Table of contents

Over the past few decades, fabrication of optimal nanostructures for detecting specific bio-entities remained an active area of research. It is well-known that the structure and the plasmonic properties of noble metal nanoparticles can be customized for specific applications such as biosensing, diagnosis, imaging, etc. by tuning the size and shape of the nanoparticles. Thus, by using the plasmonic property of noble metals, the detection at the nano-scale is possible by monitoring the shift of Localized Surface Plasmon Resonance (LSPR) band with respect to the changes in the dielectric constant of the surrounding medium. The present study is aimed to the evaluation of the quality and performance of two nano plasmonic platforms for detection and capture of exosomes.

Due to the excellent biocompatibility of gold nanoparticles with human organism, they have great potentials for controlled drug delivery, cancer detection, cancer therapy, cancer management, and biomedical imaging. The unique optical and physiochemical properties of gold nanoparticles have made them a great candidate for intracellular diagnosis using surface-enhanced Raman microscopy and hyperspectral microscopy. These two techniques offer sensitive and non-invasive measurements. Gold nanoparticles also can be utilized to modulate the mechanobiological properties of cells, providing a platform to suppress the metastatic level of cells.

Micro-photosynthetic power cell (μPSC) is one of the emerging energy harvesting technologies which harvests energy using light (photosynthesis) and carbohydrate metabolism in dark (respiration) for low-power (mW range) applications. μPSC is a green technology that not only uses solar power and algae, but also provides power in both dark and light conditions. This perspective article provides state of the art of μPSC technology in terms of fabrication, mathematical modeling and energy harvesting circuit design. Currently, low power densities and high cost are the factors limiting μPSCs commercialization. Key aspects and methods to enhance the performance and decrease the cost are proposed in this paper.

Boron nitride quantum dots (BNQDs) were synthesized hydrothermally using boric acid and urea. High-resolution transmission electron microscopy (HR-TEM) analysis confirmed the formation of BN quantum dots with the lattice size of 0.227 nm. Fourier-transform infrared (FT-IR) and Ultraviolet–visible (UV-Vis) spectroscopies revealed the B-N, O-H and N-H bond formation in the BNQDs and the maximum absorption wavelength at 269 nm. BNQDs exhibited strong fluorescence emission at a wavelength of 330 nm. Furthermore, BNQDs were coated onto a glassy carbon electrode (GCE). Followed by, poly(luminol) (Plu) was electrochemically deposited onto BNQDs/GCE from 0.1 M H₂SO₄ containing 0.5 mM luminol in order to prepare nanocomposite (hybrid film) coated electrode with improved stability and electrochemical activity. Due to unique nature and synergetic effect between BNQDs and Poly(luminol), as-prepared hybrid Plu/BNQDs film coated GCE showed improved electrocatalytic activity for vitamin C (ascorbic acid, AA) oxidation at 0.2 V. The calibration graph was obtained from 10 to 100 μM AA by amperometry and limit of detection (LOD) was found to be 1.107 μM. The interference effects were also carried out in the presence of uric acid (UA), dopamine (DA) and glucose (Glu). Interestingly, UA, DA and Glu did not produce significant responses on the Plu/BNQDs/GCE which indicated good selectivity of the sensor for AA. Moreover, Plu/BNQDs/GCE based sensor showed reproducible and repeatable analytical performances. We propose that the Plu/BNQDs based hybrid film can be used as a selective sensor probe for the detection of the AA.

In vitro fabricated biological tissue would be a valuable tool to screen newly synthesized drugs or understand the tissue development process. However, controlling the growth and morphology of the fabricated tissue remains a challenge. Therefore, new techniques are required. Here we report a simple method to modify the surface of an ex-vivo culture substrate using unmodified chitosan solution. The effect of chitosan coating on the tissue culture plate and alginate hydrogel was evaluated. Fourier transform infrared spectroscopy (FT/IR), results demonstrated that there are no crosslinking reactions presents between chitosan and alginate. Data obtained from the in vitro study demonstrated the increase in the cell adhesion, proliferation and growth potential of the 0.3% chitosan-coated sample. In addition, when an isolated submandibular gland (SMG) was cultured on a 0.3% chitosan-coated alginate hydrogel sheet, SMG growth including bud expansion, and neural innervation was dramatically enhanced. This study is important for the assessment and design of surfaces for ex-vivo culture-based tissue engineering and it is possible to control the cell behavior by changing the chitosan concentration and employing fairly fast and reproducible simple coating technique. This also helps to design the new chitosan-based materials for different biological applications in the field of tissue engineering.

