It is projected that in 40 years, 3.6 million individuals in the U.S. will have a limb loss and approximately 40% of them are major lower-limb amputees. Lower-limb prosthesis is needed to regain the mobility in these amputees. Many implications have been made in prosthetic feet to improve the mobility of the amputees, yet seldom investigations have done on the design of the pylon to improve the same function. This project is to design a novel elastic pylon fitted with a rigid foot to have the same, if not better, functionality to a rigid pylon with a high performance prosthetic foot. Due to the expensive cost and the limitation of the prosthetic feet, the design of elastic pylon is needed to reduce the cost of the overall prosthesis and find alternative ways to improve the mobility. The elastic pylon was modeled first using a finite element analysis program. Then, the modeled elastic pylon was manufactured, fitted with a rigid foot and compared to the rigid pylon with the high performance foot on bench testing. Ultimately, the elastic pylon will be tested on the amputees for gait analysis and the kinematics of the amputees during walking in both rigid pylon-high performance foot and elastic pylon-rigid foot and compared. The success of this project would result in a reduced cost in the prosthesis, as well as alternative ways to improve the mobility of the lower-limb amputees.

When cells migrate, they undergo a complex process of signaling pathways coordination and interaction with their surrounding environment. Actin filaments polymerize at the leading edge of the cell membrane, pushing it forward and allowing for the cell to bind to new sites in the extracellular matrix. In order to sophisticatedly study the process of cell migration, one must pay close attention to the initial binding points, or nascent adhesions, that can either fall apart early and cause the front of the cell to collapse, or grow into the larger focal adhesions that provide the mechanical support for the cell in the extracellular matrix. Though tools have been created to study the mechanics of cell forces, there is a distinct lack of ability to measure the extremely small forces created by cells, such as the contraction of a single filopodia. This work serves to develop such a tool, in the form of polydimethylsiloxane (PDMS) nanopost arrays, via soft lithography manufacturing techniques. These nanoposts can be treated as tiny cantilever beams by which deflection can be immediately translated to force, using known dimensional and material properties of the posts. Fabrication of the posts consists of a single-cast of PDMS onto silicon negative molds and curing the posts at 110° C at low vacuum pressure. It has been determined that vacuum pressure is necessary to achieve the maximum post aspect ratio, due to surface tension issues between the liquid PDMS and the silicon chip. The gas permeability of PDMS allows for the air contained in the holes of the master chip to escape and be replaced by liquid PDMS while curing. The success rate of nanopost fabrication is characterized by relating post aspect ratios to vacuum pressure of the curing environment, which are found to correlate.

The mission of the Cell Biomechanics Lab led by Professor Nathan Sniadecki is to “understand how mechanics affects human biology and disease at the fundamental level of biological cells.” To do this, microstructures are created in this lab to interact with cells on their native micrometer length scales. These microstructures, made out of polydimethylsiloxane (PDMS), take the shape of micropost arrays on which cells are placed. When the cells attach to the posts they exert forces which bend the microposts. This bending is measured and used to calculate the forces generated by individual cells. It is important to measure these forces to fundamentally understand cell interactions within living tissue. This research increases the sensitivity and function of micropost arrays by decreasing the diameter (thus reducing the stiffness) of the posts to the nanometer scale using PDMS etchant, tetrabutylammonium fluoride (TBAF). With nanometer diameters, researchers gain the ability to measure forces produced by individual filopodia. Difficulties with this approach include ensuring homogenous etching of the arrays, and controlling the etch rate. This research overcomes both of these difficulties. To ensure a homogenous etch, the etchant is circulated evenly among the posts using a flow chamber. Etching rate is controlled by adjusting the etchant flow rate and time. Experiments are currently in progress. So far, etch rates have been determined for different flow rates using single block and post structures. This knowledge has been used to design the micropost array experiments. These experiments will be conducted in the coming weeks.

