Exploring and Developing Tools for Autonomous Surface Vehicles
Computer Science, University of Maryland, Baltimore County
Advisor: Ani Hsieh
Mentor: Torrie Edwards
Autonomous Surface Vehicles (ASVs) that operate in field experiments require tools to help understand, manage, and develop the hardware and software. Building these resources requires expertise in many areas of engineering including: electrical engineering, computer science, mechanical engineering, physics, and mathematics. This project explores a wide range of software and hardware tools utilized in deploying ASVs. The software tools explored aim to design} different behaviors for both miniature surface vehicles (mASVs) and a larger Unmanned surface vehicle (USV). Behaviors are any set of instructions given to a robot for it to perform. Two behaviors are studied: one for the mASV to interact with objects, and one to allow the larger USV to explore real-world environments. Simulation serves as a visualization tool and a test environment where behaviors can be examined and analyzed before the experiment is conducted on the actual robots. Physical experiments are then performed to verify the performance of behaviors on hardware. In order to run experiments, it was necessary to develop control and hardware for the robots, including designing and fabricating a printed circuit board (PCB).
Design of a Passive Thermal Switch with Coupled Bi-Material Triangle Structures
Diego Barrutia Alta
Physics and Astronomy, Vassar College; Thayer School of Engineering, Dartmouth College
Advisor: Jennifer Lukes
Current reported thermal switches use positive thermal expansion and bimaterial structures to achieve an OFF/ON state. By contrast, here, we design a multimaterial metastructure that incorporates coupled tailorable thermal expansion. That is a wide range of positive and negative values of thermal expansion from coupled structures. By being able to behave as a conductor (ON) and insulator (OFF) at two distinct temperatures, the thermal switch is beneficial in a variety of thermal management applications, including optimized thermal insulation and self cooling to prevent overheating in electronics and batteries. To achieve this, the thermal switch needs to realize a multi functional structure having both sizable thermal expansion and high thermal conductivity. Analytical expressions for the coefficient thermal expansion (CTE) are theoretically established and numerically simulated for the structure’s combinations of positive and negative CTEs pairs. Moreover, finite element-based simulations are made to determine thermal deformation and heat transport of the metastructure. Using a two-step design approach, we first focus on the selection of the multiple materials and then structural modification of the mesostructures to provide a robust method for the design of a passive thermal switch with bi-material triangle inspired structure. To simultaneously obtain specific thermal switch states and thermal conductivity, design parameters should be selected with the consideration of the material thermal properties and thermal structural modification. The metastructure design has potential as a passive thermal switch allowing for a large thermal expansion and a small thermal resistance. With a systematic approach, this work demonstrates that ultimaterial metastructure can be potentially used as a tool of thermal transport.
A Tube with Thermally Removable Barrier for Single Tube, Two-Stage Polymerase Amplification
Electrical Engineering, Johns Hopkins University
Advisor: Haim Bau
The Hepatitis C Virus (HCV) is one of the leading causes of chronic liver disease that is commonly spread by needle sharing. The current standard for diagnosing HCV comprises an initial screening for HCV antibodies and followed, when positive, by a nucleic acid amplification test designed to detect the presence of HCV RNA. However, this time-consuming and expensive method is something that developing countries with a higher prevalence of HCV cases are unable to afford and is susceptible to patients failing to follow up and receive treatment. As a result, the spread of the virus is not controlled. In this paper, we focus on an HCV detection apparatus and method that is rapid, inexpensive, and simple to perform – a few of the conditions for point-of-care (POC) diagnostics. We developed a new polymerase chain reaction tube combined with the utilization of a two-stage isothermal amplification process (comprised of loop-mediated isothermal amplification and recombinase polymerase amplification) that together create a suitable POC device to test for HCV. Detecting the amplified template HCV target using visual colorimetric detection, our device is biocompatible with the amplification processes and can accurately diagnose controlled samples. With a simple two-stage process contained in a single tube, our device is a feasible tool for POC diagnostics in developing countries for the detection of HCV.
