building a MEMS device from the specifications given. The results are also compared to similar assessments made in the course before the introduction of these course modules to verify success. The detailed description of the modules, the evaluation methodologies adopted, and reflections on the implementation are discussed.