Development of a novel self-sanitizing mask prototype to combat the spread of infectious disease and reduce unnecessary waste.

With the spread of COVID-19, significant emphasis has been placed on mitigation techniques such as mask wearing to slow infectious disease transmission. Widespread use of face coverings has revealed challenges such as mask contamination and waste, presenting an opportunity to improve the current technologies. In response, we have developed the Auto-sanitizing Retractable Mask Optimized for Reusability (ARMOR). ARMOR is a novel, reusable face covering that can be quickly disinfected using an array of ultraviolet C lamps contained within a wearable case. A nanomembrane UVC sensor was used to quantify the intensity of germicidal radiation at 18 different locations on the face covering and determine the necessary exposure time to inactivate SARS-CoV-2 in addition to other viruses and bacteria. After experimentation, it was found that ARMOR successfully provided germicidal radiation to all areas of the mask and will inactivate SARS-CoV-2 in approximately 180 s, H1N1 Influenza in 130 s, and Mycobacterium tuberculosis in 113 s, proving that this design is effective at eliminating a variety of pathogens and can serve as an alternative to traditional waste-producing disposable face masks. The accessibility, ease of use, and speed of sanitization supports the wide application of ARMOR in both clinical and public settings.

A novel print-and-release method to prepare microplastics using an office-grade laserjet printer; a low-cost solution for preliminary studies.

Microscopic plastic particles (microplastics) are widespread anthropogenic contaminants that are impacting aquatic ecosystems. Among the five most prevalent types of microplastics (polystyrene, polyamide, polyvinyl chloride, polyethylene, and polypropylene) in aquatic environments, the impact of polystyrene, polyethylene, and polypropylene has drawn more attention due to their high transportability. A lack of reliable inexpensive methods to accurately replicate the realistic microplastic samples extracted from environmental matrixes with the desired size and geometry is one of the main challenges in the design of experiments for systematic studies. In this work, a novel print-and-release technique to prepare colored microplastic (polystyrene) particles with a desired size and shape by using an office-grade laserjet printer is introduced. Microplastics ranging from 125 µm to 500 µm could be prepared with an average dimensional error of less than 5%. Their physical and chemical characteristics were obtained by SEM, FTIR, and XPS analyses.

A Novel Bismuth-Chitosan Nanocomposite Sensor for Simultaneous Detection of Pb(II), Cd(II) and Zn(II) in Wastewater.

A novel bismuth (Bi)-biopolymer (chitosan) nanocomposite screen-printed carbon electrode was developed using a Bi and chitosan co-electrodepositing technique for detecting multiple heavy metal ions. The developed sensor was fabricated with environmentally benign materials and processes. In real wastewater, heavy metal detection was evaluated by the developed sensor using square wave anodic stripping voltammetry (SWASV). The nanocomposite sensor showed the detection limit of 0.1 ppb Zn2+, 0.1 ppb Cd2+ and 0.2 ppb Pb2+ in stock solutions. The improved sensitivity of the Bi-chitosan nanocomposite sensor over previously reported Bi nanocomposite sensors was attributed to the role of chitosan. When used for real wastewater samples collected from a mining site and soil leachate, similar detection limit values with 0.4 ppb Cd2+ and 0.3 ppb Pb2+ were obtained with relative standard deviations (RSD) ranging from 1.3% to 5.6% (n = 8). Temperature changes (4 and 23 °C) showed no significant impact on sensor performance. Although Zn2+ in stock solutions was well measured by the sensor, the interference observed while detecting Zn2+ in the presence of Cu2+ was possibly due to the presence of Cu-Zn intermetallic species in mining wastewater. Overall, the developed sensor has the capability of monitoring multiple heavy metals in contaminated water samples without the need for complicated sample preparation or transportation of samples to a laboratory.

A Rapid In-Situ Electrochemical Surface Modification Process for Nanotextured Gold Electrodes.

Due to its unique physical and chemical properties, gold has been widely applied as electrode material for various applications. In recent years, with the increasing requirement on the electrode performance, researchers attempted to involve nanostructures into the electrode through various routes, which demonstrated the performance improvement but still are limited by the process complexity, toxic agents and high cost. In this work, a simple and fast electrochemical surface modification process of gold electrodes was developed. Compared with commonly used nanostructured gold electrode synthesis or modification processes, this In-Situ electrochemical modification process is based on electrochemical migration phenomenon and can be completed in short time (<90 seconds) without using caustic chemicals. It is hypothesized that this high efficiency formation mechanism is based on electrochemical dissolution of cations from and redeposition to the electrode surface. The evolution of nanostructures from nanopores under low current density processing conditions to nanodendrites under high current density conditions was observed.

Picomolar Detection of Hydrogen Peroxide using Enzyme-free Inorganic Nanoparticle-based Sensor.