The automated identification of colors and their intensity from sensor images is a significant interest in field deployable and cost-effective smartphone-based water monitoring solutions. Artificial Intelligence (AI) has been extensively used in automated image processing applications specifically when there is no recognizable pattern in the image data. AI considerably outperforms conventional detection techniques using image analysis in such scenarios. In the present work, we have developed an Artificial Intelligence (AI) based mobile application platform, that can capture the sensor image using an inbuilt smartphone camera, identify the presence of sensing parameters and classify the level of the same based on color intensity recognized in the training sets of the captured image using deep convolutional neural networks (CNN). As a test case, we have implemented the developed AI-based mobile application platform to monitor the water quality for bacterial contamination where the sensor images are classified into the presence or absence of bacteria based on visual appearance. Our method is seen to detect the presence with a ∼99.99% accuracy which is an improvement in the detection accuracy of the already established method in this regard where manual visual inspection is carried out to classify the sensor images. The considerable enhancement in detection accuracy can be attributed to the elimination of subjective decision making which inevitable consequence of human intervention in the reported test case.

The article aims to optimize the inkjet printing properties to realize highly conductive and mechanically stable printed patterns on the Polyethylene terephthalate (PET) substrate. The key printing parameters such as drop spacing, the number of printed layers, and sintering temperatures were investigated. The test specimens were printed using silver nanoparticle ink and Dimatix 2831 inkjet printer. Then, the printed samples were characterized by electrical conductivity, bending, and adhesion tests. The Analysis of Variance (ANOVA) analysis showed that the number of layers and sintering temperatures were significant factors (p < 0.05) affecting electrical conductivity. The optimum printing parameters for the PET substrate were found to be 20 μm drop spacing, three layers of printing, and 120°C sintering temperature for 30 minutes. The measured optimum resistivity was found to be 5.25 μΩ-cm. The repetitive bending and adhesion test and ASTM tape test indicated good mechanical stability.

The optimization of the porosity and pore radius of ZnO for the application in dye-sensitized solar cells is essential to enhance the cell performance. Porous ZnO films were fabricated by electrodeposition in the presence of eosin Y or in combination with eosin B which was used as a structure directing agent (SDA) for the first time. The influence of the deposition time and the SDA concentration on film porosity and pore radius was characterized by a combined electrochemical and atomic absorption spectroscopy analysis, and confirmed by gas sorption, optical spectroscopy and scanning electron microscopy. The combination of eosin Y with eosin B as SDA results in porous ZnO films with larger pore radius compared to the films prepared with eosin Y only. The larger pores showed a significantly decreased diffusion impedance leading to an increased photocurrent less hindered by mass transport. Successful application of these new ZnO films in dye-sensitized solar cells confirmed improved pathways for large complex ions as redox shuttles through the ZnO pore structure.

In this study, prior to the growth of ZnO nanorods (NRs), a 100 nm-thick ZnO seed layer was deposited by RF magnetron sputtering on a glass substrate. Subsequently, ZnO NRs were grown on ZnO seed layers via the hydrothermal method at 90°C for 6 h and annealing at 400°C. By using a Pt electrode as reference electrode, the potentiometric method was used to measure the potential difference between the two ends, and an operation amplifier (OPA) was employed as the readout circuit. The sensor and reference electrode were placed in a buffer solution of different pH values (4, 6, 8, and 10) for potentiometric analysis. Results showed that the average sensitivity of the ZnO NR sensor was ∼4.4 × 10⁻² V/pH, and linearity was ∼0.98. The Arduino Uno was used to collect data, and the XBee module was utilized for wireless transmission. The computer side used the C# program to present the user interface, display the measurement results, and realize a wireless sensing network.

Three stochastic microsensors designed using matrices based on diamond, graphite and graphene decorated with Pt nanoparticles modified with 2,6-bis (E)-2-(thiophen-3-yl)-4-4-(4,6,8-trimethylazulen-1-1yl) pyridine and protoporphyrin IX (PIX) were designed, characterized and validated for the assay of: C-reactive protein, adiponectin and Zn²⁺. The working concentration ranges were for C-reactive protein: 2.04 × 10⁻⁸–1.00mg/mL when the stochastic microsensor based on 2,6-bis (E)-2-(thiophen-3-yl)-4-4-(4,6,8-trimethylazulen-1-1yl) pyridine and graphite was used, 8.20 × 10⁻⁸-0.52mg/mL when the stochastic microsensor based on 2,6-bis (E)-2-(thiophen-3-yl)-4-4-(4,6,8-trimethylazulen-1-1yl) pyridine and diamond paste was used, 1.64 × 10⁻⁸–0.41mg/mL when the stochastic microsensor based on protoporphyrin IX and graphene decorated with Pt nanoparticles was used, for adiponectin 2.50 × 10⁻⁸–1.00μg/mL when the stochastic microsensor based on 2,6-bis (E)-2-(thiophen-3-yl)-4-4-(4,6,8-trimethylazulen-1-1yl) pyridine and graphite was used, 2.50 × 10⁻⁸–0.25μg/mL when the stochastic microsensor based on 2,6-bis (E)-2-(thiophen-3-yl)-4-4-(4,6,8-trimethylazulen-1-1yl) pyridine and diamond paste was used, 2.50 × 10⁻⁸–0.25μg/mL when the stochastic microsensor based on protoporphyrin IX and graphene decorated with Pt nanoparticles was used, and for Zn²⁺: 1.36 × 10⁻¹⁰–1.00μg/mL when the stochastic microsensor based on 2,6-bis (E)-2-(thiophen-3-yl)-4-4-(4,6,8-trimethylazulen-1-1yl) pyridine and graphite was used, 1.36 × 10⁻⁸–1.00μg/mL when the stochastic microsensor based on 2,6-bis (E)-2-(thiophen-3-yl)-4-4-(4,6,8-trimethylazulen-1-1yl) pyridine and diamond paste was used, 1.36 × 10⁻⁸–1.00μg/mL when the stochastic microsensor based on protoporphyrin IX and graphene decorated with Pt nanoparticles was used. Very low limits of determination were recorded. The sensitivities of all tested stochastic microsensors were very high. The validation of the screening method for serum samples was done, high accuracy and precision being recorded.

