Inkjet-printed flexible planar Zn-MnO2 battery on paper substrate.

Energy storage devices (ESD) which are intended to power electronic devices, used in close contact of human skin, are desirable to be safe and non-toxic. In light of this requirement, Zn based energy storage devices seem to provide a viable pathway as they mostly employ aqueous based electrolytes which are safe and non-toxic in their functioning. Additionally, having a flexible ESD will play a crucial role as it will enable the ESD to conform to the varying shapes and sizes of wearable electronics which they energize. In this work, we have developed an inkjet-printed Zinc ion battery (IPZIB) with planar electrode configuration over bond paper substrate. Zn has been used as the negative electrode, MnO2 is used as the positive electrode with Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the active binder. Conducting tracks of reduced graphene oxide (rGO) are used to construct the current collector on the paper substrate. The fabricated IPZIB delivered a high discharge capacity of 300.14 mAh g-1 at a current density of 200 mA g-1. The energy density of the IPZIB is observed as 330.15 Wh kg-1 at a power density of 220 W kg-1 and retains an energy density of 94.36 Wh kg-1 at a high power density of 1650 W kg-1. Finally, we have demonstrated the capability of the IPZIB to power a LED at various bending and folding conditions which indicates its potential to be used in the next generation flexible and wearable electronic devices.

Effect of the Standardized ZnO/ZnO-GO Filter Element Substrate driven Advanced Oxidation Process on Textile Industry Effluent Stream: Detailed Analysis of Photocatalytic Degradation Kinetics.

A simple process of synthesizing coated filter element substrates (FES) containing zinc oxide (ZnO) nanorods and ZnO graphene-oxide nanocomposite for a pilot-scale industrial dye-effluent treatment plant is proposed. This work reports a detailed analysis of the photocatalysis mechanism on real industrial effluent streams containing a mixture of dyes. The analysis is very relevant for conducting advanced oxidation process-assisted effluent remediation at a field-level treatment operation. Estimation of the dye concentration shows nearly complete (≥98%) degradation from an initial dye sample concentration. A detailed study for the analysis of the initial reactive dyes and their degradation products was performed for quantification and identification of the degradation products through various spectral techniques. A design of the remediation mechanism through degradation pathways is proposed for characterizing the organic compounds in the degraded dye products. A regeneration and reusability study was performed on the FES presenting the durability of the FES-designed synthesis process originally for 11 cycles and regenerated FES for six cycles for achieving a threshold of 60% degradation efficiency. The experimental results demonstrate the efficacy of FES through the designed immobilized approach for the complete remediation of textile dye effluents for a 4 h treatment plant process and the consistent operability of the FES for the combined dye wastewater treatment operations.

Hybrid fractal acoustic metamaterials for low-frequency sound absorber based on cross mixed micro-perforated panel mounted over the fractals structure cavity.

The proposed work enumerates a hybrid thin, deep-subwavelength (2 cm) acoustic metamaterials acting as a completely new type of sound absorber, showing multiple broadband sound absorption effects. Based on the fractal distribution of Helmholtz resonator (HRs) structures, integrated with careful design and construct hybrid cross micro-perforated panel (CMPP) that demonstrate broad banding approximately one-octave low-frequency sound absorption behavior. To determine the sound absorption coefficient of this novel type of metamaterial, the equivalent impedance model for the fractal cavity and the micro-perforated Maa's model for CMPP are both used. We validate these novel material designs through numerical, theoretical, and experimental data. It is demonstrated that the material design possesses superior sound absorption which is primarily due to the frictional losses of the structure imposed on acoustic wave energy. The peaks of different sound absorption phenomena show tunability by adjusting the geometric parameters of the fractal structures like cavity thickness 't', cross perforation diameter of micro perforated panel, etc. The fractal structures and their perforation panel are optimized dimensionally for maximum broadband sound absorption which is estimated numerically. This new kind of fractals cavity integrated with CMPP acoustic metamaterial has many applications as in multiple functional materials with broad-band absorption behavior etc.

