ANALYSIS OF 3D PRINTED METALS USING SMALL PUNCH TESTING
This work focuses on analyzing the fracture behaviors of 3D printed metals. Materials produced using additive manufacturing (AM), such as 3D printing, have varying strengths in different directions as a result of the layering process. To analyze how AM metals fracture, the metals will be deformed using a small punch test, which allows for the use of very small samples, while being scanned with a micro-CT. Since fractures in AM metals may form with fully internal voids and their behavior may depend on the manufacturing conditions, an x-ray is required to image the sample. The micro-CT will use x-rays to image the sample as it is deformed and use computed tomography to produce 3D images of the sample and its fractures, enabling the formations of fractures to be observed as they occur. This research is ongoing. Samples have been tested using a previous small punch test apparatus, which will serve as a baseline for testing materials to use in the final testing apparatus. A method to polish and prepare these samples by hand for testing was developed and refined. The design for the testing apparatus was developed and refined alongside material selection for dies. The materials will first be tested in simulation. The design for the testing apparatus has reached an acceptable version ready for prototyping.

Polystyrene Discs as Barriers for Diffusion in Layered Organogels

Transdermal drug delivery is a vital mechanism for skincare, hormone replacement, and other biomedical applications. Organic polymer gels have been recently identified as candidates for this drug delivery mechanism. Our present work focuses on controlling the direction of diffusion in a polymer gel with an organic network. Organogels contain a diffusion probe, tri-block copolymer, and an organic solvent. The tri-block copolymer forms a physically crosslinked network that consists of spherical polystyrene domains and a plasticized rubbery matrix consisting of ethylene-co-butylene and aliphatic mineral oil. The matrix phase is fluid-like and amenable to mass transport, which allows for probe diffusion. The main mechanism by which a probe maneuvers through a gel is time-dependent diffusion. Using Fourier Transform Infrared spectroscopy, the probe release rate can be tracked, and therefore, the fundamental parameter diffusivity can be determined. Controlling directionality allows for the delivery of probes to be tuned to our liking. Annealing external polystyrene was the main method employed to control diffusion. In particular, polystyrene pellets were annealed onto the face and walls of a gel. Sealed organogels were submerged in glass jars containing MO. Usually, gels submerged in MO gain in mass and thickness as a result of inward diffusion of oil into the gels. Our data shows that the mass transport of mid-block selective oil is limited based on how much Polystyrene covers the gel.

Metallic Plastics: The Effect of Electroplating on ABS Plastic

Experiments with post-processes and fabrication methods of 3D printed parts were explored, focusing on how to strengthen and aesthetically enhance acrylonitrile butadiene styrene (ABS) plastic. The main limitations of 3D printed parts being used for end products is the quality of their finish. A variety of post processing and finishing methods can be used on plastic parts in order to increase their material properties and aesthetics that would make them more appealing in the consumer world. However, some of these methods are time consuming and costly. In order to bypass these concerns, electroplating and electroless plating were tested. These are the process of coating one object with metal ions onto metallic paints and mixtures such as graphite, silver, nickel and copper, through chemical reactions to strengthen the base material. Comparisons between which metallic mixtures were best suited for each process, the highest yield strength, and the different processes themselves were explored. The experiment was conducted with ABS plastic dog bones as the base for the mixtures and coatings. Tensile testing on the finished, fully coated, specimens showed only slight differences in yield strength, about 0.5 – 0.7 MPa from the original, depending on the metallic base mixture and the plating process used, with the highest being the copper paint base, copper electroplated specimens. Despite the small changes in yield strengths, the specimens that were treated beforehand with prepping techniques such as degreasing and proper paint setting intervals, generated the best results in all mixtures and platings. 

Development of Origami-Inspired Geometric Models for Structural Applications
Determining the geometric and mechanical properties of origami-inspired folded systems for engineering applications is beneficial to identify and take advantage of their unique properties. Due to the construction of origami with stiff peaks and a folded nature, origami-inspired systems provide a rigid structure that is also compressible and deployable. These characteristics have been beneficial in various engineering fields, such as with solar power arrays, medical stents, and temporary shelters. Through this research, the Japanese Miura-Ori origami pattern has been determined to best align with structural engineering applications. Six versions of the Miura-Ori fold with varying angles and plate thicknesses were designed to enable 3D printing. The research process began with an exploration of the Miura-Ori pattern through paper and cardboard folded models. Through careful analysis, calculations were made to determine the geometry for models of varying angles and accounting for element thickness. Numerous extruding and layout techniques, as well as modeling software, were used to produce optimum model results with reduced structural weaknesses. Because of the uniquely thin elements and complex geometry of the Miura-Ori fold, the 3D printer properties were critical to avoid printing errors. After countless revisions, the Miura-Ori inspired models were successfully designed and 3D printed. Preliminary structural analysis was conducted to better understand plate buckling in SAP2000, a commercially available structural analysis program. The geometric modeling and 3D printing that was completed is the foundation of the current experimental testing and future computational analysis that will be used for verification of the experimental results.

A Microfluidic Biosensor to Detect a Specific Respiratory Pathogen

Micropillar array electrodes have many benefits, such as increased mass transport, lower detection limit, and potential to be miniaturized; hence, they play a crucial role in electrochemical biosensors. Geometrical parameters of micropillars (shape, height, etc.) affect the surface area of the electrode and improve the operation of biosensors. In this study, we investigated the effects of the different shapes of micropillars in a microfluidic biosensor on the response current by COMSOL Multiphysics. Finally, we designed a microfluidic biosensor consisting of micropillar array electrodes in order to detect a specific respiratory pathogen.

