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Department of Mechanical EngineeringIn recent years, extensive efforts have been devoted to developing antibiofilm material which can effectively prevent biofilm formation. Currently, the most common method of preventing protein or bacteria adhesion is to impart surface functionalization using PEGylated materials or zwitterionic materials with excellent antifouling properties. This method is resistant to the surface adhesion of proteins and microorganisms but is less mechanically durable and easily damaged by external physical and chemical stimuli, which can lead to the loss of antifouling performance. Bactericidal methods include chemical killing by antibiotics and physical killing due to surface structure. Chemical methods using silver, nitrates, or copper can cause microbial infections due to antibiotic resistance and can be toxic and biologically harmful. To avoid this problem, researchers have been studying physical killing methods. Nanostructures which can be fabricated using silicon, metal, or polymers have been used to kill bacteria. However, these methods also have many limitations, such as complex fabrication methods, high cost, secondary biofilm formation, and especially the problem of the remaining dead bacterial carcasses. Furthermore, many previous studies, whether concerning the chemical or mechanical approaches, have focused on a single strategy, such as antifouling coatings, bactericidal materials, or nanopatterning. However, these single-strategy approaches have many limitations, such as the drug resistance of bacteria, toxicity to cells and the environment, low antifouling performance, high cost, or low mechanical and chemical durability in the prevention of biofilm formation. Therefore, to overcome these many drawbacks first of all, simple, cost-effective, environmentally friendly and reproducible fabrication methods are strongly required. Moreover, to overcome several problems of the single-strategy approaches, a multi-strategy or hybrid approach should be considered. This dissertation presents the development of a hybrid strategy based on an antifouling material and bactericidal nanostructures that aim to combine both the antifouling and bactericidal functions to maintain effective anti-biofouling performance. Our hybrid anti-biofouling surface consists of nanostructures with the biocompatible materials polyethylene glycol dimethacrylate (PEGDMA) and cellulose acetate (CA). The biocompatible nanostructure array was easily fabricated using UV molding and soft lithography. Moreover, 2-methacryloyloxyethyl phosphorylcholine (MPC), a zwitterionic polymer, was covalently grafted onto the fabricated nanostructures for superior antifouling performance. The surface can be applied to various 3D surfaces and large areas, due to the flexibility of the base material. Based on the synergetic integration of the bio- and ecofriendly nanostructural polymer and MPC, our hybrid strategy can easily fabricate an efficient anti-biofouling surface which can overcome the limitations of previous antifouling and antibacterial surfaces. Furthermore, our hybrid surface has high chemical / structural stability even in wet conditions. Not only can it effectively prevent bacterial attachment, but it also exhibits better bactericidal effects, regardless of the bacterial types, compared with single anti-biofouling strategies (repelling bacteria or killing bacteria). Furthermore, it preserves robust and excellent anti-biofouling activity, even under external stimuli and long-term fouling tests. This novel hybrid anti-biofouling surface provides a more-promising solution for the prevention of initial bacterial attachment and subsequent biofilm formation. In particular, the hybrid anti-biofouling function makes these surfaces more suitable for applications in which long-term antibacterial activity is required. Also, our developed surfaces can play an important role in solving bio-contamination problems in the medical and marine industries.clos

Strong and Reversible Adhesion of Interlocked 3D-Microarchitectures

Diverse physical interlocking devices have recently been developed based on one-dimensional (1D), high-aspect-ratio inorganic and organic nanomaterials. Although these 1D nanomaterial-based interlocking devices can provide reliable and repeatable shear adhesion, their adhesion in the normal direction is typically very weak. In addition, the high-aspect-ratio, slender structures are mechanically less durable. In this study, we demonstrate a highly flexible and robust interlocking system that exhibits strong and reversible adhesion based on physical interlocking between three-dimensional (3D) microscale architectures. The 3D microstructures have protruding tips on their cylindrical stems, which enable tight mechanical binding between the microstructures. Based on the unique 3D architectures, the interlocking adhesives exhibit remarkable adhesion strengths in both the normal and shear directions. In addition, their adhesion is highly reversible due to the robust mechanical and structural stability of the microstructures. An analytical model is proposed to explain the measured adhesion behavior, which is in good agreement with the experimental results

A lab-on-a-disc platform enables serial monitoring of individual CTCs associated with tumor progression during EGFR-targeted therapy for patients with NSCLC

