Antimicrobial and Antifouling Effects of Petal-Like Nanostructure by Evaporation-Induced Self-Assembly for Personal Protective Equipment.

Although the personal protective equipment (PPE) used by healthcare workers (HCWs) effectively blocks hazardous substances and pathogens, it does not fully rule out the possibility of infection, as pathogens surviving on the fabric surface pose a substantial risk of cross-infection through unintended means. Therefore, PPE materials that exhibit effective biocidal activity while minimizing contamination by viscous body fluids (e.g., blood and saliva) and pathogen-laden droplets are highly sought. In this study, petal-like nanostructures (PNSs) are synthesized through the vertical rearrangement of colloidal lamellar bilayers via evaporation-induced self-assembly of octadecylamine, silica-alumina sol, and diverse photosensitizer. The developed method is compatible with various fabrics and imparts visible-light-activated antimicrobial and superhydrophobic-based antifouling activities. PNS-coated fabrics could provide a high level of protection and effectively block pathogen transmission as exemplified by their ability to roll off viscous body fluids reducing bacterial droplet adhesion and to inactivate various microorganisms. The combination of antifouling and photobiocidal activities results in the complete inactivation of sprayed pathogen-laden droplets within 30 min. Thus, this study paves the way for effective contagious disease management and the protection of HCWs in general medical environments, inspiring further research on the fabrication of materials that integrate multiple useful functionalities.

Degradation Feature Extraction Method for Prognostics of an Extruder Screw Using Multi-Source Monitoring Data.

Laboratory-scale data on a component level are frequently used for prognostics because acquiring them is time and cost efficient. However, they do not reflect actual field conditions. As prognostics is for an in-service system, the developed prognostic methods must be validated using real operational data obtained from an actual system. Because obtaining real operational data is much more expensive than obtaining test-level data, studies employing field data are scarce. In this study, a prognostic method for screws was presented by employing multi-source real operational data obtained from a micro-extrusion system. The analysis of real operational data is more challenging than that of test-level data because the mutual effect of each component in the system is chaotically reflected in the former. This paper presents a degradation feature extraction method for interpreting complex signals for a real extrusion system based on the physical and mechanical properties of the system as well as operational data. The data were analyzed based on general physical properties and the inferred interpretation was verified using the data. The extracted feature exhibits valid degradation behavior and is used to predict the remaining useful life of the screw in a real extrusion system.

Integrated, Automated, Fast PCR System for Point-Of-Care Molecular Diagnosis of Bacterial Infection.

We developed an integrated PCR system that performs automated sample preparation and fast polymerase chain reaction (PCR) for application in point-of care (POC) testing. This system is assembled from inexpensive 3D-printing parts, off-the-shelf electronics and motors. Molecular detection requires a series of procedures including sample preparation, amplification, and fluorescence intensity analysis. The system can perform automated DNA sample preparation (extraction, separation and purification) in ≤5 min. The variance of the automated sample preparation was clearly lower than that achieved using manual DNA extraction. Fast thermal ramp cycles were generated by a customized thermocycler designed to automatically transport samples between heating and cooling blocks. Despite the large sample volume (50 µL), rapid two-step PCR amplification completed 40 cycles in ≤13.8 min. Variations in fluorescence intensity were measured by analyzing fluorescence images. As proof of concept of this system, we demonstrated the rapid DNA detection of pathogenic bacteria. We also compared the sensitivity of this system with that of a commercial device during the automated extraction and fast PCR of Salmonella bacteria.

Highly reproducible quantification of apoptotic cells using micropatterned culture of neurons.

The quantification of apoptotic cells is an integral component of many cell-based assays in biological studies. However, current methods for quantifying apoptotic cells using conventional random cultures have shown great limitations, especially for the quantification of primary neurons. Randomly distributed neurons under primary culture conditions can lead to biased estimates, and vastly different estimates of cell numbers can be produced within the same experiment. In this study, we developed a simple, accurate, and reliable technique for quantifying apoptotic neurons by means of micropatterned cell cultures. A polydimethylsiloxane (PDMS) microstencil was used as a physical mask for micropatterning cell cultures, and primary granular neurons (GNs) were successfully cultured within the micropattern-confined regions and homogeneously distributed over the entire field of each pattern. As compared with the conventional method based on random cultures, the micropatterned culture method allowed for highly reproducible quantification of apoptotic cells. These results were also confirmed by using GNs derived from mice with neurodegeneration. We hope that this micropatterning method based on the use of a PDMS microstencil can overcome the technical obstacles existing in current biological studies and will serve as a powerful tool for facilitating the study of apoptosis-involved diseases.