Title: Using Electrospray Technique to Fabricate Coatings that can Achieve Controlled Release

Abstract: The objective of our study is to use biodegradable materials to design coatings, via the electrospray technique, that can achieve controlled release. Controlled drug release is a beneficial and powerful tool to achieve reduced frequency of dosing, reduced side effects, and better control of drug concentrations in human bodies(Nokhdchi, 2012). These benefits result in an improvement in both the drug’s treatment effect and patients’ compliance with the treatment(Maderuelo et al. 2011). Additionally, using the electrospray technique, it is possible to fabricate polymer coatings on medical devices, such as stents, to be able to modulate their integration with surrounding tissues(Guo, 2015). There are many ways to manipulate a coating’s properties to achieve controlled release. In our study, we are interested in how the thickness of the coating will affect the release profile of the drug. Rhodamine B(a pink dye) is used to simulate the drug, and PVAc(a biodegradable polymer) is used as the polymer substrate of the coating. Coatings were made with different thicknesses, and the Scanning Electron Microscope(SEM) is used to measure the thickness of the coating. The desired coating, resulting from a successful electrospray experiment, has a shiny, smooth surface with a dark pink color. The SEM is used to examine the coating’s surface. After the coatings are made, a diffusion study is conducted by putting the coatings into the PBS solution. The dye releases over time into the solution, and absorbance values are measured regularly using UV Spectrometry and are converted to cumulative percent release. In the end, a percent release versus time graph is plotted for each thickness.

Characterizing Muscle Fatigue with Topological Data Analysis

Half of stroke survivors require long-term rehabilitative care, which is often complicated by a high degree of deficit variability. One debilitating effect of a stroke is muscle fatigue caused by muscle weakness. Identifying fatigued muscles can allow for targeted treatment plans and quicker rehabilitation; however, such a strategy has been hampered by difficulties in accurately characterizing fatigue.

Various linear and nonlinear signal processing methods have been used to characterize muscle fatigue from surface electromyography (sEMG) data, but they only characterize the frequency domain. Efforts to capitalize on the topological properties of sEMG, which include frequency and amplitude information, are in their incipient stages.

My research explores using topological data analysis as a robust measure of muscle fatigue. I constructed a custom device that stabilizes the hand and processed the data using a frequency-based Fourier transform. Leveraging techniques from Chutani, my team and I extracted a topological property (number of simplices) from the raw sEMG data. I compared the results of the two analyses and determined that the number of simplices is a more accurate indicator of fatigue than the traditional process, laying the framework for a new method of fatigue detection that could have meaningful implications for rehabilitation and sports sciences.

Title: Modeling the Effects of Femoral Anteversion and Miserable Malalignment on the Hip

Introduction: Excessive pathological torsion of the lower limbs can cause gait impairment, joint pain, and in extreme cases is treated with surgery. These torsional profiles can present in conditions such as high, femoral anteversion and miserable malalignment. Motion analysis and musculoskeletal modeling enable the analysis of
human movement to determine joint loads. Thus, the goal of this project was to use musculoskeletal modeling to determine the impact of varying degrees of femoral anteversion and miserable malalignment on the joint loads of the hip.
Materials and Methods: To begin the modeling process, the Rajagopal full body model and freely available experimental data were used as baselines. The Modenese bone deformation tool was then applied through MATLAB and OpenSim to alter the geometry of the baseline model and create one set of models with increased femoral anteversion and one set of models with miserable malalignment. OpenSim Moco –an optimal control
tool- was used to generate kinematics with actuator driven tracking problems and hip joint loads with muscle driven inverse problems. The simulations tracked the force throughout the stance phase of gait, by determining the root mean square (RMS) value of the joint loads.
Results and Discussion: The results of the simulations showed an increase in hip joint loads in both femoral anteversion and miserable malalignment models in the anterior-posterior and superior-inferior plane directions. Hip joint load increases were larger for models with increased femoral anteversion only in comparison to models with miserable malalignment.

Solid-State Shear Pulverization (SSSP):
An Investigation into Thermoplastic Types and Properties

Solid-state shear pulverization (SSSP) is an alternative polymer processing technique based on twin screw extrusion with a continuous cooling system. In SSSP, low temperature- mechanochemistry modifies the macromolecular architecture and morphology, which in turn leads to physical property changes in the material. While a wide range of homopolymers, polymer blends, and polymer (nano)composites have been previously developed with SSSP, fundamental understanding of how the mechanochemistry affects polymer chain architecture and structure, and in turn, material properties, have not been elucidated. This paper conducts a systematic, processing-structure-property relationship investigation of ten thermoplastic polymers with varying properties, as they are subjected to consistent SSSP mechanochemical pulverization and nanocomposite compounding. Structural, mechanical, and thermal characteristics of the neat polymers are correlated to their response to SSSP, by way of process covariants. Further, the multiple processing SSSP parameters dictate structural changes such as molecular weight reduction and filler dispersion level, which in turn dictate system properties like melt viscosity and thermal stability.

Design and fabrication of a caterpillar-inspired soft robot by 3D print method
Soft crawling robots can potentially access locations that are unreachable by humans and traditional rigid robots. And their delicate body parts prevent them from damaging the environment and themselves when falling. In this case, the soft crawling robots play a crucial role in conducting the missions like observing, monitoring, and even rescuing. During the summer, we developed a soft robot inspired by the crawling mechanisms used by the caterpillars. The robot is constructed by 3D printed parts and actuated by motors and strings attached to it. The uniformity between each segment makes modifying and manufacturing the robot easy. And its simple structure provides it the feasibility to adapt to and move in the complex 3D environment. Experimental results show that the 3D print soft parts can store and release elastic energy, and the designed structure allows the robot to mimic the motion of the caterpillars.