3D Insulator‐based dielectrophoresis using DC‐biased,AC electric fields for selective bacterial trapping

Insulator‐based dielectrophoresis (iDEP) is a well‐known technique that harnesses electric fields for separating, moving, and trapping biological particle samples. Recent work has shown that utilizing DC‐biased AC electric fields can enhance the performance of iDEP devices. In this study, an iDEP device with 3D varying insulating structures analyzed in combination with DC biased AC fields is presented for the first time. Using our unique reactive ion etch lag, the mold for the 3D microfluidic chip is created with a photolithographic mask. The 3D iDEP devices, whose largest dimensions are 1 cm long, 0.18 cm wide, and 90 μm deep are then rapidly fabricated by curing a PDMS polymer in the glass mold. The 3D nature of the insulating microstructures allows for high trapping efficiency at potentials as low as 200 Vpp. In this work, separation of Escherichia coli from 1 μm beads and selective trapping of live Staphylococcus aureus cells from dead S. aureus cells is demonstrated. This is the first reported use of DC‐biased AC fields to selectively trap bacteria in 3D iDEP microfluidic device and to efficiently separate particles where selectivity of DC iDEP is limited.     

TEM study of annealed Pt nanostructures grown by electron beam-induced deposition

In this paper we report on the microstructural characterization of Pt nanostructures fabricated by electron beam-induced deposition in a dual beam system and subsequently annealed in furnace. The as-deposited nanostructures are made of a mixture of nanocrystalline Pt and amorphous carbon. We show by transmission electron microscopy and electron energy loss spectroscopy that the annealing in presence of oxygen at 550 °C for 30 min is able to remove the amorphous carbon from the nanostructure, leaving polycrystalline Pt grains.     

Growth Modeling of Fiber Gratings: A Numerical Investigation

We have developed a simple method to analyze the growth process of fiber gratings (FGs) in the core of photorefractive optical fibers. It is based on the exponential saturation model and it takes into account the type of photosensitive fiber used, the exposure times, and the incident optical power. The photorefractive fiber has been characterized by two parameters: the saturation photoinduced refractive index change and the saturation energy, which can be obtained experimentally. We carry out a numerical investigation for the growth process of a uniform FG. The experimentally observed phenomena of shifting the Bragg optical frequency with exposure times and the appearance of higher-order Bragg resonances are predicted and discussed.     

Fabrication of chloroform sensor based on hydrothermally prepared low-dimensional β-Fe2O3 nanoparticles

Hydrothermally prepared as-grown low-dimensional nano-particles (NPs) have been characterized using UV–vis spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, powder X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Raman spectroscopy, and electron dispersion spectroscopy (EDS). The uniformity of the nano-material was executed by the scanning electron microscopy, where the single phase of the nano-crystalline β-Fe₂O₃ was characterized using XRD techniques. β-Fe₂O₃ nanoparticles fabricated glassy carbon electrode (GCE) have improved chloroform-sensing performances in terms of electrical response (I–V technique) for detecting analyte in liquid phase. The analytical performances were investigated, which showed that the better sensitivity, stability, and reproducibility of the sensor improved significantly by using Fe₂O₃ NPs thin-film on GCE. The calibration plot was linear (R = 0.9785) over the large range of 12.0 μM to 12.0 mM. The sensitivity was calculated as 2.1792 μA cm⁻² mM⁻¹ with a detection limit of 4.4 ± 0.10 μM in short response time (10.0 s).     

Analytical Study of Filters Dimensions and Spectral Thermal Effects on Optical Filters Operation Performance Characteristics

We study the different optical filters design considerations over wide range of the operation conditions in near infrared optical spectrum transmission region. There are many operating conditions parameters describing optical filter properties such as the amount absorbed electromagnetic radiation which depends on the operating signal wavelength; the amount of the absorbing material in the filter thickness; and the absorption coefficient of the material at that wavelength. Filter modulation depth, filtration signal quality, filter delay time, filter bit error rate, and filter correction are the major interesting performance parameters in the current study. Best candidate materials based optical filters are used which namely barium fluoride (BaF₂), and zinc selenide (ZnSe) and compared with published measured works. Our results are validated against published experimental studies and show a good agreement and matching.     

