Chiun Peng Lee

The effect of boron on the corrosion resistance of the high entropy alloys Al0.5CoCrCuFeNiBx

High entropy alloys are a newly developed family of multicomponent alloys that consist of various major alloying elements, including copper, nickel, aluminum, cobalt, chromium, iron, and others. Each element in the alloy system is present at between 5 and 35 atom %. A high entropy alloy has numerous beneficial mechanical, magnetic, and electrochemical characteristics. This investigation discusses the corrosion resistance of the Al 0.5 CoCrCuFeNiB x alloys with various amounts of added boron. Surface morphological and chemical analyses verified that the addition of boron produced Cr, Fe, and Co borides. Therefore, the fraction of Cr outside borides precipitates was scant. The anodic polarization curves and electrochemical impedance spectra of the Al 0.5 CoCrCUFeNiB x alloys, obtained in 1 N H 2 SO 4 aqueous solution, clearly reveal that the general corrosion resistance decreases as the concentration of boron increases.

Hysteresis in a Microactuator With Single-Domain Magnetic Thin Films

An actuator with single-domain magnetic thin films is designed to investigate the actuation in the application of a magnetic field. The single-domain magnetic thin film used in this study has high shape anisotropy, and the single-domain magnetization is observed using magnetic force microscope. The hysteresis in the planar deflection of the cantilever beam is found, and the magnetic switching behavior of the single-domain magnetic thin films is also observed in the actuation.

Ordered magnetic microdroplets array on magnetic films

With the development of magnetic droplet-based biochips, the manipulation of magnetic droplets has become an important issue. In this study, deposited magnetic circular films are used to assist the positioning of magnetic microdroplets, which are separated from a mother droplet caused by the Rosensweig instability under a magnetic field. Magnetic microdroplets are attracted by the concentrated magnetic flux density caused by out-of-plane magnetization of the magnetic films, and magnetic films confine the positions of droplets. Through adjusting the applied field strength, droplet arrays with different number densities can be obtained. One-to-one correspondences between droplets and magnetic films can be achieved within specific magnetic field ranges.

Influence of Different Onion States on Magnetization Reversal Processes in Permalloy Rings

Simulation and experiment are performed to investigate the influence of onion states with different-helicity pair vortices on the magnetization reversal process. It is found that for the onion state that has pair vortices with the same helicity, flux-closure state occurs in the reversal process; for the onion state that has pair vortices with opposite helicity, flux-closure state does not occur in the reversal process, and the onion state transforms directly to the reverse onion state. In addition, notches at the same side and diagonal notches with respect to the field direction are designed on the permalloy rings to induce onion states with same-helicity pair vortices and opposite-helicity pair vortices, respectively, for the control of the three-step and two-step magnetization reversal processes.

Fabrication of hexagonally packed cell culture substrates using droplet formation in a T-shaped microfluidic junction

A method is here proposed to fabricate ordered hexagonally packed cell culture substrates with hexagonally arranged cell patterning areas. We generated photo-sensitive polymeric microdroplets in a T-shaped microfluidic junction by an immiscible liquid, and then solidified the collective self-assembled hexagonal droplet array to obtain the cell culture substrate, on which we took the grooves formed between the solidified droplets as the hexagonally arranged cell patterning areas. The most promising advantage of our method is that we can actively tune the droplet size by simply adopting different volumetric flow rates of the two immiscible fluids to form cell culture substrates with differently sized cell patterning areas. Besides, the examination results of the cell culture substrates characteristics validate whether our method is capable of creating substrates with high spatial uniformity. To verify the cell patterning function of our cell culture substrates, we used the semi-adherent RAW cells to demonstrate the effectiveness of patterning of suspended/adherent cells before/after adhesion. Over 90% cell viability and cell patterning rate suggest that our method may be a promising approach for future applications of cell patterning on biochips.A method is here proposed to fabricate ordered hexagonally packed cell culture substrates with hexagonally arranged cell patterning areas. We generated photo-sensitive polymeric microdroplets in a T-shaped microfluidic junction by an immiscible liquid, and then solidified the collective self-assembled hexagonal droplet array to obtain the cell culture substrate, on which we took the grooves formed between the solidified droplets as the hexagonally arranged cell patterning areas. The most promising advantage of our method is that we can actively tune the droplet size by simply adopting different volumetric flow rates of the two immiscible fluids to form cell culture substrates with differently sized cell patterning areas. Besides, the examination results of the cell culture substrates characteristics validate whether our method is capable of creating substrates with high spatial uniformity. To verify the cell patterning function of our cell culture substrates, we used the semi-adherent RAW cells to demonstrate the effectiveness of patterning of suspended/adherent cells before/after adhesion. Over 90% cell viability and cell patterning rate suggest that our method may be a promising approach for future applications of cell patterning on biochips.

Magnetic Cell Patterning on Hexagonally Packed Cell Culture Substrates

In this study, we used a T-junction microfluidic to fabricate hexagonally packed cell culture substrates involving ferrofluid for magnetic cell patterning. Polymeric microdroplets, which constituted the main structure of the cell culture substrates, were made by generation of a photo-sensitive polymer material in the T-shaped microfluidic junction by an immiscible liquid. The self-assembled droplet array then was solidified to form the hexagonally-packed cell culture substrates, followed by the filling of ferrofluid in the gaps between the solidified droplets for magnetic cell patterning. The advantages of our technique include different unit cell patterning areas of cell culture substrates can be created by only adjusting the volumeric flow rates without having to change the microfluidic channel, and the magnetic modification of the cell culture substrate is very easy. Furthermore, high spatial uniformity of the cell culture substrates is also promised. Magnetic cell patterning experiment was performed to verify the feasibility of our cell culture substrates.

Field Evolution of Magnetization States With Different Combinations of Vortex Cores and Anti-Vortex Cores in Different Helicities

Field evolution of two types of mixed states made of four vortex cores and two anti-vortex cores are investigated numerically. The two types of mixed states both consist of one rhombic domain and one or two cross-tie walls. The two mixed states are found to exhibit different magnetization processes. As the field is applied along the long side direction, both mixed states exhibit two steps in magnetization curves; as the field is applied in parallel or antiparallel to the magnetization direction of the rhombic domain, however, it may exhibit two-step or three-step characteristic depending on its magnetization configuration.

Fabrication of Microlens Arrays by Utilizing Magnetic Hydrodynamic Instability of Ferrofluid Droplets

This study proposes an actively controllable method for fabrication of polymer microlens arrays. Hexagonal arrays of ferrofluid droplets, which were utilized as the mother-mold masters for microlens molding, were generated by inducing the magnetic hydrodynamic instability under different magnetic fields. To fabricate numerous cavity molds for microlens array molding, we used the field-dependent shapes of the ferrofluid droplets to create different sized molds. For the fabricated microlens arrays, their field-dependent bottom areas, lens height, radii of curvature, and the fill-factor were discussed. Furthermore, performances of the microlenses, including the numerical aperture, focal length, and depth of field, were tested.