Integrated DEP Assisted Detection of PCR Products With Metallic Nanoparticle Labels Through Impedance Spectroscopy.

Electrochemical impedance spectroscopy (EIS) is gaining immense popularity in the current times due to the ease of integration with microelectronics. Keeping this aspect in mind, various detection schemes have been developed to make impedance detection of nucleic acids more specific. In this context, the current work makes a strong case for specific DNA detection through EIS using nanoparticle labeling approach and also an added selectivity step through the use of dielectrophoresis (DEP), which enhances the detection sensitivity and specificity to match the detection capability of quantitative polymerase chain reaction (qPCR) in real-time context as compared to the individually amplified DNA (Liu et al., 2008). The detection limit of the proposed biochip is observed to be 3-4 PCR cycles for 582 bp bacterial DNA, where the complete procedure of detection starts in less than 10 min. The process of integrated DEP capture of labeled products coming out of PCR and their impedance-assisted detection is carried out in an in-house micro-fabricated biochip. The gold nanoparticles, which possess excellent optical, chemical, electronic, and biocompatibility properties and are capable of generating lump-like DNA structure without modifying its basic impedance signature are introduced to the amplified DNA through the nanoparticle labeled primers.

Development of hydrophobic paper substrates using silane and sol-gel based processes and deriving the best coating technique using machine learning strategies.

Low energy surface coatings have found wide range of applications for generating hydrophobic and superhydrophobic surfaces. Most of the studies have been related to use of a single coating material over a single substrate or using a single technique. The degree of hydrophobicity is highly dependent on fabrication processes as well as materials being coated and as such warrants a high-level study using experimental optimization leading to the evaluation of the parametric behavior of coatings and their application techniques. Also, a single platform or system which can predict the required set of parameters for generating hydrophobic surface of required nature for given substrate is of requirement. This work applies the powerful machine learning algorithms (Levenberg Marquardt using Gauss Newton and Gradient methods) to evaluate the various processes affecting the anti-wetting behavior of coated printable paper substrates with the capability to predict the most optimized method of coating and materials that may lead to a desirable surface contact angle. The major application techniques used for this study pertain to dip coating, spray coating, spin coating and inkjet printing and silane and sol-gel base coating materials.

Evolving Paradigm of Prothrombin Time Diagnostics with Its Growing Clinical Relevance towards Cardio-Compromised and COVID-19 Affected Population.

Prothrombin time (PT) is a significant coagulation (hemostasis) biomarker used to diagnose several thromboembolic and hemorrhagic complications based on its direct correlation with the physiological blood clotting time. Among the entire set of PT dependents, candidates with cardiovascular ailments are the major set of the population requiring lifelong anticoagulation therapy and supervised PT administration. Additionally, the increasing incidence of COVID affected by complications in coagulation dynamics has been strikingly evident. Prolonged PT along with sepsis-induced coagulopathy (SIC score > 3) has been found to be very common in critical COVID or CAC-affected cases. Considering the growing significance of an efficient point-of-care PT assaying platform to counter the increasing fatalities associated with cardio-compromised and coagulation aberrations propping up from CAC cases, the following review discusses the evolution of lab-based PT to point of care (PoC) PT assays. Recent advances in the field of PoC PT devices utilizing optics, acoustics, and mechanical and electrochemical methods in microsensors to detect blood coagulation are further elaborated. Thus, the following review holistically aims to motivate the future PT assay designers/researchers by detailing the relevance of PT and associated protocols for cardio compromised and COVID affected along with the intricacies of previously engineered PoC PT diagnostics.

Textile-based supercapacitors for flexible and wearable electronic applications.