The National Cancer Institute estimated that there will be approximately 72,570 new cases of bladder cancer in the United States during the year 2013, and 15,210 deaths due to the disease. The high recurrence rate of 50-70% of treated bladder cancer creates a necessity for life long surveillance, which in turn makes bladder cancer the most expensive cancer for a per-patient cost—89,000 to 202,000 USD per patient—from diagnosis to death. This research aims to combine the cancer specific biomarker 5-Aminolevulinic acid (5-ALA) and the Scanning Fiber Endoscope (SFE) to fluorescently detect and treat cancerous legions in a controlled setting within the bladder, and to find any correlations that might exist between our dependent and independent variables, allowing us to optimize cell death. The Scanning Fiber Endoscope (SFE) created in the Human Photonics Lab (HPL) at the University of Washington was used to apply therapy at 405 nm to A549 cancerous cells previously administered with 5-ALA. Cells were stained with LIVE/DEAD® stain and analyzed under a confocal microscope. The results show that PDT of A549 cancer cells with 405nm light and 5-ALA induces Protoporphyrin IX (PpIX) was successful. Varying sizes in cell death were produced when varying combinations of duration of therapy and light intensity were applied. A correlation between light intensity and duration of therapy was found. An increased time of exposure and a decreased light intensity yields a larger area of cell death than a decreased time of exposure and an increased light intensity. Recurrence of cancers is mediated by cancerous cells that are overlooked in the treatment process, therefor optimizing cell death will allow for a decrease in costs associated with bladder cancer due to a decrease in recurrence rate.

A stepper system is a device that uses multiple small-scale steps to achieve large ranges of motion. There are several fields where stepper systems can be used as positioners such as micro/nano-fabrication, scanning probe microscopy, and alignment of optical components. This stepper design enables a motion stage, whose motion is generated by friction induced with piezoelectric actuators underneath, to move horizontally without vertical displacement. The objective of this research is to investigate a way to support the load of a motion stage while limiting any restriction of motion in the horizontal direction. This restriction of vertical load bearing and horizontal freedom has led to investigating bearings as a component of the support structure. There are many types of bearing designs (i.e. ball, magnetic, and air) that may satisfy the design constraints, so I have performed analysis on various types of bearings and investigated their impact on the design of a new stepper system. For instance, ball bearings support radial loads or thrust loads with forces normal to the ring pathways, but continuous compression, along with expansion, leads to fatigue of the rings, which shortens their lifetime; while magnetic bearings provide support with a distance force that is controlled by the current flow in the circuit, maintaining a more stable and friction-free motion. However, applications may be sensitive to magnetic interference and therefore magnetic bearings may not be suitable for use in some cases. Taking into consideration the benefits and limitations of the different bearing systems, my research has proposed and introduced the design of a stepper support system.

Current estimates place pancreatic adenocarcinoma within the top ten deadliest diagnosed cancers in the US and #1 for mortality (~98%, five years after diagnosis). Consequently, early detection and the study of its pathology are paramount. Typically, this is accomplished through microscopy of flat specimens that are taken from tissue core (TC) biopsies (d=400-1200 µm) of a patient's pancreas. In the Human Photonics Laboratory, we are attempting to enhance diagnostic sensitivity by using a 3D microscopy system, originally designed for single cells, to image entire 400 μm diameter TCs. Imaging thick, opaque TCs requires specimens to be optically cleared and stained. Therefore a microfluidic device (MD) was developed to prepare pancreas (pTCs) and agarose hydrogel (aTCs) cores in an "all-in-one" approach that simplifies, automates and preserves the 3D structure of TCs. Flow and diffusion properties for bulk tissue in MDs deviate from the well-characterized properties of single cells. Subsequently, designing the initial MD required investigating histological dye diffusion and fluid flow with TCs. We found transparent 1% agarose were a suitable pancreas substitute for observation/measurement of volumetric diffusion in an open chamber. In comparison, pTCs needed to be cut open for subsequent analysis. Initial results demonstrate that by 30 min, most dyes completely diffused through larger (L=10 mm, d=2 mm) aTCs, but concentration profiles between dyes varied. Although the density and stiffness of aTCs matched pTCs, diffusion differed, as dye in pancreas samples diffused only 12% as far as in agarose. Properties of dye diffusion into aTCs with flow were then studied on a smaller scale in a test microfluidic channel (L=5.2 cm, d=720 µm). A slow flow rate of 80 µL/s was created by a variable-height gravity line system. Initial results demonstrate that slow flow rates significantly attenuated dye diffusion into aTCs, but allowed the aTCs to remain stationary.