Development of Hardware and Actuator Components for Modular Tetrahedral Truss Robots
Mechanical Engineering, Howard University
Advisor: Cynthia Sung
A modular robot connects a group of unit cells to create a moving robotic system. These robots often utilize the tetrahedral shape as a unit cell because of its ideal geometric abilities to distribute tension and stress isotropically. Recently, modular tetrahedron robotics actuate using variable geometry truss (VGT) or variable topology truss (VTT) which manipulate the edge length and topology of the tetrahedron unit cells. However, robots using VGT and VTT often experience actuation issues. Origami robotics address these limitations by using compliant joints to simulate similar movements achieved by VGT and VTT but bypass the actuation issues. Therefore, this proposal aims to explore origami robotics as a suitable alternative for VGT and VGT actuation. First, we aim to modify the Trussbot, a tetrahedron origami robot, to address the movement limitations that the Trussbot encountered in its prototype. The challenge is to create custom mounts for electronic components and manipulate a breakout board and pins that enable the Trussbot to execute its movements more fluidly. Three-dimensional modeling and printing streamlined the creation of the mounts. The breakout board was formalized using adobe illustrator and materialized via PCB circuit board, solder, and insulated wire. Second, we use the tetrahedron unit cell modules to explore a two-degree of freedom robotic arm option. The combined experiments and modifications explore the exciting possibilities of using tetrahedron unit cells in the ever-growing field of origami-modular robotics.
Effects of Polystyrene Coating on the Reflectance Spectra of Quasi-2D Hybrid Organic-Inorganic Perovskite Flakes
Electrical Engineering, Georgia Institute of Technology
Advisor: Deep Jariwala
Mentor: Surendra Anantharaman
Quasi-2D Hybrid Organic-Inorganic Perovskite (HOIP) flakes possess reflectance spectra characterized by peaks and crests, called “modes”, that vary in their width and height. The reflectance spectra of these flakes are very sensitive to changes in their environment in the sense that these modes will shift in their wavelength position along the electromagnetic spectrum, and also change in their intensity, in response to different materials (with different optical constants) being deposited or coated on top of these flakes. The motivation behind us studying these HOIP flakes is that their reflectance spectra could serve as a sensor, because a change in intensity (change in brightness) or shift in wavelength (change in color) of the modes of these spectra could indicate to a human observer that some change in the environment has occurred. However, a major drawback that makes HOIP flakes tricky to implement in most real-world applications is that they rapidly degrade when exposed to oxygen. In the interest of both using these HOIP flakes as a sensor and preventing these HOIP flakes from degrading in oxygen, we spin-coated perovskite flakes with various thicknesses of polystyrene and analyzed how the reflectance spectra changed in response to these polystyrene coatings, and also over the course of many days following the polystyrene coatings. We find that polystyrene coatings induce additional cavity modes to these spectra and also successfully protect these flakes from degrading in oxygen when compared to a control sample that did not receive any polystyrene coating.
Novel Soft Sensor Design in the Detection of Normal and Shear Forces
Mechanical Engineering, Stevens Institute of Technology
Advisor: Kevin Turner
Mentor: Christopher Stabile
In this study, we design and create a fabricating process for a contemporary piezoresistance force sensor sensitive to normal and shear forces based on previous research on this sensor type. Designs are compared and optimized using analysis tools on 3D modeling software where design decisions before being physically fabricated. The fabrication process employs liquid metal printing where conductive strain gauges of EGaIn are encapsulated in polyurethane to form a force sensor. Experiments with applied loads in normal and shear are then conducted to verify that the sensor is capable of distinguishing between the two forces, resistance changes possess linearity, and analyze properties such as the hysteresis of the sensor. The results show that a sensor based on our fabrication process and design decisions can theoretically create a sensor capable of shear and normal force detection.