Electronic textiles have garnered significant attention as smart technology for next-generation wearable electronic devices. The existing power sources lack compatibility with wearable devices due to their limited flexibility, high cost, and environment unfriendliness. In this work, we demonstrate bamboo fabric as a sustainable substrate for developing supercapacitor devices which can easily integrate to wearable electronics. The work demonstrates a replicable printing process wherein different metal oxide inks are directly printed over bamboo fabric substrates. The MnO2-NiCo2O4 is used as a positive electrode, rGO as a negative electrode, and LiCl/PVA gel as a solid-state electrolyte over the bamboo fabrics for the development of battery-supercapacitor hybrid device. The textile-based MnO2-NiCo2O4//rGO asymmetric supercapacitor displays excellent electrochemical performance with an overall high areal capacitance of 2.12 F/cm2 (1,766 F/g) at a current density of 2 mA/cm2, the excellent energy density of 37.8 mW/cm3, a maximum power density of 2,678.4 mW/cm3 and good cycle life. Notably, the supercapacitor maintains its electrochemical performance under different mechanical deformation conditions, demonstrating its excellent flexibility and high mechanical strength. The proposed strategy is beneficial for the development of sustainable electronic textiles for wearable electronic applications.

Micro/Nano fabricated cantilever based biosensor platform: A review and recent progress.

Recent trends in biosensing research have motivated scientists and research professionals to investigate the development of miniaturized bioanalytical devices to make them portable, label-free and smaller in size. The performance of the cantilever-based devices which is one of the very important domains of sensitive field level detection has improved significantly with the development of new micro/nanofabrication technologies and surface functionalization techniques. The cantilevers have scaled down to Nano from micro-level and have become exceptionally sensitive and also have some anomalous associated properties due to the scale. In this review we have discussed about fundamental principles of cantilever operation, detection methods, and previous, present and future approaches of study through cantilever-based sensing platform. Other than that, we have also discussed the past major bio-sensing efforts through micro/nano cantilevers and about recent progress in the field.

Synchronized Electromechanical Shock Wave-Induced Bacterial Transformation.

We report a simple device that generates synchronized mechanical and electrical pressure waves for carrying out bacterial transformation. The mechanical pressure waves are produced by igniting a confined nanoenergetic composite material that provides ultrahigh pressure. Further, this device has an arrangement through which a synchronized electric field (of a time-varying nature) is initiated at a delay of ≈85 µs at the full width half-maxima point of the pressure pulse. The pressure waves so generated are incident to a thin aluminum-polydimethylsiloxane membrane that partitions the ignition chamber from the column of the mixture containing bacterial cells (Escherichia coli BL21) and 4 kb transforming DNA. A combination of mechanical and electrical pressure pulse created through the above arrangement ensures that the transforming DNA transports across the cell membrane into the cell, leading to a transformation event. This unique device has been successfully operated for efficient gene (∼4 kb) transfer into cells. The transformation efficacy of this device is found comparable to the other standard methods and protocols for carrying out the transformation.

Poly-L-Lysine functionalised MWCNT-rGO nanosheets based 3-d hybrid structure for femtomolar level cholesterol detection using cantilever based sensing platform.

In this work we have developed a novel rGO-MWCNT (reduced graphene oxide-multiwalled carbon nanotube) nanocomposite material with Poly-L-Lysine functionalization which can be used for detection of biomolecules with enhanced sensitivity. The reduced GO sheets are found to play a major role as a connector and helps in the assembly of bundles of carbon nanotubes (CNTs) which may sometime play a role of upstanding nanostructures. The overall composite structure is further fully functionalized resulting in an overall high density of amino groups that can be used to capture biomolecules. The sensitivity of the as synthesized film is tested by the oxidation of cholesterol through cholesterol oxidase enzyme that is biochemically immobilized over these composite films. The test for the immobilization density of the novel films are carried out by mounting these films on sensitive thin section static micro/nano-cantilever platforms. The platforms have capability to measure cholesterol traces in blood upto an extent of 100 femto molar through deflection /bending of the cantilevers due to surface reaction. The films developed show a promise of high immobilization density which is further confirmed through fluorescence studies using FITC labeling of functionalized MWCNT-PLL and rGO-PLL films respectively.