Exciting discoveries in material science and molecular interactions are resulting in many promising electrochemical biosensor technologies. Compact, high-quality instrumentation is critical to adaptation of these new technologies especially for distributed applications in the agriculture and food industries. To this end, we have developed ABE-Stat, a fully open-source, battery-powered potentiostat project including a wireless Android interface. ABE-Stat is capable of conducting routine electrochemical analyses including cyclic voltammetry (CV), differential pulse voltammetry (DPV), high impedance potentiometric measurements, and can connect directly to the internet through WiFi or indirectly through the Android interface. Importantly it is the first fully open-source potentiostat capable of evaluating electrochemical impedance spectroscopy (EIS) across a wide frequency spectrum (0.1 Hz to 100 kHz) with user selectable amplitude and bias. Current noise was observed to be over an order of magnitude larger than the nominal resolution of the embedded 24-bit analog to digital converter (ADC), but were largely consistent with the actual ADC specifications. In this manuscript we share detailed documentation for ABE-Stat including hardware design and source code, and evaluation of the performance of all avaiable analyses. We also suggest design improvements that could improve the noise performance of ABE-Stat and consistency of EIS measurements across the spectrum.

2,5-dimethoxyaniline was electrochemically polymerized on glassy carbon electrodes, resulting in significant enhancement on the oxidation of glutamic acids. Differential pulse voltammetry of the thus-modified glassy carbon electrodes in a 0.1 mM of D- and L-glutamic acid solution generated two isolated peaks that were separated by more than 400 mV, indicating the feasibility of using this low cost and readily-to-fabricate platform for differentiating glutamic acid chiral molecules. Scanning electron microscopy measurements show that the in-situ synthesized 2,5-dimethoxyaniline polymer has a chain structure consisting of many nanometer size particles. Cyclic voltammetry experiments suggest that the oxidations of D- and L-glutamic acids are both charge-transfer controlled processes. Using cyclic voltammetry method, the anodic peak currents were found to have a linear relationship with the concentration of glutamic acids within the range between 0.5 and 15.0 mM, with a detection limit of 0.11 mM for L-glutamic acid and 0.26 mM for D-glutamic acid. The device-to-device reproducibility is great, confirming the robustness of this modification method.

A novel electrochemical carbon paste sensor containing 10% magnesium doped with zinc oxide nanoparticles was developed and used for electrochemical detection of an anti-inflammatory drug, mefenamic acid. The electrode materials were characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray powder diffraction. Electrochemical and square wave voltammetric techniques were employed to find the lowest possible limit of detection to quantify mefenamic acid. Analytical experiments were performed over the pH range of 3.0–11.2. The pH 7.0 was found to be suitable for the analysis in real samples of human urine as well as a pharmaceutical dosage form. The present work was compared with our early findings based on barium zinc oxide modified glassy carbon electrode to understand the effect of variation of dopant. The results suggested that the dopant significantly affected the electrochemical determination of the analyte and better results were obtained with the modified electrode.

Network polymers have been synthesized by means of catalyst free thiol-yne reaction of multi-functional aromatic ethynyle and thiol compounds, 1,3,5-triethynylbenzenen (TEB), 1,4-diethynylbenzene (DEB), 1,4-benzenedithiol (BDT) and benzenethiol (BT). The network polymers of TEB/DEB-BDT or TEB-BDT/BT were obtained in good yields. The feed ratio of DEB or BT increased the chloroform solution, fragments, of the network polymers. The fragments of the network polymers showed optical properties derived from conjugation units of phenyl-ethynyl-sulfide. The network polymers have been synthesized by oxidation reaction of multi-functional aromatic thiol compounds, 1,3,5-benzene trithiol (BTT) with BDT or 4,4'-biphenyl dithiol (BPDT), accompanied by formation of disulfide bonds. The BTT network was degradable by a reductant, tris(2-caboxyethyl)phosphine hydrochloride.

