Maxwell Kerber

Fabrication and Analysis of a MEMS NIR Fabry–Pérot Interferometer

We report the design and fabrication of a tunable MEMS Fabry-Pérot étalon for use in microscale spectroscopic applications. The reflective elements of the interferometer are dielectric mirror stacks optimized for 1500-nm light and the tunability arises via capacitive attraction of a translatable mirror on a spring. The mirror reflectivity was measured to be 97.3%, corresponding to a calculated finesse of 115, while the measured linewidth and FSR are 70 cm-1 and 334 cm-1, respectively, corresponding to a measured finesse of 5.

Underwater wireless power transfer for maritime applications

This paper presents the development and implementation of an inductive, underwater wireless power transfer system for use with unmanned underwater vehicles (UUVs). Specifically, the design and fabrication of power transfer coils and power electronics is provided for a system capable of providing 75W to a load. At small standoff distances (<;2 inches) and frequencies below 300kHz, it is shown that there is little difference between inductive power transfer in air and seawater. Measured data shows that at power levels of 75W, the system efficiency from the transmitter to a rectifier and resistive load is above 85%.

Optimization of kinetic energy harvester for low amplitude vibration

This paper presents the steps involved in optimizing the design of an electromagnetic kinetic energy harvester (KEH). The KEH device is conceptually a highly non-linear device. There are numerous dependent variables involved in the design of a KEH which are reliant upon the specific environmental conditions in which the KEH will be deployed. Furthermore, the non-linear nature of the device leads to an iterative design process. The environment that the KEH is deployed into also dictates the overall design and power per volume achieved by the device.

Thermal and biofouling effects on underwater wireless power transfer

This paper presents a characterization of the thermal effects and marine fouling on an undersea wireless power transfer system. The coils used in wireless power transfer experience elevated temperatures due to the resistive losses in the wire. Several different coating strategies to both protect the coils against seawater and dissipate the generated heat are investigated. In addition, the rise in temperature can increase the likelihood of marine bio-fouling on the exposed surfaces of the coils. A study of bio-fouling on the wireless power transfer coils and whether there might be increased microbial growth as a result of the power transfer is also explored.

Development of kinetic energy harvesting systems for vehicle applications

This work demonstrates the implementation of a functional kinetic energy harvester designed to power wireless sensor electronics used in vehicular applications. The design, fabrication, and experimental characterization of a complete electrodynamic (magnetic) energy harvesting system capable of delivering in excess of 10 mW from 100 milli-gs of acceleration is presented. Unlike previous energy harvesting research, which typically focuses on individual components for proof-of-concept testing, the system implemented for this work includes the integration of a low-frequency transducer, power electronics circuitry, and a rechargeable storage element, all of which are required for a functional system. The design trade-offs, which result from the integration of these system components are examined and design rules for maximizing efficiency are given. Finally, field testing is presented, which demonstrates the ability of the system to operate over a range of different vehicle speeds.

Design and analysis of a novel electro-optical MEMS gyroscope for navigation applications

A novel gyroscope design is presented that has potential to reach navigation-grade performance, i.e. bias instability < 0.01 °/hr and Angle Random Walk (ARW) < 0.001 °/√hr. The design is based on the incorporation of an optical transduction mechanism used to decouple drive and sense signals, a dual crystalline silicon spring fabrication approach along with a large drive mass and small sense mass to enhance Coriolis displacement.

Powering of wireless sensors through the exclusive use of kinetic energy

This paper demonstrates the powering of wireless sensor nodes with the exclusive use of a novel kinetic energy harvester (KEH). This KEH is designed to operate under low accelerations which are practical to find in a typical environment where a sensor would be deployed. Four different sensor types were powered with accelerations ranging between 17–300mg.

Design considerations for an active rectifier circuit for bidirectional wireless power transfer

The capability of bi-directional, underwater power transfer (both sending and receiving power) increases the functionality of underwater vehicles by allowing them to be charged and provide charge wirelessly to other systems without leaving the water. To minimize the footprint of the charging circuitry, a single transistor-based full-bridge circuit can be used to either send or receive power. This work focuses on the operation of the circuit in power receive mode, as an active rectifier. An algorithm common for active rectification is presented, and the effects of non-idealities on the timing control and efficiency is presented through experimental results.

Harmonic analysis with a MEMS-based Raman spectrometer

This paper discusses the incorporation of a novel method of signal processing with a MEMS Raman-based chemical/biological sensor. The method utilizes an absolute sum-difference calculation performed on the FFT of a periodic Raman signal that will be obtained from the MEMS sensor. The result of the sum-difference calculation is used in a threshold determination of the presence of an analyte of interest.

Design of highly reflective subwavelength diffraction gratings for use in a tunable spectrometer

The design of highly reflective subwavelength gratings (SWGs) for use in a micro-electromechanical system (MEMS) tunable spectrometer is presented. The SWGs are designed to be polarization independent at an incident wavelength of 1.5 µm with high reflectivity over a 200 nm bandwidth. Two designs are considered; Model 1: a silicon layer with periodic air holes and Model 2: a stacked Si-SiO2-Si design with the last Si layer a periodic array of columns. The designs are simulated using a commercial rigorous coupled wave analysis (RCWA) software package. The RCWA software aids in the design of SWGs that have higher reflectance than traditional dielectric mirrors. Model 1 has a reflectance (R)≫0.99 for lambda 1.37–1.6 µm. Model 2 has a R≫0.99 for lambda 1.46–1.69 µm. Finally, both designs are modeled to create a Fabry-Perot cavity, and at an incident wavelength 1.5 µm, the designs have a reflection finesse of 1707 and 4452 for Model 1 and Model 2, respectively.