Tapered lateral flow immunoassay based point-of-care diagnostic device for ultrasensitive colorimetric detection of dengue NS1.

Dengue virus, a Flaviviridae family member, has emerged as a major worldwide health concern, making its early diagnosis imperative. Lateral flow immunoassays have been widely employed for point-of-care diagnosis of dengue because of their rapid naked eye readouts, ease of use, and cost-effectiveness. However, they entail a drawback of low sensitivity, limiting their usage in clinical applications. Herein, we report a novel lateral flow immunoassay for detection of dengue leveraging on the benefits of gold decorated graphene oxide sheets as detection labels and a tapered nitrocellulose membrane. The developed assay allows for rapid (10 min) and sensitive detection of dengue NS1 with a detection limit of 4.9 ng mL-1, ∼11-fold improvement over the previously reported values. Additionally, the clinical application of the developed assay has been demonstrated by testing it for dengue virus spiked in human serum. The reported lateral flow immunoassay shows significant promise for early and rapid detection of several target diseases.

Inkjet-Printed Electrodes on A4 Paper Substrates for Low-Cost, Disposable, and Flexible Asymmetric Supercapacitors.

Printed electronics is widely gaining much attention for compact and high-performance energy-storage devices because of the advancement of flexible electronics. The development of a low-cost current collector, selection, and utilization of the proper material deposition tool and improvement of the device energy density are major challenges for the existing flexible supercapacitors. In this paper, we have reported an inkjet-printed solid-state asymmetric supercapacitor on commercial A4 paper using a low-cost desktop printer (EPSON L130). The physical properties of all inks have been carefully optimized so that the developed inks are within the printable range, i.e., Fromm number of 4 < Z < 14 for all inks. The paper substrate is made conducting (sheet resistance ∼ 1.6 Ω/sq) by printing 40 layers of conducting graphene oxide (GO) ink on its surface. The developed conducting patterns on paper are further printed with a GO-MnO2 nanocomposite ink to make a positive electrode, and another such structure is printed with activated carbon ink to form a negative electrode. A combination of both of these electrodes is outlaid by fabricating an asymmetric supercapacitor. The assembled asymmetric supercapacitor with poly(vinyl alcohol) (PVA)-LiCl gel electrolyte shows a stable potential window of 0-2.0 V and exhibits outstanding flexibility, good cyclic stability, high rate capability, and high energy density. The fabricated paper-substrate-based flexible asymmetric supercapacitor also displays an excellent electrochemical performances, e.g., a maximum areal capacitance of 1.586 F/cm2 (1023 F/g) at a current density of 4 mA/cm2, highest energy density of 22 mWh/cm3 at a power density of 0.099 W/cm3, a capacity retention of 89.6% even after 9000 charge-discharge cycles, and a low charge-transfer resistance of 2.3 Ω. So, utilization of inkjet printing for the development of paper-based flexible electronics has a strong potential for embedding into the next generation low-cost, compact, and wearable energy-storage devices and other printed electronic applications.

Impact of surface roughness on Dielectrophoretically assisted concentration of microorganisms over PCB based platforms.

This article presents a PCB based microfluidic platform for performing a dielectrophoretic capture of live microorganisms over inter-digitated electrodes buried under layers of different surface roughness values. Although dielectrophoresis has been extensively studied earlier over silicon and polymer surfaces with printed electrodes the issue of surface roughness particularly in case of buried electrodes has been seldom investigated. We have addressed this issue through a layer of spin coated PDMS (of various surface roughness) that is used to cover the printed electrodes over a printed circuit board. The roughness in the PDMS layer is generally defined by the roughness of the FR4 base which houses the printed electrodes as well as other structures. Possibilities arising out of COMSOL simulations have been well validated experimentally in this work.