With efforts being made to remove human impact on the ecosystems surrounding us, underwater ambient noise is a topic of interest. Understanding and even mitigating this ambient noise has come to be of foremost importance in various fields. To understand underwater noise, it is best to first have a well-developed understanding of noise in general and what it is about noise that we should concern ourselves with. Starting first with sources of sound, such as that of a person singing, can provide an introduction into how to process sound measurements underwater. By working with recordings in “.wav” form I was able to convert to a spectrum, or spread of frequencies, that can be read in terms of the frequency and underwater pressure, two important aspects when studying underwater ambient noise. Using a numerical computation language (GNU Octave) to analyze sound data, I was then able to see plots of these spectra as well as to generate Pressure Spectral Density plots. I was then provided guidance regarding how to interpret these plots and apply this knowledge to various locations, a necessary introductory step in the overall process. Understanding ambient noise in general, as I was able to start doing this summer, and then taking it further to understand ambient noise in our area, is the first step towards curbing disturbances to our marine ecosystems.

Barrett’s Esophagus (BE) is an inflammation of the lower esophagus. This inflammation can progress to cancer through a stage called High Grade Dysplasia (HGD). One approach to early detection of HGD is the use of light emitting “beacons “consisting of fluorescently labeled peptides targeted to HGD tissue biomarkers. Our laser based Scanning Fiber Endoscope (SFE) possesses the ability to capture live images of the esophagus during examinations and also excite and locate fluorescently tagged targets. Refining SFE fluorescence imaging for clinical use requires mathematical algorithms such as image stitching and distance compensation. Image stitching combines a series of partial views of a 3-D surface into a composite view of the entire surface. Distance compensation addresses the issue of fluorescence signal reduction as the distance between the light emitting beacon and endoscope increases. Phantoms are synthetic mimics of disease conditions used to refine and calibrate new medical devices. This research was directed toward the development of a low-cost, flexible, and durable esophagus phantom with color matching to provide a realistic model of BE. The color of inflamed BE tissue and healthy tissue were matched using quantitative combinations of commercial acrylic paints to create recipes for both tissue types. The resulting paint mixtures were applied to the interior of a latex cast cylinder mimicking the dimensions of an adult esophagus. The painted latex models were shown to a panel of gastroenterologists for approval. The end result was the development of a color realistic phantom onto which fluorescent targets could be affixed. The phantom was imaged using the SFE and demonstrates 2D stitching with distance compensation. (C. Yang, V. Hou, L. Nelson, E. Seibel. J. Biomed. Optics, Feb 2013) Future work extends similar techniques to develop brain tissue phantoms for the calibration of the SFE after integration onto the RAVEN surgical robot.

Multi-Legged terrestrial biological systems demonstrate complex forms of locomotion by utilizing different gait patterns and leg motions for different environmental conditions. Typically, the footpath of biological systems consists of a smooth flat region when the foot is in contact with the ground where the forward motion of the body occurs. The following research focuses on designing a mechanical linkage-based leg mechanism to effectively mimic the step of a biological system. A simulation of the linkage was performed using MATLAB in order to analyze the dynamics of the foot path and duration of stepping phase that the foot was in contact with the ground. After analyzing the foot motion, the linkage-based leg designs were then constructed using the LEGO Mindstorms NXT robotics kit and tested with various walking patterns. Further analysis of the linkage-based leg motion was done by comparing the resulting motion to biological leg motion; successful linkage-based leg designs should display similar stepping characteristics to the biological motion.

Heart disease and stroke are the first and third leading causes of death for men and women in the U.S. and together account for more than a third of all U.S. deaths. It has been shown there is a correlation between decreased intercellular forces in the endothelial cells in the artery and higher permeability of the arterial lining. This can lead to atherosclerosis, a disease defined by hardening of the arteries, a major underlying cause of heart attacks and strokes. The focus of this research was to determine how different blood flow rates affect the intercellular forces of the endothelial cells that line the arterial wall. The first step was to fabricate microposts. Negative molds of the posts were cast off of a master array of microposts for which the spacing, height and diameter of the microposts were known. A positive mold was then cast off of the negative mold to produce a substrate on which the cells could be cultured. Next a flow chamber was designed for these experiments. Human Pulmonary Artery Endothelial Cells (HPAECs) were then cultured and transferred onto the microposts which were stamped with fibronectin, a protein that would help the cells bind to the tips of the microposts. The stamping portion of the experiment required much trouble shooting and ultimately the experiments were halted here. If the research had continued the experiments would have run for 14 hours, after which the cells would be fixed in place, stained with a fluorescent dye and imaged using microscopy. These images would then be transferred to a custom written Matlab code that would calculate the deflection of the microposts and the forces induced by cells. This data could then be used to determine the effect of varying blood flow rates on the permeability of the arterial wall.