Preparation of Microstructure Molds of Montmorillonite/Polyethylene Glycol Diacrylate and Multi-Walled Carbon Nanotube/Polyethylene Glycol Diacrylate Nanocomposites for Miniaturized Device Applications.

Environmentally friendly microstructure molds with montmorillonite (MMT) or multi-walled carbon nanotube (MWCNT) reinforced polyethylene glycol diacrylate (PEGDA) nanocomposites have been prepared for miniaturized device applications. The micropatterning of MMT/PEGDA and MWCNT/PEGDA with 0.5 to 2.0 wt% of MMTs and MWCNTs was achieved through a UV curing process with micro-patterned masks. Hexagonal dot arrays and complex patterns for microstructures of the nanocomposites were produced and characterized with an optical microscope; their thermal properties were studied by thermogravimetric analysis (TGA). The TGA results showed that these nanocomposites were thermally stable up to 350 °C. Polydimethylsiloxane thin replicas with different microstructures were prepared by a casting method using the microstructured nanocomposites as molds. It is considered that these microstructure molds of the nanocomposites can be used as microchip molds to fabricate nanobio-chips and medical diagnostic chip devices.

Preparation of 3D electrode microarrays of multi-walled carbon nanotubes/nafion nanocomposites for microfluidic biofuel cells.

Three-dimensional (3D) electrode microarrays with multi-walled carbon nanotubes (MWCNTs) reinforced Nafion nanocomposites were prepared for microfluidic biofuel cells. The oxidized MWCNTs (ox-MWCNTs) were prepared using chemical reactions with 60% nitric acid solution with pristine MWCNTs at 120 degrees C for 12 hrs with a nitrogen gas flow environment. Ox-MWCNTs in the range of 1 to 20 wt.% based on the Nafion polymer weight were reinforced to Nafion nanocomposites by solution casting. The micro-porous structure of the ox-MWCNTs reinforced Nafion nanocomposites was prepared by plasma etching for 5 to 20 min. The 10 wt.% ox-MWCNTs reinforced Nafion nanocomposite produced stable micro-porous structures of 3D electrodes by 10 min plasma etching. Micro-scale 3D structures of MWCNTs reinforced Nafion nanocomposites in a diameter range of 47 to 300 µm were prepared by the micro-stencil assisted casting. To characterize the 3D electrode microarrays, the physical geometry and the reinforced MWCNT dispersion in the nanocomposite structure were examined using a scanning electron microscope (SEM) and an optical microscope. Thermal property measurements of the ox-MWCNTs reinforced Nafion nanocomposites with 10 min of plasma etching, and without plasma etching were made. Both showed stable thermal properties over 300 degrees C. The proposed 3D electrode microarray of MWCNT/Nafion nanocomposites with micro-porous structures can be applied to miniaturized fuel cell devices.

Chemiluminescence determination of moxifloxacin in pharmaceutical and biological samples based on its enhancing effect of the luminol-ferricyanide system using a microfluidic chip.

A sensitive determination of a synthetic fluoroquinolone antibacterial agent, moxifloxacin (MOX), by an enhanced chemiluminescence (CL) method using a microfluidic chip is described. The microfluidic chip was fabricated by a soft-lithographic procedure using polydimethyl siloxane (PDMS). The fabricated PDMS microfluidic chip had three-inlet microchannels for introducing the sample, chemiluminescent reagent and oxidant, and a 500 µm wide, 250 µm deep and 82 mm long microchannel. An enhanced CL system, luminol-ferricyanide, was adopted to analyze the MOX concentration in a sample solution. CL light was emitted continuously after mixing luminol and ferricyanide in the presence of MOX on the PDMS microfluidic chip. The amount of MOX in the luminol-ferricyanide system influenced the intensity of the CL light. The linear range of MOX concentration was 0.14-55.0 ng/mL with a correlation coefficient of 0.9992. The limit of detection (LOD) and limit of quantification (LOQ) were 0.06 and 0.2 ng/mL respectively. The presented method afforded good reproducibility, with a relative standard deviation (RSD) of 1.05% for 10 ng/mL of MOX, and has been successfully applied for the determination of MOX in pharmaceutical and biological samples.