A wireless, battery-free photoplethysmography-based implantable force sensor
Electrical Engineering, Cornell University
Advisor: Andrew Richardson
Tactile sensations play a critical role in guiding motor actions. However, several neurological diseases and injuries prevent this somatosensory information from reaching the brain, making coordinated movement difficult for many patients. To restore this crucial sense of touch in patients with nerve damage, we present a novel implantable photoplethysmography (PPG) -based sensor that measures changes in subcutaneous blood flow to infer forces applied to the skin. In this design, a photodiode amplifier circuit is used to detect changes in subdermal absorption of red and infrared light, and a monotonic relationship between the absorbed light and applied force was observed. The sensor receives power and transmits data wirelessly over a near-field communication link to a nearby base unit. The fabricated sensor occupies a footprint of 20.67 mm2.
Streamlining Magnetoelectric Magnetic Field Sensor Testing
Electrical Engineering, Northeastern University
Advisor: Troy Olsson
Magnetoelectric composite magnetic field sensors have recently shown promise for biomedical applications such as magnetoencephalogram, allowing for rapid room temperature neuroimaging. In this work, an AC magnetic field sensor testing structure is presented to easily perform electric, magnetic, and modulation tests on these devices. The testing structure provides a simple way to quickly characterize the performance of the piezoelectric layer, magnetostrictive layer, and the entire device. The design incorporates a wound electromagnet to provide a DC bias field for the magnetoelectric sensors and a PCB RF coil to reduce its volume and to create a detectable AC magnetic field. The design was 3D printed, providing a stable structure to test the devices on. The structure was designed for a modular setup, allowing different parts to be swapped in and out depending on the test performed and for any future components to be implemented. Further modifications to the structure utilizing the modular setup include a linear Hall effect sensor to precisely determine the DC magnetic field and a rail with adjustable permanent magnetics to allow for perpendicular magnetic field biasing of the sensors.
Molybdenum Coupled Electrochemical Sensing Systems
Chemical Engineering, University of Arkansas
Advisor: Mark Allen
Mentor: Elizabeth V. Schell
Abstract: To improve the efficiency of crop production, widespread agricultural monitoring of important nutrients and environmental factors must be explored. Electrochemical sensors have the ability to be compact and made of transient materials, making them a powerful tool for this purpose. This paper investigates the use of molybdenum as a phosphate sensor, by characterizing two modalities: amperometric with 3 electrodes and potentiometric with 2 electrodes. Mo was utilized as the working electrode in both instances, and tin and gold were used as counter and reference electrodes in the two- and three-electrode systems correspondingly. When open circuit potential (OCP) tests were run, there was no clear trend between voltage output and phosphate concentration, suggesting that this type of sensor will not be suitable. To test the possibility of an amperometric sensor, cyclic voltammetry (CV) and chronoamperometry tests were run, and both presented promising data. Furthermore, direct current values were correlated to varying phosphate concentrations, allowing a precedent to be set for the sensor. When the electrochemical cell was biased at 1.2 V, the sensitivity of current to phosphate concentration was found to be 0.8179 dec/dec over the range of 1E-1 M to 1E-4 M. Now that the feasibility of an environmentally benign phosphate sensor has been established, more research can be done in the packaging and construction of the sensor, to ensure its biodegradability and compactness.
Bioinspired Active Electrosensing System for Microscopic Robots
Electrical Engineering, Princeton University
Advisor: Mark Miskin
With a broad range of potential applications in medicine and industry, microscopic robots present the opportunity to engage with the microscopic world in an exciting new way. Current research efforts aim to incorporate on-board electronic circuits and improve actuator performance. In the quest to develop fully autonomous microrobots that are capable of more complex programmable tasks, an object detection methodology must be identified for the microrobots to sense and navigate their aqueous environment. Since at the microscale, underwater object detection technologies based on light and sound cannot be utilized, we propose a microscale object detection methodology inspired by the biological sensing modality of active electrolocation employed by some species of freshwater fish. We aimed to demonstrate the viability of developing an active electrosensing system for robots at the microscale. To accomplish this, we fabricated titanium/platinum microelectrode arrays to explore sourcing and measuring in a conductive solution and plan to implement a series of experiments quantifying the effect of factors such as the location and size of the occlusion on electric field strength in the solution.