This work presents an approach to tailor the properties of the graphene oxide- silver nanoparticle (GO-AgNPs) composite using room temperature atmospheric plasma treatment. In particular, the aerosolized deposition of graphene oxide-silver nanoparticle composite (GO-AgNPs), the rapid reduction of GO at room temperature, and AgNPs surface excitation are investigated in this work. The plasma treatment of aerosolized GO leads to the reduced graphene oxide (rGO) formation which is observed from the increase in D to G band ratio from 0.65 for GO to 1.2 for rGO in the Raman spectra. Scanning Electron Microscopy, Transmission Electron Microscopy, and Selected Area Electron Diffraction patterns show that the plasma treatment leads to the morphological changes and the Electrochemical Impedance spectroscopy results show the improvement in the conductivity of the rGO-AgNP composite. To demonstrate the efficacy of the technique, plasma treated GO and silver nanoparticles (AgNPs) composite is used for the electrode surface modification of the commercial screen-printed electrodes for the cortisol detection. The cyclic voltammetry scans to detect cortisol shows that the sensitivity of the surface modified electrodes is increased after plasma treatment. This room temperature atmospheric plasma annealing technique is of specific interest for rapid processing of nanoparticles on flexible surfaces without subjecting them to elevated temperatures.

Polymer nanocomposites are potential materials for three dimensional (3d) printing of functional components. For effective 3d printing, besides ensuring high conductivity of the nanocomposites, their flow characteristics also need careful adjustment. To satisfy the contradictory requirements, multiwalled carbon nanotubes (MWCNT) have emerged as an attractive option. As the dispersion of the MWCNT is believed to strongly influence the properties of the nanocomposites, we compared nanocomposites prepared using melt mixing and solution casting. The MWCNT endow the nanocomposites with appreciable conductivity even at relatively low loadings. At these loadings, the low frequency storage modulus indicates that the MWCNT impart solid-like character to the nanocomposites. While the conductivity percolation threshold of the nanocomposites prepared by melt mixing was lower, at higher loadings the conductivity of the nanocomposites prepared by the two methods were similar. Fitting the electrical conductivity and the linear viscoelastic storage modulus to power-laws, the obtained critical exponents for the two methods were close to each other and to the percolation theory predictions for the conductivity exponent. Our findings suggest that for MWCNT/ABS polymer nanocomposites, simple melt mixing can yield conductivities that are similar to that obtained by solution casting and close to the highest values reported in the literature.

Electrochemical self-assembly of CuSCN/4-(N,N-dimethylamino)-4'-(N'-methyl)stilbazolium (DAS) hybrid thin films has been carried out on systematic variation of bulk concentrations of [Cu(SCN)]⁺, DAS tosylate (DAST) and changing their flux density by angular speed of rotation of the rotating disk electrode. Switching of DAS loading mechanism dependent on the DAST concentration in the bath has been verified and quantified. The switching occurs at the concentration ratio of the precursors DAST/[Cu(SCN)]⁺ = ca. 1/31, molar ratio of the product DAS/CuSCN = ca. 1/48, below which the loading becomes diffusion limited for DAS to be occluded in the CuSCN grains, whereas surface reaction for formation of complex between CuSCN and DAS begins to limit the DAS loading when the relative concentration of DAST exceeds this border, resulting in a phase-separated precipitation of CuSCN and (DAS)(SCN) aggregate in unique nanostructures.

Molecular orientation control with a template material, perylene 3,4,8,9-tetracarboxylic dianhydride (PTCDA), was investigated for various π-conjugated crystalline molecules, namely copper phthalocyanine (CuPc), N,N'-Dimethyl-3,4,9,10-perylenedicarboximide (MePTC), pentacene and dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene (DNTT). The molecular orientation of CuPc and MePTC clearly changed from edge-on to face-on orientation by depositing on PTCDA. The electron mobility of MePTC, which is an n-type organic semiconductor suitable for vertical carrier transport, improved approximately three times owing to face-on molecular orientation. Thin-film X-ray diffraction studies revealed that the molecular packing mode (stacking or herringbone) affects the molecular orientation control. The MePTC film oriented with PTCDA was applied to a vertical-type organic transistor, a metal base organic transistor (MBOT), resulting in higher output current and current gain.