Cell chip device for real-time monitoring of drug release from drug-laden microparticles.

A cell chip is a microfluidic cell culture device fabricated using microchip manufacturing methods for culturing living cells in a micrometer-sized chamber to model the physiological functions of tissues and organs. It has been extensively investigated in the domain of drug transport and toxicity research. Herein, we developed a cell chip for real-time monitoring of drug release from drug carriers. The proposed system integrates three core functions: cell culture, real-time analysis, and drug delivery tests. This device was designed to be loaded with microparticles for drug release and to enable real-time drug measurement. The efficacy of the developed system was evaluated by measuring the concentration of drugs released from the microparticles prepared with poly(lactic-co-glycolic acid) (PLGA). Doxorubicin, an anticancer drug, was used as a model drug and A549 cells, a type of lung cancer cell, were simultaneously cultured to compare the drug release concentrations in the presence of cells. Furthermore, variations in cell viability with respect to the presence of drug-loaded microparticles were observed and analyzed. Notably, as the proposed system requires an extremely small number of microparticles, it affords simple implementation in a single device, thereby eliminating the need for complex accessories and instruments for analysis. Thus, the analysis process becomes more convenient and cost-efficient. Thus, the proposed method offers an easy analysis of the release behavior of various cells and drugs. The simplicity and low cost of this innovative system without sacrificing analytical precision demonstrate its potential for applications across various fields.

Chemiluminescence microfluidic system of gold nanoparticles enhanced luminol-silver nitrate for the determination of vitamin B12.

A rapid and sensitive chemiluminescence (CL) system coupled with a microfluidic chip has been presented to determine vitamin B12 (VB12) based on the reaction of luminol and silver nitrate (AgNO(3)) in the presence of gold nanoparticles (AuNPs). A microfluidic chip was fabricated by a soft-lithographic procedure using polydimethyl siloxane (PDMS) having four inlets and one outlet with a 200 µm wide, 250 µm deep, and 100 mm long microchannel. Ag(+) was used as a chemiluminogenic oxidant in this CL reaction which oxidized luminol to produce strong CL signal in the presence of AuNPs. Luminol reacted with AgNO(3) under the catalysis of AuNPs to produce luminol radicals which reacted with dissolved oxygen and emitted CL light. The proposed CL system was applied to determine the amount of VB12 in VB12 tablets and multivitamin. Under the optimum conditions, the CL intensity of the system was increased with the concentration of VB12 in the range of 0.25-100 ng mL(-1) with the correlation coefficient of 0.9982. The limit of detection was found to be 0.04 ng mL(-1) with the relative standard deviation of 1.56 % for five replicate determinations of 25 ng mL(-1) of VB12. The CL reaction mechanism was demonstrated by UV-visible spectra and CL emission spectra.

Enzymeless determination of total sugar by luminol-tetrachloroaurate chemiluminescence on chip to analyze food samples.

Chemiluminescence (CL) emission from luminol-tetrachloroaurate ([AuCl(4)](-)) system studied in presence of monosaccharide sugars such as glucose and fructose was investigated on a microfluidic chip fabricated by the soft lithography technique. CL emission from the luminol-[AuCl(4)](-) system at 430 nm was intensified remarkably by the catalytic activity of glucose and fructose at room temperature. Under optimized conditions, the CL emission intensity of the system was found to be linearly related to the concentration of the sugars. Based on this observation, nonenzymatic determination of total sugar (glucose, fructose, or hydrolyzable sucrose) was performed in a rapid and sensitive analytical method. The results revealed that the linearity ranged from 9 to 1,750 µM for glucose and 80 to 1,750 µM for fructose, with a limit of detection of 0.65 and 0.69 µM, respectively. The relative standard deviations determined at 250 µM based on six repetitive injections were 1.13 and 1.15% for glucose and fructose, respectively. The developed method was successfully applied for determination of the total sugar concentration in food and beverages.

