Human-machine interfaces, which map signals measured from a user into inputs for a device, hold promise to allow efficient and individualized device usage, whether for rehabilitation or recreation. Surface electromyography (sEMG) can non-invasively measure muscle activity through the skin to provide many potential user inputs to control a computer. Despite sEMG’s promise for user-controlled programs, clinical and commercial success has been low, in part due to poor user training regimens. sEMG-based interfaces are often unintuitive to learn, and not all motions will contribute equally to control, due to inherent limitations in electrode placement and sensitivity. Training users by presenting them with visual feedback of which actions can contribute to the task may enhance learning by discouraging strategies using undetectable motions. Thus, I propose training users to learn an adaptive decoder using an sEMG radar plot which displays real-time visualizations of the user’s sEMG signals, with each channel arranged in a circle such that motions appear as unique conformations of the radar. I hypothesize that showing users the radar plot before completing a sEMG-controlled computer task will confer greater task success. To test this, I conducted a set of experiments with adult subjects using the radar plot as brief, pre-task training for a two-dimensional, cursor-control game, comparing user performance between those trained and untrained. I anticipate that users who received radar plot training will demonstrate faster task learning and lower tracking error. Such a result would shed new light on how to streamline sEMG-based interface training, and may encourage further modifications or improvements of the radar plot. Optimizing the human-machine interface training process will be integral to their path to clinical and commercial success.

The application of engineered origami structures has become increasingly popular for the past decades. Among the variety of origami patterns, the Resch pattern recently began to reveal its potential in the field. It is a planar tessellation composed of pre-defined polygons. Some of its interesting properties feature controllable morphability and self-supporting reformability. However, its static and dynamic response to an external load remains to be unveiled. Therefore, this project aims at studying the Resch-patterned origami structure’s folding behavior, associated stored potential energy, and impact mitigation capability. We first constructed its kinematic model in order to accurately predict the folding motion of a tessellation. The model was then augmented with a torsional spring embedded in each crease line to predict the force-displacement relationship under external loads. We fabricated a series of prototypes with polymers and conducted static compression tests to compare and calibrate the kinematic model. The force-displacement curve generated from the kinematic model was fitted to the experimental result, that the two curves shared a very similar profile. As for the physical model, it demonstrated consistent force-displacement and energy dissipation properties over cyclic compression-expansion tests. After studying the fundamental behavior of the Resch pattern, we performed dynamic impact tests on our physical model to explore its potential for impact mitigation. A cylindrical weight was dropped on the center of our Resch pattern at its natural posture, and by tracking the motion of the impactor, we determined the energy and momentum dispersed in the impact. In summary, the Resch-patterned origami structure’s unique properties exhibit great potential for impact-mitigating structures for deployable panels with repeated loads. We envision that the energy handling mechanism of the Resch pattern investigated herein can be employed in numerous engineering structures, including lightweight deployable architecture.

Thin film photovoltaics (PV) present many advantages which enable their potential replacement of traditional silicon PV, but they are not yet scalable. Current research aims to enable their large-scale production to meet growing energy demands. Alongside scalable manufacturing methods and competitive device lifetimes, the transition from small-area cells to large-area modules poses a scalability barrier. I explore a novel fabrication method accelerating this transition. In fabricating thin film PV modules, large-area films are divided into multiple small-area cells by removing, or “scribing,” thin films between adjacent cells for later electrical connection. Existing scribing methods include laser and mechanical scribing, but both have drawbacks which impede device performance and scalability. My research professor and I invented a third scribing method to address these issues. Lines of solvent are printed onto a thin film device to dissolve target thin films underneath the solvent. As the solution evaporates, the “coffee-stain effect” redistributes the dissolved material to the fluid perimeter, exposing linear areas of underlying thin films. This effect is characteristic of drying liquids containing dispersed solids: liquid from the interior flows to restore liquid evaporating at the edge, carrying nearly all dispersed material to the fluid perimeter. This effect enables thin film scribing without forming performance-inhibiting film defects or toxic residues. The technology also requires low capital expenditure and is compatible with scalable roll-to-roll manufacturing. In this work, I demonstrate the invention’s feasibility and competitiveness by producing scribes comparable with existing technologies using electrohydrodynamic inkjet (EHDIJ) printing of solvent on perovskite solar cells. I authored a report, filed a provisional patent application, and now collaborate with another university to advance the technology. This invention poses a scalable solution to the transition from small-area cells to large-area modules in the thin film PV space, breaking a pivotal barrier to meeting growing energy demands.

The aerospace industry frequently requires mechanics to inspect confined airplane wing tanks for prolonged periods, putting them at risk of ergonomic and chronic strain injuries. We propose an easily deployable tool for inspecting airplane wing tanks without entering the confined space. Our lightweight four degree of freedom robotic arm combined with an immersive virtual reality (VR) experience will simplify and speed up the inspection process while reducing ergonomic risks for mechanics. A cascading rail provides up to a five foot reach while maintaining compact design, and actuators allow maneuverability between pipes and access to hard-to-see regions, with panning, tilting, rotation, and camera (end-effector) tilt. A 360 camera placed at the end of the system provides detailed images from inside the tank. To make the VR experience immersive, we propose mapping images onto a known computer-aided design (CAD) model, allowing the mechanics to inspect different parts of the 3D tank model inside VR while having the actual image of the wing tank superimposed on the 3D model. Additionally, we propose a 3D map constructed with several 360 images for the tank that allows the mechanics to navigate the tank using selected waypoints. Mechanics can click desired inspection positions on the 3D wing map to display a view of the selected location, providing seamless inspection. Our research has the potential to improve confined space inspection by increasing efficiency and reducing health risks for mechanics.