Two stochastic sensors based on the nanographene (nanoGR) paste and on the paste of exfoliated graphene (exfGR) modified with 2, 2-diphenyl-1-picrylhydrazyl (DPPh) were designed and used for the molecular enantiorecognition of D- and L-glucose in urine and whole blood samples. The largest linear concentration range (18.40–1180.00 mg dL⁻¹) for the molecular enantiorecognition and determination of D-glucose in whole blood was obtained using the stochastic sensor based on exfGR/DPPh; this range is able to cover both diabetic and non-diabetic patients. The largest linear concentration range (0.1–2.3 mg dL⁻¹) for the molecular enantiorecognition and assay of L-glucose in whole blood samples was obtained using the stochastic sensor based on nanoGR. For the molecular enantiorecognition of D-glucose in urine samples the largest linear concentration ranges (D-glucose 2.30–2500.00 mg dL⁻¹; L-glucose 1 × 10⁻⁴–10 mg dL⁻¹) were obtained using the stochastic sensor based on nanoGR. The recoveries values (higher than 99.00%), and the low relative standard deviation values (less than 0.10%) proved that the proposed stochastic sensors can be reliable used for the molecular enantiorecognition and assay of D- and L-glucose in biological fluids such as whole blood and urine. Enantioanalysis of glucose will facilitate the clinical research needed to establish the role of the ratio between L- and D-glucose in diabetic and nondiabetic patients.

We present a flexible plastisol-based microfluidic process integrated with conductive nanoparticle composite polymer (C-NCP) electrodes for flexible active microfluidic devices on textile substrates. First, we characterize the stretchability and flexibility of both plastisol films and microfluidic channels. A maximum elongation increase of 37.5% is observed for plastisol films, and a maximum elongation increase of 17.5% is observed for microfluidic channels. We also demonstrate multiple levels of microfluidic channels. Using a new integrated fabrication process, a device that measures the conductivity of fluid between two electrodes is fabricated on a textile and successfully demonstrated and characterized. For this new fabrication process, flexible screen-printable Ag C-NCP, with resistivity of 2.12  × 10⁻⁶ Ω·m, is used for device electrodes. Commercial Ag epoxy, with resistivity of 1  × 10⁻⁶ ∼ 10  × 10⁻⁶ Ω·m, is also used to fabricate a second set of electrodes for comparison. The device is tested with saline solutions at different salt concentrations, and the current through each saline solution is measured at different voltages using both Ag C-NCP electrodes and Ag epoxy electrodes. The current increases linearly for a given voltage as the salt concentration increases, for devices with both Ag C-NCP electrodes and Ag epoxy electrodes.

In order to realize sustainable renewable energy supply, large-scale energy storage system is needed to overcome the problem of intermittency of power generation. Vanadium redox flow battery (VRFB) presents the most viable solution but faces the problem of high material cost. In this study, we have established a cost-effective process to prepare vanadium electrolyte for VRFB from an untouched industrial waste, ammonia slag, by pH control under atmospheric condition (< 95°C). The extracted solution changed color during electrolytic reduction as yellow, blue, dark green and purple, matched with the colors of V⁵⁺, V⁴⁺, V³⁺, and V²⁺, respectively, indicating accurate change of the valences without forming precipitates. Electrolyte prepared from the recycled vanadium showed almost the same charging/discharging performances as the one prepared from commercial V₂O₅ reagent battery tests during the first several cycles, but degraded rapidly after 16 cycles, caused by impurities that deactivate the negative electrode for the reduction of V³⁺ to V²⁺. The miniature VRFB prototype built by employing 3D printing technique showed a much higher performance than the H-cell, indicating the flow cell configuration could help to push up the diffusion limit of vanadium redox by flowing the electrolyte solution through the electrodes, as well as reducing IR loss and water splitting to increase the efficiency.

In this study, we performed a micro/nanocrystallization of charge transfer crystals (CTCs) composed of tetrathiafulvalene (TTF)–tetracyanoquinodimethane (TCNQ) via a charge transfer-induced reprecipitation method. Depending on the order of injected solution, TTF–TCNQ CTCs formed a nanorod or a nanorod-coated rhombic shape. We concluded that the crystallinity of the TCNQ particles in the water dispersion determines the final CTC shape.

Herein we report for the first time a highly sensitive electrochemical platform for the trace level detection of Pb (ӏӏ) using glassy carbon electrode modified with 1-dodecanoyl-3-phenylthiourea (DPT). The performance of the designed sensor was tested by electrochemical impedance spectroscopy, chronocoulometry, cyclic voltammetry and Square Wave Anodic Stripping Voltammetry (SWASV). The DPT was found to play an efficient role in enhancing the sensing response of the electrode for the detection of lead ions in aqueous samples. A number of experimental conditions such as deposition potential, accumulation time, surfactant concentration, pH, number of scans and supporting electrolytes were examined to optimize conditions for getting intense signal of the target analyte. Linear calibration curve was obtained using SWAS voltammetric data obtained under optimized conditions. The limit of detection with a value of 0.695 μg/L suggests that the designed sensor can sense lead ions even below the permissible concentration level (10 μg/L) recommended by the World Health Organization and Environmental Protection Agency of USA. The designed sensor demonstrated sensitivity, selectivity and stability for the targeted analyte. Percentage recoveries from real water samples with standard deviations of less than 2% suggested precision of the proposed method. Moreover, computational findings supported the experimental outcomes.