Development of In Situ Microfluidic System for Preparation of Controlled Porous Microsphere for Tissue Engineering.

In this study, we present an in situ microfluidic system to precisely control highly porous polycaprolactone microspheres as tissue templates for tissue engineering. The porosity of the microspheres was controlled by adjusting the flow rates of the polymer phase and the pore-generating material phase in the dispersed phase. The microfluidic flow-focusing technique was adopted to manufacture porous microspheres using a relatively highly viscous polymer solution, and the device was fabricated by conventional photolithography and PDMS casting. The fabricated in situ microfluidic system was used to precisely control the pore size of monodispersed polycaprolactone microspheres. The porous microspheres with controlled pore sizes were evaluated by culturing HDF cells on the surface of porous microspheres and injection into the subcutaneous tissue of rats. We found that the increased pore size of the microspheres improved the initial proliferation rate of HDF cells after seeding and relieved the inflammatory response after the implantation of porous microspheres in the subcutaneous tissue of rats.

Deep learning-based optimization of a microfluidic membraneless fuel cell for maximum power density via data-driven three-dimensional multiphysics simulation.

A deep learning-based method for optimizing a membraneless microfluidic fuel cell (MMFC)performance by combining the artificial neural network (ANN) and genetic algorithm (GA) was for the first time introduced. A three-dimensional multiphysics model that had an accuracy equivalent to experimental results (R2 = 0.976) was employed to generate the ANN's training data. The constructed ANN is equivalent to the simulation (R2 = 0.999) but with far better computation resource efficiency as the ANN's execution time is only 0.041 s. The ANN model is then used by the GA to determine the inputs (microchannel length = 10.040 mm, width = 0.501 mm, height = 0.635 mm; temperature = 288.210 K, cell voltage = 0.309 V) that lead to the maximum power density of 0.263 mWcm-2 (current density of 0.852 mAcm-2) of the MMFC. The ANN-GA and numerically calculated maximum power densities differed only by 0.766%.

Development of a Subpath Extrusion Tip and Die for Peripheral Inserted Central Catheter Shaft with Multi Lumen.

The tip and die for manufacturing multi-lumen catheter tubes should be designed considering the flow velocity of the molten polymer and the deformation of the final extruded tube. In this study, to manufacture non-circular double-lumen tubes for peripherally inserted central catheters (PICCs), three types of tip and die structures are proposed. The velocity field and swelling effect when the circular tip and die (CTD) are applied, which is the commonly used tip and die structure, are analyzed through numerical calculation. To resolve the wall and rib thickness and ovality issues, the ellipse tip and die (ETD) and sub-path tip and die (STD) were proposed. In addition, based on the results of numerical analysis, the tip and die structures were manufactured and used to perform extrusion. Finally, we manufactured tubes that satisfied the target diameter, ovality, wall, and rib thickness using the newly proposed STD.

512-Channel Geometric Droplet-Splitting Microfluidic Device by Injection of Premixed Emulsion for Microsphere Production.

We present a 512-channel geometric droplet-splitting microfluidic device that involves the injection of a premixed emulsion for microsphere production. The presented microfluidic device was fabricated using conventional photolithography and polydimethylsiloxane casting. The fabricated microfluidic device consisted of 512 channels with 256 T-junctions in the last branch. Five hundred and twelve microdroplets with a narrow size distribution were produced from a single liquid droplet. The diameter and size distribution of prepared micro water droplets were 35.29 µm and 8.8% at 10 mL/h, respectively. Moreover, we attempted to prepare biocompatible microspheres for demonstrating the presented approach. The diameter and size distribution of the prepared poly (lactic-co-glycolic acid) microspheres were 6.56 µm and 8.66% at 10 mL/h, respectively. To improve the monodispersity of the microspheres, we designed an additional post array part in the 512-channel geometric droplet-splitting microfluidic device. The monodispersity of the microdroplets prepared with the microfluidic device combined with the post array part exhibited a significant improvement.

Continuous Determination of Glucose Using a Membraneless, Microfluidic Enzymatic Biofuel Cell.

