Browsing by Department "Applied Mechanics"

An analytical solution is provided for a two-equation coupled model for determination of liver tissue temperature during radio frequency ablation in the steady state with one-dimension in space. Both analytical analysis and model simulation were conducted to investigate the effects of two crucial system parameters: blood perfusion rate and convective heat transfer coefficient on the tissue temperature field. The quantitative criteria were also derived, under which the two-equation coupled system can be approximated to a conventional single bio-heat equation system such as the Pennes model. ?2009 IEEE.

This work demonstrates, for the first time, internal resonance with a ratio as high as 1:6 in micromechanical CC-beam resonators. Particularly, multiple-stepped beams, ilar to that used in [1] but with additional segments, of which the specifically tailored dimensions achieve the multiplication between its 1st and 3rdin-plane modes. Based on a CMOS-MEMS process platform, the stepped structure boosts the effect of geometric nonlinearity, resulting in strong intermodal coupling which leads to the 1:6 internal resonance. Instead of applying FEA to directly obtain the dimensions, this work first transforms the Euler-Bernoulli beam equation into algebraic expressions based on the Adomian decomposition method (ADM) [2], and then locates the initial combination using contour plots for the following fine tune in FEA. In addition to internal resonance, frequency combs are observed, possibly resulting from unidirectional mechanical excitation [3]. © 2022 IEEE.

Fused deposition modeling (FDM) is the most commonly used 3D printing technique that directly extrudes molten materials layer by layer and overcomes the constraints of fabricating complicate geometries. This technique is fast, relatively easy to perform, thus more economical compared to other 3D printing methods. However, the materials that can be extruded by FDM are limited to polymers at the present time. This study aimed to develop a fused deposition modeling for metals (FDMm) system that can deposit metallic structures directly on a platform. An extruding nozzle designed by the researchers was connected to a commercial fused deposition machine to extend the materials selection from polymers to low melting temperature metals. Continuous Sn99.3Cu0.7 lead free solder and Sn60Pb40 lead free solder were successfully extruded in a linear shape and showed that the fabrication parameters for metals are significantly different from those for polymers. Controlling the fabrication parameters also allowed the deposition of metal at a uniform geometry. Optical microscopy and scanning electron microscopy were used to analyze the FDMm-fabricated samples. Good layer to layer bonding and overall material strength can be achieved by fine-tuning of process parameters. © 2016 IEEE.

Hydrogels show promise in preventing inorganic catalysis aggregation during hydrogen evolution. However, the incompatible intrinsic properties of inorganics and hydrogels can cause catalyst release during the reaction. One solution is incorporating polymer photocatalysts into hydrogels, but low photocatalytic efficiency due to anti-synergetic effects between polymers and hydrogels remains a challenge. Herein, we developed all-in-one photocatalytic microreactors (PMRs) with excellent stability and efficiency by strongly entangling polymers with hydrogels and designing heterogeneous hydrogels. This approach prevents catalyst loss while achieving a high hydrogen evolution efficiency, self-healability, and stretchability. Moreover, PMRs maintain their efficiency even after they undergo freeze-drying and rehydration. Remarkably, we demonstrate the construction of PMRs into three-dimensional (3D) structures via 3D-printing at room temperature without additional supporting material. In light of these advantages, we have demonstrated a strategy for rapidly manufacturing PMRs with high stability, reactivity, and 3D-printability, which has significant potential for practical applications. © 2024 American Chemical Society

Bacteria are similar to social organisms that engage in critical interactions with one another, forming spatially structured communities. Despite extensive research on the composition, structure, and communication of bacteria, the mechanisms behind their interactions and biofilm formation are not yet fully understood. To address this issue, scanning probe techniques such as atomic force microscopy (AFM), scanning electrochemical microscopy (SECM), scanning electrochemical cell microscopy (SECCM), and scanning ion-conductance microscopy (SICM) have been utilized to analyze bacteria. This review article focuses on summarizing the use of electrochemical scanning probes for investigating bacteria, including analysis of electroactive metabolites, enzymes, oxygen consumption, ion concentrations, pH values, biofilms, and quorum sensing molecules to provide a better understanding of bacterial interactions and communication. SECM has been combined with other techniques, such as AFM, inverted optical microscopy, SICM, and fluorescence microscopy. This allows a comprehensive study of the surfaces of bacteria while also providing more information on their metabolic activity. In general, the use of scanning probes for the detection of bacteria has shown great promise and has the potential to provide a powerful tool for the study of bacterial physiology and the detection of bacterial infections. © 2023 by the authors.

In this work, we demonstrate a promising polysilicon nanowire (poly-Si NW) biosensor platform. Several biomarkers, such as N-terminal prohormone brain natriuretic peptide (NT-proBNP), Low-density lipoprotein (LDL), Hemoglobin (Hb), and Hemoglobin A1C (HbA1c), for heart disease and diabetes are experimentally examined by the developed platform. Based on experimental results, the sensor responses of each biomarker is suitable for clinical diagnoses. Compared with conventional examination methods, using polysilicon nanowire biosensor not only reduce the inspection time but also economize the cost of diagnoses. Moreover, these implemented biosensor platform are made by a standard complementary metal-oxide-semiconductor (CMOS) process. Based on this technology, the developed devices can be easily integrated with different functional modules, such wireless and microfluidic systems. Therefore, this work demonstrates a good potential of CMOS based biosensor platform to accomplish the need of early diagnosis and point-of-care testing (POCT) system. ? 2014 The Authors. Published by Elsevier Ltd.