Slide-ring gel is a highly deformable polymer gel prepared by cross-linking rings on polyrotaxanes, in which ring molecules are threaded onto a linear polymer chain. The remarkable extensibility of SR gels is due to the stress equalization effect caused by the sliding of cross-links on polymer chains. We directly observed the stress equalization effect by magnifying the instinctive micron-scale defect to artificial millimeter-scale crack and then mapping the crack tip stress field based on photoelasticity. By reducing coverage of rings on polymer chains in SR gels, obvious crack blunting and delayed crack growth are observed. Highly elongated non-linear "cohesive zone" with length of 0.6 mm and width less than 0.1 mm occurs ahead of crack tip before crack propagation. Our results show that SR gels with low ring coverage have large cohesive strength to survive large deformation before elastic chains rupture, which is essentially derived from the sliding of the cross-links that adjusts strand length automatically to equalize stress in the network.

The modulation of mold temperature during injection molding is a strategic issue since it allows modulating/calibrating interesting properties of the moldings. In this work, thin heating devices were layered on the cavity surface allowing its fast temperature evolution between injection and cooling channels temperatures. The heating devices were made by a conductive layer between two insulating layers with thicknesses selected in order to realize a heating/cooling cycle as fast as possible. Several tests were performed, injecting polypropylene (iPP), using different heating powers and heating times to analyze the effect of the fast cavity surface temperature evolution on the molding morphology and properties. The heat transfer through the mold was modeled, accounting for the Joule effect in the conductive layer of the heating devices. To validate the proposed modeling of the heat exchange during the process, the simulated temperature evolutions at the polymer–cavity and the heating device–mold interfaces were satisfactorily compared with the experimental ones recorded during the tests conducted adopting different mold temperature evolutions. Furthermore, pressure evolutions during the process recorded in different position along the flow path were satisfactorily compared with the simulated ones to validate the predictions of the thermo–mechanical histories experienced by the polymer.

To investigate a morphological structure of hydrated perfluorosufuonic acids (PFSA) in contact with a platinum surface, we constructed a model of this interfacial system for dissipative particle dynamics (DPD) simulations. The model consists of a bead-spring model of hydrated PFSA molecules and a rigid slab of DPD particles that represents a platinum surface. We applied previously proposed soft potentials for the interactions of DPD particles of hydrated PFSA, while we constructed new ones for the interactions between those of platinum and hydrated PFSA, based on first principles calculations and all-atom classical molecular dynamics simulations. A set of DPD simulations were performed with the constructed simulation model. The calculated results suggest that hydrated PFSA tends to form layers of hydrophilic and hydrophobic components near the platinum surface.

A highly sensitive, selective and stable electrochemical sensor for detection of uric acid (UA) in aqueous solution has been successfully developed by deposition of exfoliated graphitic-like carbon nitride (g-C₃N₄) nanosheets on glassy carbon electrode (GCE). The synthesized g-C₃N₄ was confirmed by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Raman spectroscopies. Field-emission scanning electron microscopy (FE-SEM) and High-resolution transmission electron microscopy (HR-TEM) were used to investigate the crystalline structure of g-C₃N₄. The elemental composition was characterized by energy-dispersive X-ray spectroscopy (EDXS). Compared to bare GCE, exfoliated g-C₃N₄ nanosheets (NS) modified GCE exhibited higher catalytic current for UA electro-oxidation at reduced over potential in 0.1 M phosphate buffered saline solution (PBS), which is essential to discriminate interfering analytes. g-C₃N₄ NS modified GCE showed a linear relationship between the electrochemical signal and the UA concentration from 100 to 1000 μM with fast response by differential pulse voltammetry (DPV). The common interferent molecules such as dopamine, ascorbic acid, folic acid, paracetamol, lactic acid, oxalic acid, cysteine, and ciprofloxacin were tested in 0.1 M PBS for the g-C₃N₄ NS modified GCE. It was found that these molecules did not affect the oxidation current of UA when they co-existed in the same buffer solution. Moreover, the modified sensor probe was tested for UA in urine samples with satisfactory recovery values. The proposed sensor offers high accuracy, sensitivity, simple fabrication and low cost. We suggest that g-C₃N₄ NS based sensor can be useful for UA analysis in medical, environmental, food and industrial applications.