In this article, we describe an enzyme-based, membraneless, microfluidic biofuel cell for the continuous determination of glucose using electrochemical power generation as a transducing signal. Enzymes were immobilized on multi-walled carbon nanotube (MWCNT) electrodes placed parallel to the co-laminar flow in a Y-shaped microchannel. The microchannel was produced with polydimethylsiloxane (PDMS) using soft lithography, while the MWCNT electrodes were replicated via a PDMS stencil on indium tin oxide (ITO) glass. Moreover, the electrodes were modified with glucose oxidase and laccase by direct covalent bonding. The device was studied at different MWCNT deposition amounts and electrolyte flow rates to achieve optimum settings. The experimental results demonstrated that glucose could be determined linearly up to a concentration of 4 mM at a sensitivity of 31 mV∙mM-1cm-2.

Smart Microneedles with Porous Polymer Layer for Glucose-Responsive Insulin Delivery.

A closed-loop system imitating the function of pancreatic cells, connected to microneedles (MNs) that automatically "release" insulin in response to the blood glucose (BG) levels would be highly satisfactory for improving the quality of life and health for diabetes patients. This paper describes an easy, fast and simple technique of coating a porous polymer layer on stainless steel (SS) MNs that release insulin in a glucose-responsive fashion. It was fabricated by sealing insulin, sodium bicarbonate (a pH-sensitive element [NaHCOз]) and glucose oxidase (glucose-specific enzymes [GOx]) into the pores of a porous polymer coating. Glucose can passively diffuse into the pores and become oxidized to gluconic acid by GOx, thereby causing a decrease in local pH. The subsequent reaction of protons with NaHCOз forms carbon dioxide (CO2) which creates pressure inside the pores, thereby rupturing the thin polymer film and releasing the encapsulated insulin. Field emission scanning electron microscopy (FE-SEM) images displayed that upon the exposure of MNs to glucose-free phosphate buffer saline (PBS) with pH 7.4, the pores of the porous MNs were closed, while in MNs exposed to a hyperglycemic glucose level, the pores were opened and the thin film burst. These MNs demonstrated both in vitro (in porcine skin and PBS) and in vivo (in diabetic rats) glucose-mediated insulin release under hyperglycemic conditions with rapid responsiveness. This study validated that the release of insulin from porous MNs was effectively correlated with glucose concentration.

Fabrication and Performance Evaluation of the Helmholtz Resonator Inspired Acoustic Absorber Using Various Materials.

A soundwave is transmitted by adjacent molecules in the medium, and depending on the type of sound, it exhibits various characteristics such as frequency, sound pressure, etc. If the acoustic wavelength of the soundwave is sufficiently long compared with the size of an acoustic element, physical analysis within the sound element could be simplified regardless of the shape of the acoustic element: this is called "long wavelength approximation". A Helmholtz resonator, a representative acoustic element which satisfies the "long wavelength theory", consists of a neck part and a cavity part. The Helmholtz resonators can absorb certain frequencies of sound through resonance. To exhibit attenuation properties at ultrasound range, the Helmholtz resonator should be made into a microscale since Helmholtz resonators should satisfy the "long wavelength approximation". In this study, Helmholtz resonator inspired acoustic elements were fabricated using MEMS technology, and acoustic attenuation experiments in a water bath were conducted using various shapes and materials. As a result, the fabricated samples showed admirable attenuation properties up to ~13 dB mm-1 at 1 MHz. The results were analyzed to derive the necessary conditions for the fabrication of acoustic elements with acoustic attenuation properties in ultrasound range.

Fabrication of 512-Channel Geometrical Passive Breakup Device for High-Throughput Microdroplet Production.

