Template synthesized Microneedle Arrays for Interfacing Microalgae Cells

Genetically engineered microalgae are gaining increased interest due to their potential use in biofuel production, and in protein and drug biosynthesis. However, the cell wall that surrounds its unicellular body acts as a formidable barrier to DNA delivery. In many cases, higher transformation efficiency cannot be achieved without removing or modifying the cell wall. However, cell walls of different species have large variance in their composition, hardness and thickness, and not every cell types are compatible with such pretreatments. This talk will discuss the first example of using microneedle-array technology to deliver genes to microalgae cells with intact cell walls. The microneedle-array was prepared by a template-synthesis method. Briefly, this entails depositing a desired material into a porous template, and then removing the template to expose the replica of the template pores. This method is highly attractive because the resulting structure can easily be controlled by manipulating the pores of the template. Details on how the microneedle array is developed using the template synthesis will be described, and results on using this needle array as a tool to interface with a model microalgae specimen, Chlamydomonas Reinhardtii, will be presented

Molybdenum Disulfide-Coated Lithium Vanadium Fluorophosphate Anode: Experiments and First-Principles Calculations

To develop a new anode material to meet the increasing demands of lithium-ion battery, MoS2 is used for the first time to modify the C/LiVPO4F anode to improve its lithium-storage performance between 3 and 0.01 V. Morphological observations reveal that the MoS2-modified C/LiVPO4F particles (M-LVPF) are wrapped by an amorphous carbon as interlayer and layered MoS2 as external surface. Charge–discharge tests show that M-LVPF delivers a high reversible capacity of 308 mAh g−1 at 50 mA g−1. After 300 cycles at 1.0 A g−1, a capacity retention of 98.7 % is observed. Moreover, it exhibits high rate capability with a specific capacity of 199 mAh g−1 at 1.6 A g−1. Electrochemical impedance spectroscopy tests indicate that the lithium-ion diffusion and charge-exchange reaction at the surface of M-LVPF are greatly enhanced. First-principles calculations for the MoS2 (001)/C/LiVPO4F (010) system demonstrate that the absorption of MoS2 on C/LiVPO4F is exothermic and spontaneous and that the electron transfer at the MoS2-absorbed C/LiVPO4F surface is enhanced.postprin

A carbon nanotube-reinforced noble tin anode structure for lithium-ion batteries

A carbon nanotube (CNT)-reinforced noble tin anode structure in which CNTs fasten the tin layer to a copper underlayer has been fabricated using plating techniques so as to improve the cyclability of lithium-ion batteries. In this process, a Cu/CNTs composite layer, on one side of which CNTs protrude from the surface, is formed using a reverse current electrodeposition technique. The surface of this composite layer is subsequently coated with a tin layer by a substitution-type electroless plating technique, resulting in the CNT-reinforced noble tin anode structure. The electrochemical characteristics of this noble tin anode structure have been evaluated and compared to those of a tin anode structure without CNTs. The noble tin anode structure shows significantly improved cyclability compared with the tin anode structure and maintains a higher reversible capacity of 591 mAh g(-1), a value that is 1.6 times the theoretical capacity of graphite, even after 30 cycles.ArticleJOURNAL OF APPLIED ELECTROCHEMISTRY. 46(3):331-338 (2016)journal articl

Exploiting transport phenomena to synthesize functional materials within template nanomembranes