In this study, we attempted to prepare supramolecular networks composed of amylosic inclusion complexes with grafted guest polymers by means of phosphorylase-catalyzed enzymatic polymerization of α-d-glucose 1-phosphate as a monomer from a maltooligosaccharide primer. When the enzymatic polymerization was examined in the presence of poly(γ-glutamic acid-graft-tetrahydrofuran) (PGA-g-PTHF), the reaction mixture totally turned into a hydrogel form. The powder X-ray diffraction measurement of a lyophilized sample of the hydrogel suggested that enzymatically elongated amyloses formed inclusion complexes with the PTHF graft chains among the PGA main-chains according to vine-twining polymerization manner to construct the supramolecular network structure. Therefore, the product formed the hydrogel with inclusion complex cross-linking as the enzymatic polymerization progressed. The vine-twining polymerization is the method for the formation of amylose-polymer inclusion complexes in the phosphorylase-catalyzed enzymatic polymerization field, which has been previously developed by us. On the other hand, the enzymatic polymerization mixture in the presence of poly(γ-glutamic acid-graft-l-lactic acid) (PGA-g-PLLA) did not induce the hydrogel formation upon the same operation. In this system, enzymatically elongated amyloses did not form inclusion complexes with the PLLA graft chains due to their bulkiness, but sorely constructed well-known double helical assemblies, resulting in their aggregation in the reaction mixture.

Room temperature solution processing of highly compact, glass-like thin films of ZnO, SnO₂ and Zn-Sn oxide was achieved for the purpose to use them as thin film encapsulations (TFEs) for organic light emitting diodes (OLEDs), by employing photochemical decomposition of metallorganic precursors under vacuum ultraviolet irradiation in dry N₂. While hydration water in the source chemical strongly promoted granular crystal growth, anhydrous precursors achieved highly flat thin films without pinholes and cracks. The analysis by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy and ellipsometry revealed fast decomposition of organic ligand and polycondensation into metal oxide/hydroxide thin films with high densities within 5 minutes. Transmission electron microscopic observation revealed crystallization in about 5 nm size in case of ZnO, whereas SnO₂ remained totally amorphous. Mixing of the two precursors to yield Zn₂SnO₄ and ZnSnO₃ was able to control the degree of crystallization vs. compactness of the thin film to maximize their ability as TFEs to extend the lifetime of OLEDs for about 4 times for operation under ambient air.

Wearable graphene textile embedded smart headband and its feasibility in electrooculography (EOG) applications is demonstrated by benchmarking against clinical Ag/AgCl wet electrodes; where the recorded biopotentials displayed excellent correlation of 91.3% over durations up to hundred seconds. Automatic eye movement (EM) detection is implemented and performance of the graphene-embedded "all-textile" eye movement sensor and its application as a control element toward human-computer interaction (HCI) and human-machine interfaces (HMI) is experimentally demonstrated by: 1) generating digital clock transitions directly from eye blinks for facilitating switching requirements in HCI/HMI applications, 2) controlling and sequentially lighting up a single LED in a 5 × 5 LED array in four directions to draw a pattern of "8", 3) evaluating the limits of the entire system in an hour-long EOG recording session which includes several activities like checking a phone, watching a video, reading, and performing several EMs including blinks, saccades, and fixations. The excellent success rate ranging from 85% up to 100% for eleven different EM patterns demonstrates the applicability of the proposed algorithm in wearable EOG-based sensing and HCI/HMI applications with graphene textiles. The system-level integration and the holistic design approach presented herein which starts from fundamental materials level up to the architecture and algorithm stage is highlighted and will be instrumental to advance the state-of-the-art in wearable electronic devices.

We study the frequency-dependent dielectric polarizability of flexible polyelectrolytes in electrolyte solution by Dissipative Particle Dynamics (DPD) simulations, focusing on the contribution of the electric double layer (EDL) that surrounds the polyelectrolyte. The simulations are based on a recently proposed mesoscopic model that treats the microions in solution at the level of density clouds and solves the corresponding electrokinetic equations using pseudo-particles. The ion diffusivity and the solvent quality are varied systematically. Both factors are found to significantly influence the dielectric properties of the polyelectrolyte: The diffusion of co- and counterions reduces concentration gradients associated with the polarization of the EDL. As a result, the polarizability is a non-monotonic function of the frequency, and in the low-frequency limit, it decreases with increasing ion diffusivity. The solvent quality influences the degree of chain swelling and thus the shape of the EDL. This affects the polarization of the loosely bound co- and counterions in the outer layers of the EDL and leads to a sub-linear scaling of the polarizability with the polyelectrolyte chain length in bad solvent.