A philosophical shift has occurred in the field of biomedical sciences from treatment of late-stage disease symptoms to early detection and prevention. Ceria nanoparticles (CNPs) have been demonstrated to neutralize free radical chemical species associated with many life-threatening disease states such as cancers and neurodegenerative diseases by undergoing redox changes (Ce3+ ↔ Ce4+). Herein, we investigate the electrochemical response of multi-valent CNPs in presence of hydrogen peroxide and demonstrate an enzyme-free CNP-based biosensor capable of ultra-low (limit of quantitation: 0.1 pM) detection. Several preparations of CNPs with varying Ce3+:Ce4+ are produced and are analyzed by electrochemical methods. We find that an increasing magnitude of response in cyclic voltammetry and chronoamperometry correlates with increasing Ce4+ relative to Ce3+ and utilize this finding in the design of the sensor platform. The sensor retains sensitivity across a range of pH's and temperatures, wherein enzyme-based sensors will not function, and in blood serum: reflecting selectivity and robustness as a potential implantable biomedical device.

A Graphene-Based Nanosensor for In Situ Monitoring of Polycyclic Aromatic Hydrocarbons (PAHs).

A graphene-based nanosensor was developed for in situ monitoring of polycyclic aromatic hydrocarbons (PAHs) in aqueous solutions. The sensor was fabricated using photolithography and etching of Au/Ti film on a silicon wafer followed by the transfer of a single graphene layer which was prepared separately by chemical vapor deposition (CVD). The performance of the graphene nanosensor was characterized using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The graphene-based sensor demonstrated a fast (<10 sec) and linear response to toluene (0 to 17 ppm) at +400 mV versus Ag/AgCl when measured amperometrically. The novelty can be found in utilizing high affinity of graphene to PAHs and intermolecular electron delocalization at the interface of graphene and a benzene ring for toluene detection in water. The developed sensor is applicable to many contaminated water bodies or engineered systems due to its reduced sensing cost, portability, and ease of use.

Graphene-P(VDF-TrFE) multilayer film for flexible applications.

A flexible, transparent acoustic actuator and nanogenerator based on graphene/P(VDF-TrFE)/graphene multilayer film is demonstrated. P(VDF-TrFE) is used as an effective doping layer for graphene and contributes significantly to decreasing the sheet resistance of graphene to 188 ohm/sq. The potentiality of graphene/P(VDF-TrFE)/graphene multilayer film is realized in fabricating transparent, flexible acoustic devices and nanogenerators to represent its functionality. The acoustic actuator shows good performance and sensitivity over a broad range of frequency. The output voltage and the current density of the nanogenerator are estimated to be ∼3 V and ∼0.37 µAcm(-2), respectively, upon the application of pressure. These values are comparable to those reported earlier for ZnO- and PZT-based nanogenerators. Finally, the possibility of rollable devices based on graphene/P(VDF-TrFE)/graphene structure is also demonstrated under a dynamic mechanical loading condition.

Laser irradiated nano-architectured undoped tin oxide arrays: mechanism of ultrasensitive room temperature hydrogen sensing.

Undoped nanostructured tin oxide (SnO(2)) arrays were prepared on oxidized Si substrates by nanosecond pulsed laser interference irradiation for hydrogen gas sensing applications. Scanning electron microscopy (SEM), in combination with Atomic Force Microscopy (AFM), showed that the SnO(2) surface consisted of periodic features of ∼130 nm width, ∼228 nm spacing, an average height of ∼8 nm along the periodicity and tens of microns length. The SnO(2) nanostructured arrays and precursor thin films were tested by cyclic exposure under dynamic conditions of hydrogen in the concentration range of 300-9000 ppm. The observed electrical response of SnO(2) towards hydrogen at low concentrations and room temperature drastically improved in the nanostructured array as compared to the thin film. The results suggest that this method to fabricate SnO(2) nanostructured arrays has the potential to produce nanodevices that have ultra-low detection limits, and fast response and recovery times, which are suited for practical hydrogen sensing applications.

Surface modification of carbon post arrays by atomic layer deposition of ZnO film.

The applicability of atomic layer deposition (ALD) process to the carbon microelectromechanical system technology was studied for a surface modification method of the carbon post electrodes. A conformal coating of the ALD-ZnO film was successfully demonstrated on the carbon post arrays which were fabricated by the traditional photolithography and subsequent two-step pyrolysis. A significant Zn diffusion into the underlying carbon posts was observed during the ALD process. The addition of a sputter-deposited ZnO interfacial layer efficiently blocked the Zn diffusion without altering the microstructure and surface morphology of the ALD-ZnO film.

Wettability control and flow regulation using a nanostructure-embedded surface.