We present a 512-microchannel geometrical passive breakup device for the mass production of microdroplets. The mass production is achieved through the passive breakup of a droplet into two droplets. The microchannel geometry in the microfluidic device was designed and optimized by focusing on stable droplet splitting for microdroplet preparation and minimizing the hydraulic resistance of the microchannel for achieving high throughput; the minimization of hydraulic resistance was achieved by employing analytical approaches. A total of 512 microdroplets could be prepared from a single liquid plug by making the liquid plug pass through nine sequential T-junctions in the microfluidic device, which led to the splitting of droplets. The microfluidic device was fabricated using conventional photolithography and polydimethylsiloxane (PDMS) casting. We estimated the performance of the microfluidic device in terms of the size distribution and production rate of microdroplets. Microdroplets with a diameter of 40.0 ± 2.2 µm were prepared with a narrow size distribution (coefficient of variation (CV) < 5.5%) for flow rates of disperse (Qd) and continuous phase (Qc) of 2 and 3 mL/h, respectively. Microdroplet production rates were measured using a high-speed camera. Furthermore, monodisperse microdroplets were prepared at 42.7 kHz for Qd and Qc of 7 and 15 mL/h, respectively. Finally, the feasibility of the fabricated microfluidic device was verified by using it to prepare biodegradable chitosan microspheres.

Smart Microneedles with Porous Polymer Coatings for pH-Responsive Drug Delivery.

: This work demonstrates a simple approach for coating a porous polymer layer on stainless-steel (SS) microneedles characterized by a pH-responsive formulation for self-regulated drug delivery. For many drug-delivery applications, the release of therapeutic agents in an acidic microenvironment is desirable. Acid-sensitive polymers and hydrogels were extensively explored, but easily prepared polymeric microcarriers that combine acid sensitivity and biodegradability are rare. Here, we describe a simple and robust method of coating a porous polymer layer on SS microneedles (MNs) that release a model drug (lidocaine) in a pH-responsive fashion. It was constructed by packing the model drug and a pH-sensitive component (sodium bicarbonate) into the pores of the polymer layer. When this acid-sensitive formulation was exposed to the acidic microenvironment, the consequent reaction of protons (H+) with sodium bicarbonate (NaHCO3) yielded CO2. This effect generated pressure inside the pores of the coating and ruptured the thin polymer membrane, thereby releasing the encapsulated drug. Scanning electron micrographs showed that the pH-sensitive porous polymer-coated MNs exposed to phosphate-buffered saline (PBS) at pH 7.4 were characterized by closed pores. However, MNs exposed to PBS at pH 5.5 consisted of open pores and the thin membrane burst. The in vitro studies demonstrated the pH sensitivity of the drug release from porous polymer-coated MNs. Negligible release was observed for MNs in receiving media at pH 7.4. In contrast, significant release occurred when the MNs were exposed to acidic conditions (pH 5.5). Additionally, comparable results were obtained for drug release in vitro in porcine skin and in PBS. This revealed that our developed pH-responsive porous polymer-coated MNs could potentially be used for the controlled release of drug formulations in an acidic environment. Moreover, the stimuli-responsive drug carriers will enable on-demand controlled release profiles that may enhance therapeutic effectiveness and reduce systemic toxicity.

Porous polymer coatings on metal microneedles for enhanced drug delivery.

We present a simple method to coat microneedles (MNs) uniformly with a porous polymer (PLGA) that can deliver drugs at high rates. Stainless steel (SS) MNs of high mechanical strength were coated with a thin porous polymer layer to enhance their delivery rates. Additionally, to improve the interfacial adhesion between the polymer and MNs, the MN surface was modified by plasma treatment followed by dip coating with polyethyleneimine, a polymer with repeating amine units. The average failure load (the minimum force sufficient for detaching the polymer layer from the surface of SS) recorded for the modified surface coating was 25 N, whereas it was 2.2 N for the non-modified surface. Calcein dye was successfully delivered into porcine skin to a depth of 750 µm by the porous polymer-coated MNs, demonstrating that the developed MNs can pierce skin easily without deformation of MNs; additional skin penetration tests confirmed this finding. For visual comparison, rhodamine B dye was delivered using porous-coated and non-coated MNs in gelatin gel which showed that delivery with porous-coated MNs penetrate deeper when compared with non-coated MNs. Finally, lidocaine and rhodamine B dye were delivered in phosphate-buffered saline (PBS) medium by porous polymer-coated and non-coated MNs. For rhodamine B, drug delivery with the porous-coated MNs was five times higher than that with the non-coated MNs, whereas 25 times more lidocaine was delivered by the porous-coated MNs compared with the non-coated MNs.