Rationale: Unlike traditional biopsy, liquid biopsy, which is a largely non-invasive diagnostic and monitoring tool, can be performed more frequently to better track tumors and mutations over time and to validate the efficiency of a cancer treatment. Circulating tumor cells (CTCs) are considered promising liquid biopsy biomarkers; however, their use in clinical settings is limited by high costs and a low throughput of standard platforms for CTC enumeration and analysis. In this study, we used a label-free, high-throughput method for CTC isolation directly from whole blood of patients using a standalone, clinical setting-friendly platform. Methods: A CTC-based liquid biopsy approach was used to examine the efficacy of therapy and emergent drug resistance via longitudinal monitoring of CTC counts, DNA mutations, and single-cell-level gene expression in a prospective cohort of 40 patients with epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer. Results: The change ratio of the CTC counts was associated with tumor response, detected by CT scan, while the baseline CTC counts did not show association with progression-free survival or overall survival. We achieved a 100% concordance rate for the detection of EGFR mutation, including emergence of T790M, between tumor tissue and CTCs. More importantly, our data revealed the importance of the analysis of the epithelial/mesenchymal signature of individual pretreatment CTCs to predict drug responsiveness in patients. Conclusion: The fluid-assisted separation technology disc platform enables serial monitoring of CTC counts, DNA mutations, as well as unbiased molecular characterization of individual CTCs associated with tumor progression during targeted therapy

Numerical simulation on the two-phase flow pattern in the loop heat pipe with r-134a

This paper discusses the two-phase flow pattern in the loop heat pipe with R-134a. A computational fluid dynamics (CFD) study was carried out using ANSYS FLUENT. VOF model was used to simulate interface between vapor and liquid phase of R- 134a. A UDF was used to model evaporation and condensation mass transfer between two phases. For the simulation of increase of pressure in the loop heat pipe, the ideal gas law was considered when modelling the density of vapor. The numerically calculated temperatures in this paper and Fadhl’s calculated temperatures and experimentally measured temperatures matched very well [2]. The maximum difference between the calculated and Fadhl’s temperature data is 2.4 %. The bubble figure in the loop heat was observed with time passed in this paper.Papers presented at the 13th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Portoroz, Slovenia on 17-19 July 2017 .International centre for heat and mass transfer.American society of thermal and fluids engineers

A Distributed ADMM Approach to Non-Myopic Path Planning for Multi-Target Tracking

This paper investigates non-myopic path planning of mobile sensors for multi-target tracking. Such problem has posed a high computational complexity issue and/or the necessity of high-level decision making. Existing works tackle these issues by heuristically assigning targets to each sensing agent and solving the split problem for each agent. However, such heuristic methods reduce the target estimation performance in the absence of considering the changes of target state estimation along time. In this work, we detour the task-assignment problem by reformulating the general non-myopic planning problem to a distributed optimization problem with respect to targets. By combining alternating direction method of multipliers (ADMM) and local trajectory optimization method, we solve the problem and induce consensus (i.e., high-level decisions) automatically among the targets. In addition, we propose a modified receding-horizon control (RHC) scheme and edge-cutting method for efficient real-time operation. The proposed algorithm is validated through simulations in various scenarios.Comment: Copyright 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other work

Flexible and Shape-Reconfigurable Hydrogel Interlocking Adhesives for High Adhesion in Wet Environments Based on Anisotropic Swelling of Hydrogel Microstructures

This study presents wet-responsive, shape-reconfigurable, and flexible hydrogel adhesives that exhibit strong adhesion under wet environments based on reversible interlocking between reconfigurable microhook arrays. The experimental investigation on the swelling behavior and structural characterization of the hydrogel microstructures reveal that the microhook arrays undergo anisotropic swelling and shape transformation upon contact with water. The adhesion between the interlocked microhook arrays is greatly enhanced under wet conditions because of the hydration-triggered shape reconfiguration of the hydrogel microstructures. Furthermore, wet adhesion monotonically increases with water-exposure time. A maximum adhesion force of 79.9 N cm-2 in the shear direction is obtained with the hydrogel microhook array after 20 h of swelling, which is 732.3% greater than that under dry conditions (i.e., 9.6 N cm-2). A simple theoretical model is developed to describe the measured adhesion forces. The results are in good agreement with the experimental data

LOWER EXTREMITY KINEMATICS OF SKI MOTION ON HILLS

This research study aimed to collect thre- dimensional joint angles of the lower extremity during a basic ski motion in order to provide more quantitative teaching guide-lines for ski instructors. Eleven infrared cameras were placed to cover the capture volume of three different stopping movements (e.g. “Pflug Fahren”) on hills. Six ski instructors participated in the test. Three trials of each stop were selected for comparison. Based on the results, skiers tended to use the edge of the ski and maintain a wider “V” shape at the shortest stop distance (e.g. 2m) compared to the other stops. Also, each skier had to invert the foot with a less flexed and more abducted knee and hip position as the stopping distance was decreased. This information will be useful for the development of more objective teaching guide-lines for beginner skiers