Electricity from the silk cocoon membrane.

Silk cocoon membrane (SCM) is an insect engineered structure. We studied the electrical properties of mulberry (Bombyx mori) and non-mulberry (Tussar, Antheraea mylitta) SCM. When dry, SCM behaves like an insulator. On absorbing moisture, it generates electrical current, which is modulated by temperature. The current flowing across the SCM is possibly ionic and protonic in nature. We exploited the electrical properties of SCM to develop simple energy harvesting devices, which could operate low power electronic systems. Based on our findings, we propose that the temperature and humidity dependent electrical properties of the SCM could find applications in battery technology, bio-sensor, humidity sensor, steam engines and waste heat management.

Integrated sorting, concentration and real time PCR based detection system for sensitive detection of microorganisms.

The extremely low limit of detection (LOD) posed by global food and water safety standards necessitates the need to perform a rapid process of integrated detection with high specificity, sensitivity and repeatability. The work reported in this article shows a microchip platform which carries out an ensemble of protocols which are otherwise carried in a molecular biology laboratory to achieve the global safety standards. The various steps in the microchip include pre-concentration of specific microorganisms from samples and a highly specific real time molecular identification utilizing a q-PCR process. The microchip process utilizes a high sensitivity antibody based recognition and an electric field mediated capture enabling an overall low LOD. The whole process of counting, sorting and molecular identification is performed in less than 4 hours for highly dilute samples.

High-performance nanothermite composites based on aloe-vera-directed CuO nanorods.

In this work, we demonstrate the development of high-performance nanothermite composites derived from super-reactive CuO nanorods oxidizers fabricated by simple biogenic routes using Aloe vera plant extracts. Nanorods of various length scales have been realized via simple sonoemulsion and solid-state biosynthesis routes using Aloe vera gel as a green surfactant promoting the directional growth of CuO nanorods in both solid and emulsion phase. The biosynthesized CuO nanorods (oxidizers)/fuel (nanoaluminum) composites ignited vigorously with abundant gas generation, developing high heat of reaction of 1.66 kJ g(-1) and very high pressurization rate of around 1.09 MPa µs(-1) and peak pressure of 65.4 MPa when blasted inside a constant volume pressure cell with a charge density of 0.2 g cm(-3). The pressurization rates so obtained are four times higher with twice the peak pressure in comparison to such nanothermites formulated via other available state of the art wet-chemical techniques, which reflects the catalytic role of Aloe vera surface functional groups (A. vera-sfg) enhancing the reactivity of CuO oxidizers with excess gas release rate during exothermic reaction with nanoaluminum. Through this work, Aloe vera gel has for the first time been identified as a novel biotemplate for green synthesis of nanorod structures of metal oxides, and we have also studied the utility of A. vera-sfg in the creation of super-reactive CuO oxidizers producing excellent heat of reaction and dynamic pressure characteristics as demanded in propellants, explosives, and pyrotechnics.

A microfluidic cell trap device for automated measurement of quantal catecholamine release from cells.

Neurons and endocrine cells secrete neurotransmitter and hormones in discrete packets in a process called quantal exocytosis. Electrochemical microelectrodes can detect spikes in current resulting from the oxidation of individual quanta of transmitter only if the electrodes are small and directly adjacent to release sites on the cell. Here we report development of a microchip device that uses microfluidic traps to automatically target individual or small groups of cells to small electrochemical electrodes. Microfluidic channels and traps were fabricated by multi-step wet etch of a silicon wafer whereas Pt electrodes were patterned in register with the trap sites. We demonstrate high-resolution amperometric measurement of quantal exocytosis of catecholamines from chromaffin cells on the device. This reusable device is a step towards developing high-throughput lab-on-a-chip instruments for recording quantal exocytosis to increase the pace of basic neuroscience research and to enable screening of drugs that target exocytosis.

Dielectrophoresis assisted concentration of micro-particles and their rapid quantitation based on optical means.