This work addresses the synthesis, integration and characterization of a nanostructure-embedded thermoresponsive surface for flow regulation. In order to create a hierarchic structure which consists of microscale texture and nanoscale sub-texture, hybrid multilayers consisting of poly(allylamine hydrochloride) (PAH), poly(acrylic acid) (PAA) and colloidal silica nanoparticles (average diameter = 22 nm and 7 nm) were used. Based on the electrostatic interactions between the polyelectrolytes and nanoparticles, a layer-by-layer deposition technique in combination with photolithography was employed to obtain a localized, conformally-coated patch in a microchannel. Grafted with the thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAAm), wettability of the surface could be tuned upon heating or cooling. The measurement of differential pressure at various stages of device verified the working conditions of the nanostructure-embedded surface for regulating a capillary flow in the microchannel.

Graphene-based bimorph microactuators.

A novel graphene-on-organic film fabrication method that is compatible with a batch microfabrication process was developed and used for electromechanically driven microactuators. A very thin layer of graphene sheets was monolithically integrated and the unique material characteristics of graphene including negative thermal expansion and high electrical conductivity were exploited to produce a bimorph actuation. A large displacement with rapid response was observed while maintaining the low power consumption. This enabled the successful demonstration of transparent graphene-based organic microactuators.

Impact of drops on the surface of immiscible liquids.

Impact of drops on the surface of an immiscible liquid is studied. We show that in addition to the commonly-observed lens structure at the air-liquid interface, drops released from critical heights above the target liquid can sustain the impact and at the end maintain a spherical ball-shape configuration above the surface despite undergoing large deformation. The existence of this metastable state of the drop above the free surface and its transition into the more stable submerged lens configuration at the air-liquid interface is investigated. The initial impact which induces the degree of submergence is critically related to the two distinct life paths of drops impinging upon a liquid surface.

Organic electrochemical transistor based immunosensor for prostate specific antigen (PSA) detection using gold nanoparticles for signal amplification.

We demonstrated a highly sensitive organic electrochemical transistor (OECT) based immunosensor with a low detection limit for prostate specific antigen/alpha1-antichymotrypsin (PSA-ACT) complex. The poly(styrenesulfonate) doped poly(3,4-ethylenedioxythiophene) (PEDOT:PSS) based OECT with secondary antibody conjugated gold nanoparticles (AuNPs) provided a detection limit of the PSA-ACT complex as low as 1pg/ml, as well as improved sensitivity and a dynamic range, due to the role of AuNPs in the signal amplification. The sensor performances were particularly improved in the lower concentration range where the detection is clinically important for the preoperative diagnosis and screening of prostate cancer. This result shows that the OECT-based immunosensor can be used as a transducer platform acceptable to the point-of-care (POC) diagnostic systems and demonstrates adaptability of organic electronics to clinical applications.

On-chip surface plasmon resonance sensor.

A novel on-chip micro SPR (surface plasmon resonance) sensor based on an optoelectronic platform has been developed. This research aims for a fully integrated SPR sensor system to achieve a miniaturized, high throughput sensor system. A novel method for design and fabrication of the solid state SPR sensor device has been investigated. The generation and detection of the SPR sensor signal from the proposed platform has been proved using a simulated binding experiment.

Effect of air-pressure on room temperature hydrogen sensing characteristics of nanocrystalline doped tin oxide MEMS-based sensor.

Nanocrystalline indium oxide (In2O3)-doped tin oxide (SnO2) thin film sensor has been sol-gel dip-coated on a microelectrochemical system (MEMS) device using a sol-gel dip-coating technique. Hydrogen (H2) at ppm-level has been successfully detected at room temperature using the present MEMS-based sensor. The room temperature H2 sensing characteristics (sensitivity, response and recovery time, and recovery rate) of the present MEMS-based sensor has been investigated as a function of air-pressure (50-600 Torr) with and without the ultraviolet (UV) radiation exposure. It has been demonstrated that, the concentration of the surface-adsorbed oxygen-ions (which is related to the sensor-resistance in air), the ppm-level H2, and the oxygen (O2) partial pressure are the three major factors, which determine the variation in the room temperature H2 sensing characteristics of the present MEMS-based sensor as a function of air-pressure.

Autostereoscopic three-dimensional display based on a micromirror array.

A novel approach for three-dimensional (3-D) display systems implemented with a micromirror array was proposed, designed, realized, and tested. The major advantages of this approach include the following: (1) micromirrors are reflective and hence achromatic (panchromatic), (2) a wide variety of displays can be used as image sources, and (3) time multiplexing can be introduced on top of space multiplexing to optimize the viewing zone arrangements. A two-view (left and right) 3-D autostereoscopic display system was first constructed. Left- and right-eye views in the forms of both still and motion 3-D scenes were displayed, and viewers were able to fuse the stereo information. A multiview (two left and two right) 3-D autostereoscopic display system was then simulated.