Over the last decade, the electrohydrodynamic (EHD) interaction produced by dielectric barrier discharge (DBD) actuators has seen strong interest for active flow control applications. Plasma synthetic-jet actuators (PSJAs) are DBD jets capable of producing zero-net mass flux momentum injection through ionic interactions in air at atmospheric pressure. These devices are of particular interest due to their rapid response time, lack of moving parts, variety of tunable parameters, and repeatably demonstrated efficacy in boundary layer modulation under a range of flow conditions. Due to the edge-normal momentum injection characteristics of PSJAs, previous studies naturally focused on surface wall jet configurations with spanwise cartesian geometries (see straight-edge, serrated, fingered electrodes) in quiescent, co-, counter-, and cross flow external conditions. We present an alternative 2-dimensional polar axisymmetric geometry; a circular ground electrode that is concentric and equal in diameter to the inner edge of an active high-voltage electrode ring. Steady-state inward injection develops an inward impinging jet and a resulting wall-normal net momentum directed away from the surface. A thorough electro-mechanical characterization led to the development of an empirical model of axisymmetric wall-normal plasma synthetic-jet actuators. The actuators utilize 0.0625” quartz glass as the dielectric material and have critical diameters of Dg = 40 mm, 60 mm, and 80 mm with an active electrode ring thickness of 10mm. The actuators are tested over an AC current operating range of Vpp = 8 – 60kV and f = 0.5 – 8 kHz. Direct thrust measurements are taken at all electrical conditions and intermittently validated through pitot-tube flow-profile tests. This provides rapid insight into the voltage-frequency-diameter-thrust relationships for axisymmetric PSJAs as well as finer intricacies, including entrainment patterns, high-Reynolds eddy formation, and jet dissipation. Combined with electrical current analysis, the axisymmetric PSJA is found to be an effective method of producing wall-normal momentum-injection. This research will directly contribute to the furthering of electric propulsion and flow control systems, opening the doors to more capable, more efficient, and greener flight technology.

In this research project, our multidisciplinary team is developing environmental forensic technology to identify illegally caught seafood, with a focus on high-value species such as bluefin tuna. To tackle the difficult task of immediately detecting illegal, unregulated, and unreported (IUU) fishing, we are developing a rapid, affordable, and portable detection device that uses isothermal amplification and blue LEDs to detect resultant green fluorescent products indicating the presence of tuna DNA. As the lead Electrical Engineer, I designed an electrical circuit to precisely and stably control the temperature of a resistive heater using a microcontroller, thermistor, and PID algorithm along with an LED circuit. The requirement for the process involves the utilization of isothermal amplification technique at a fixed temperature of 37°C (33-42°C range) and green fluorescence detection (at 550 nm) in DNA using blue LEDs (at 470 nm) and an orange acrylic filter to filter the blue wavelength. The result is a circuit that meets the requirements for the biochemical process and enables real-time feedback without the need for shipping samples to a laboratory. With the development of the device finished, the next step is to streamline the user experience. I am leading the software development effort to create a phone application that facilitates the assay setup process and automates image capturing and analysis. With a capable research team, including colleagues shaping the user interface, a junior researcher connecting the device to the phone application, and a Ph.D. candidate in Computer Science and Engineering developing a proprietary camera software, our team's effort culminates in a user-friendly phone app that streamlines the assay workflow and provides real-time sample analysis. With the completion of this project, we will be able to make a difference by helping communities and marine ecosystems.

In the era of Internet of Things, the operation of various kinds of sensors or devices on the shelves in warehouses or supermarkets often requires batteries or complex wire management. To address this issue, we propose a charging solution utilizing the near-field wireless power transfer (WPT) with multiple relay resonators, also known as a multi-hop WPT system. In this study, we designed and simulated several coil geometries for the WPT system to ensure high efficient power can be delivered from a transmitter to a receiver through various coil hopping configurations. After evaluating the trade-off between the coupling coefficient of coils in parallel and series as well as the design complexities, we constructed many unified coils in one geometry. We then measured the coil-to-coil estimated efficiency using the scattering parameter obtained through a Vector Network Analyzer on a foam board shelf. Our results show the efficiency range from 9% to 81% in the worst and best hopping configurations, respectively. Furthermore, we proposed a power efficiency optimization approach to improve the worst hopping configuration by up to 80%. We anticipate that the success of this work will significantly reduce the staff cost associated with the maintenance of wire management and charging systems on each shelf. It will also simplify the assembly process and enhance the accessibility of smart shelves while potentially mitigating environmental impact by reducing battery usage.