The detection and counting of micro particles having sizes comparable to biological entities can provide a tremendous impetus to rapid diagnostics and clinical applications. MEMS technology has already been used in capture and detection of such micron size entities in miniscule concentrations. For this purpose a concentration step is normally added prior to the detection process. A variety of methodologies are used for quantization of such micron size particles/entities including change in permittivity, medium impedance, magnetic permeability and other means. Although optical studies have been extensively performed prior to this, it has not been used for quantization of the micro particles. We have designed, developed and characterized a MEMS counter which captures micron size fluorescent beads using delectrophoresis (DEP) and monitors their accumulation in a 12 µm x 230 µm size channel and monitors this accumulation as growth of overall fluorescence. The field is generated by a set of finely placed interdigitated microelectrodes. As we apply an alternating voltage at 10 V(pp) for a range of different frequencies we are able to capture the flowing beads and concentrate them by several orders of magnitude. This is also followed by their quantification in terms of growing fluorescence signal. For quantitating the fluorescence values a CCD (charge couple device) module fitted over an inverted fluorescence microscope is used that visualizes the whole capture process and a Labview based image acquisition software simultaneously calculates the signal intensity over these frames and arranges it temporally. Our work will have tremendous utility in developing a rapid bacterial counting procedure and will be a valuable tool in microbiological laboratories.

Targeted capture of pathogenic bacteria using a mammalian cell receptor coupled with dielectrophoresis on a biochip.

Efficient capture of target analyte on biosensor platforms is a prerequisite for reliable and specific detection of pathogenic microorganisms in a microfluidic chip. Antibodies have been widely used as ligands; however, because of their occasional unsatisfactory performance, a search for alternative receptors is underway. Heat shock protein 60 (Hsp60), a eukaryotic mitochondrial chaperon protein is a receptor for Listeria adhesion protein (LAP) during Listeria monocytogenes infection. This paper reports application of biotinylated Hsp60 as a capture molecule for living (viable) L. monocytogenes in a microfluidic environment. Hsp60, immobilized on the surface of streptavidin-coated silicon dioxide exhibited specific capture of pathogenic Listeria against a background of other Listeria species, Salmonella, Escherichia, Bacillus, Pseudomonas, Serratia, Hafnia, Enterobacter, Citrobacter, and Lactobacillus. The capture efficiency of L. monocytogenes was 83 times greater than another Listeria receptor, the monoclonal antibody, mAb-C11E9. Additionally, the capture rate was further increased on a Hsp60-coated biochip by 60% when a dielectrophoresis force was applied for 5 min at the beginning of the final 1 h incubation step. Our data show that Hsp60 could be used for specific detection of L. monocytogenes on a biochip sensor platform.

Electrochemical Properties of Carbon Nanoparticles Entrapped in Silica Matrix.

Carbon-based electrode materials have been widely used for many years for electrochemical charge storage, energy generation, and catalysis. We have developed an electrode material with high specific capacitance by entrapping graphite nanoparticles into a sol-gel network. Films from the resulting colloidal suspensions were highly porous due to the removal of the entrapped organic solvents from sol-gel matrix giving rise to high Brunauer-Emmett-Teller (BET) specific surface areas (654 m(2)/g) and a high capacitance density ( approximately 37 F/g). An exponential increase of capacitance was observed with decreasing scan rates in cyclic voltammetry studies on these films suggesting the presence of pores ranging from micro (< 2 nm) to mesopores. BET surface analysis and scanning electron microscope images of these films also confirmed the presence of the micropores as well as mesopores. A steep drop in the double layer capacitance with polar electrolytes was observed when the films were rendered hydrophilic upon exposure to a mild oxygen plasma. We propose a model whereby the microporous hydrophobic sol-gel matrix perturbs the hydration of ions which moves ions closer to the graphite nanoparticles and consequently increase the capacitance of the film.