Thesis (Ph. D.)--University of Rochester. Department of Chemical Engineering, 2017.Template synthesis is a technique for producing materials with geometries that are defined by the geometry of their template – e.g., cylindrical wires are commonly synthesized from template membranes with cylindrical pores. This dissertation focuses on precise tuning of the template synthesized materials, enabling control over their dimensions without being limited by the shape of the template. Specifically, commercial track-etched polycarbonate filter membranes with non-parallel, cylindrical pores and in-house-prepared track-etched poly(ethylene terephthalate) (PET) membranes with parallel, conical pores are explored in this work. With the polycarbonate membrane, difference in the transport rates through the nanopore was exploited to localize template synthesis at only one surface of the membrane. This was demonstrated by using the membrane to separate a solution of small crosslinking molecules from a solution of larger oligomers. The crosslinkers diffuse faster through the membrane pores and react with the oligomer to form a hydrogel film at the surface of the nanopore membrane. A proof-of concept experiment is described using crosslinkers with imidoester moieties (dimethyl 3,3´-dithiobispropionimidate (DTBP) or dimethyl suberimidate (DMS)) and chitosan oligomers. The film’s formation is confirmed and its morphology examined with electron microscopy. Crosslinking with DTBP or DMS also confers degradability to the chitosan film. This was used to confirm successful crosslinking by monitoring the increase in transport of gold nanoparticles through the chitosan film as a function of the degradation treatment. The method presented here can potentially be used to prepare functional hydrogel thin films for biosensors, coatings, and drug delivery systems in an inexpensive, high-throughput manner. With the PET membrane, fabrication of an array of open-tipped tapered microtubes is demonstrated using a template with close-tipped conical pores, by controlling the depth of material penetration into the template pore. This was accomplished using atomic layer deposition (ALD) of Pt and pulsed-current electrodeposition (PCD) of Ni with the track-etched conical pores of a PET template membrane. The tapered microtube height is controlled by the Pt precursor pulse duration during ALD, and the microtube wall thickness is controlled by the number of cycles of Ni PCD. The microtubes’ lumen is confirmed to stay open even after 2000 cycles of Ni PCD. A potential application of the open-tipped tapered microtube array as a microinjection platform is demonstrated via successful injection of 10-nm-sized CdZnS/ZnS core/shell quantum dots into Chlamydomonas reinhardtii microalgae cells with intact cell walls. The direct delivery method demonstrated here offers novel opportunities for extending the growing interest in array-based microinjection platforms to microalgal systems. A model is also presented to simulate molecular transport during ALD in both cylindrical and conical nanopores. Using a Monte Carlo simulation method, the trajectory of particles is calculated within the pores under molecular flow, where interparticle interactions are negligible and only collisions with the pore walls are considered. Both cosine emission and diffuse elastic emission profiles from the pore wall surface are considered, and diffuse elastic emission is found to match Knudsen molecular flow theory to within 1%. To simulate ALD, a sticking probability is introduced that determines the likelihood of a reaction taking place upon collision with the pore wall. The simulation is shown to match literature-reported thickness profiles of ALD within cylindrical nanopores. In conical nanopores with a high sticking probability, it is shown that thicker deposition occurs near the pore entrance. However, with a low sticking probability the deposition is thicker near the pore end. This phenomenon is attributed to increased diffusion into the pore where the diameter is smaller and greater collision frequency takes place, providing more opportunity of reaction. This study offers theoretical understanding to ALD in closed-ended conical nanopores, and how the depth of penetration into the template pore may be controlled. Furthermore, these findings may have implications for other non-uniform geometries and may be important in estimating the minimum ALD exposure required for conformal coating therein

Optimal viscous damper design method for multi-degree-of-freedom structures by use of nonlinear programming algorithm

A design method for achieving optimal viscous damper arrangement in multi-degree-of-freedom structure is presented in this paper. The optimal damper arrangement is realized by minimizing the object function which is the sum of the additional damper coefficients under constraints to be provided by allowable response displacement of each story. Giving the maximum response displacement of each story as the function of the additional viscous damper coefficients evaluated by use of the SRSS method enables to apply the nonlinear programming algorithm for solving the minimizing problem. The optimal damper arrangements for two sample structure models under the action of horizontal ground acceleration are implemented by the proposed design method and their reasonability is thoroughly discussed

Heat Treatment for the Stabilization of Hydrogen and Vacancies in Electrodeposited Ni-Fe Alloy Films

In an effort to realize the long-term stability of the magnetostrictive property of electrodeposited Ni-Fe alloy films, heat treatments needed for eliminating the possible effect of hydrogen and hydrogen-induced vacancies have been investigated, mainly by use of thermal desorption spectroscopy. While metal-atom vacancies begin to move only above $500 K, hydrogen atoms can undergo slow motion and concomitant changes of state at room temperature, and are therefore believed to be a major cause of the long-term drift of the magnetism. Hydrogen atoms dissolved on regular interstitial sites can be completely removed by high-frequency pulse heating to 668 K, and those trapped by vacancies with relatively low binding energies by additional heat treatments to 453 K for over 1 h. This combination of heat treatments was found to reduce substantially the change of state of hydrogen during subsequent aging tests (383 K for 400 h), and proved to be effective for ensuring the longterm stability of magnetostrictive Ni-Fe film sensors

Explanation of jumping behavior of Chozu-sha in view of dynamics of discontinuous system

At Kumamoto earthquake on April 16, 2016, at 1:25 AM, the jumping behavior of the unanchored wooden structure named Chozu-sha was reported. To explain it in view of dynamics of discontinuous systems, the Chozu-sha is modeled by two-story rigid rectangular block, and its equations of motion are derived. Employing a corresponding recorded accelerogram, its jumping motion is computed. Comparison of the jumping distance computed with that reported yields that the proposed procedure may explain a major mechanism of the jumping of the Chozu-sha. Its essence is that the jumping distance is elongated if the horizontal acceleration which is larger than the rocking commencement acceleration but is smaller than the maximum acceleration lasts longer