Al/AlO_x/Al超导隧道结的制备工艺研究

研究了在高阻硅衬底上Al/AlO x/Al隧道结的制备技术,采用电子束蒸发制备Al/AlO x/Al三层材料,湿法刻蚀制备底电极和上电极以及电路连线,PECVD法生长绝缘层(SiO2)保护超导隧道结,RIE刻蚀上电极窗口。在400mK温度下测量了Al/AlO x/Al隧道结样品,得到了较好的隧道结I-V曲线,能隙电压Vg为0.325mV,超导临界电流I c为55nA,漏电流为5nA。     

Surface modification of polymer microfluidic devices using in-channel atom transfer radical polymerization

In-channel atom transfer radical polymerization (ATRP) was used to graft a PEG layer on the surface of microchannels formed in poly(glycidyl methacrylate)-co-(methyl methacrylate) (PGMAMMA) microfluidic devices. The patterned and cover plates were first anchored with ATRP initiator and then thermally bonded together, followed by pumping a solution containing monomer, catalyst, and ligand into the channel to perform ATRP. A PEG-functionalized layer was grafted on the microchannel wall, which resists protein adsorption. X-ray photoelectron spectroscopy (XPS) was used to investigate the initiator-bound surface, and EOF was measured to evaluate the PEG-grafted PGMAMMA microchannel. Fast, efficient, and reproducible separations of amino acids, peptides, and proteins were obtained using the resultant microdevices. Separation efficiencies were higher than 1.0x10(4) plates for a 3.5 cm separation microchannel. Compared with microdevices modified using a previously reported ATRP technique, these in-channel modified microdevices demonstrated better long-term stability.     

A Simple and Inexpensive Method for Fabrication of Ultramicroelectrode Array and Its Application for the Detection of Dissolved Oxygen

Herein, we report a simple and inexpensive way for fabrication of ultramicroelectrode arrays (UMEAs) and the relative characterization methods. The fabrication of UMEAs involves only a few steps of handwork. Since only metal wires and epoxy are used through the fabrication process, it is supposed to be a quite straightforward method for preparing UMEAs. A dissolved oxygen (DO) sensor based on UMEAs was constructed. The detection of DO in different aqueous samples is fast, reliable and reproducible. The surface of UMEAs fabricated can be renewed simply by mechanically polishing or electrochemical treatment, which is of great advantage to practical applications.     

Multiscale Dot-Wire-Sheet Heterostructured Nitrogen-Doped Carbon Dots-Ti3C2Tx/Silk Nanofibers for High-Performance Fiber-Shaped Supercapacitors

Fiber-shaped supercapacitors (FSCs) have become one of the significantly strategical flexible energy-storage materials towards future wearable textile electronics and metaverse technologies. Here, we develop the high-performance FSCs based on multiscale dot-wire-sheet heterostructure microfiber of nitrogen-doped carbon dots-Ti₃C₂T_x/silk nanofibers (NCDs-Ti₃C₂T_x/SNFs) hybrids via microfluidic fabrication. Due to the enlarged interlayer spacing, plentiful porous channels, accelerated H⁺ ion transport dynamics, large electrical conductivity and excellent mechanical strength/flexibility, the NCDs-Ti₃C₂T_x/SNFs possesses high volumetric capacitance (2218.7 F cm⁻³) and reversible charge–discharge stability in 1 M H₂SO₄ electrolyte. Furthermore, the solid-state FSCs present high energy density (57.9 mWh cm⁻³), good capacitance (1157 F cm⁻³), long-life cycles (82.3 % capacitance retention after 40000 cycles), which realize the actual energy-supply applications (powering lamp, watch and toy car).     

Photo-RAFT Polymerization for Hydrogel Synthesis through Barriers and Development of Light-Regulated Healable Hydrogels under NIR Irradiation

We report an aqueous and near-infrared (NIR) light mediated photoinduced reversible addition–fragmentation chain transfer (photo-RAFT) polymerization system catalyzed by tetrasulfonated zinc phthalocyanine (ZnPcS₄⁻) in the presence of peroxides. Taking advantage of its fast polymerization rates and high oxygen tolerance, this system is successfully applied for the preparation of hydrogels. Exploiting the enhanced penetration of NIR light, photoinduced gelation is effectively performed through non-transparent biological barriers. Notably, the RAFT agents embedded in these hydrogel networks can be reactivated on-demand, enabling the hydrogel healing under NIR light irradiation. In contrast to the minimal healing capability (<15 %) of hydrogels prepared by free radical polymerization (FRP), RAFT-mediated networks display more than 80 % recovery of tensile strength. Although healable polymer networks under UV and blue lights have already been established, this work is the first photochemistry system using NIR light, facilitating photoinduced healing of hydrogels through thick non-transparent barriers.