The addition of a compact titanium dioxide (TiO₂) layer between the fluorine-doped tin oxide (FTO) coated glass substrate and the mesoporous TiO₂ layer in the dye-sensitized solar cell (DSC) based on the iodide/triiodide redox couple (I⁻/I₃⁻) is known to improve its current-voltage characteristics. The compact layer decreases the recombination of electrons extracted through the FTO layer with I₃⁻ around the maximum power point. Furthermore, the short-circuit photocurrent was improved, which previously has been attributed to the improved light transmittance and/or better contact between TiO₂ and FTO. Here, we demonstrate that the compact TiO₂ layer has another beneficial effect: it blocks the reaction between charge carriers in the FTO and photogenerated diiodide radical species (I₂^−•). Using photomodulated voltammetry, it is demonstrated that the cathodic photocurrent found at bare FTO electrodes is blocked by the addition of a compact TiO₂ layer, while the anodic photocurrent due to reaction with I₂^−• is maintained.

Full color phosphors based on a host material of mullite (Al₆Si₂O₁₃) doped with rare earth (Ce³⁺, Eu²⁺, Ce³⁺-Tb³⁺, and Eu³⁺) were investigated for the possible application for high power LED lightings. Doping these rare earth ions separately resulted in blue, green and red emissions. The mullite phosphors kept 70% of the luminescence intensity even at 200°C, which was explained by the low thermal lattice vibration associated with the low thermal expansion coefficient. Based on the ionic radii and the bond valence sums, the rare earth ions were considered to occupy the vacant Oc site surrounded by 8 oxygens with a void of 2.14 Å in diameter. Electron density mapping derived from the Rietveld analysis revealed the excess electron density around the Oc site as the possible occupation site for the rare earth ions.

An anisotropic proton conductive polymer film was prepared from poly(decylacrylamide-co-12-acrylamidododecanoic acid). The polymer film was prepared on a solid substrate by spin coating and the structure was analyzed by X-ray diffraction measurement. The initial polymer film exhibited featureless diffraction, which indicates that the film was amorphous. On the other hand, when the film was annealed at 60°C under 98% RH, the film structure was converted from amorphous to highly oriented lamellar structure. The proton conductivities of the film parallel and perpendicular to the substrate surface were studied by impedance measurement. The conductivity at the parallel direction increase whereas that at the perpendicular direction decrease with measurement time. This is because the film formed a lamellar structure in-situ during the proton conductivity measurement. In other words, the anisotropic conduction state can be reached as long as the proton conductivity measurements were carried out.

Despite several research efforts, the detailed mechanism that dominates the thermal conductivity of nanofluids has not been explained. We investigated the effect of the chemical surface design of NPs (hydrophobic–hydrophilic balance of the NPs containing Janus surface) and verified the influence of their self–assembled structures on the thermal conductivity of a nanofluid using molecular simulation. When hydrophobic (HO) NPs are added to a nanofluid, they only form one large cluster because they do not prefer to be in contact with water molecules. Hence, an increment in the thermal conductivity of the nanofluid added with HO NPs was observed. On the contrary, the mean cluster size of Janus NPs was limited because of their limited HO superficial areas (attractive domains). Hence, an increment in the enhancement ratio of thermal conductivity was not observed even when the volume fraction of the NPs (ϕ_NP) was increased. Thus, our results demonstrate that the mean cluster size of NPs is the key factor for thermal conductivity enhancement. In addition, this study reveals that it is possible to control the thermal conductivity of nanofluids (or the mean cluster size of Janus NPs) using Janus NPs with surfaces designed using anisotropic chemical interactions.

The gelation mechanism and network structure of mixed κ-carrageenan (KC) and ι-carrageenan (IC) were investigated using particle tracking. The random motion of fluorescent particles (diameter = 100 nm) was utilized to probe local circumstances of the gelling carrageenan at the sub-micron scale. The mean square displacement (MSD) of particles was used to characterize the changes in the network structure on cooling and storage for 1 day. The individual MSD of particles in the mixture showed a large distribution after 1-day storage, indicating the emergence of microstructural heterogeneity in the gel. This heterogeneity was attributed to the frozen structure on the way to phase-separated network structure. The van Hove correlation plots suggested the presence of two groups of particles with fast and slow mobilities in the mixture. Plotting each MSD vs α with the MSD scaled as t^α and t the lag time suggested a bimodal distribution with fast and slow particles. The presence of two groups of particles with different mobilities suggested that mixtures of KC and IC was frozen on the way to a phase-separated network structures made of KC-rich and IC-rich domains with a size of >100 nm due to the network formation of KC and IC chains.

The authors have proposed a fabrication process of "4D printer" for magnetic soft actuators. In this paper, we applied this 4D printer to bio-mimic field and show some examples using a gel material dispersed with magnetic powder. 4D printer is a recently developed process that can print out not only a 3-dimensional structure but also print deformations of the printed structure at the same time. We employed a UV-curable gel material. The material could be used in the same manner as the conventional 3D-printing process. We applied a magnetic field to set magnetic anisotropy in the curing portion during the building step. This anisotropy is set in each portion of the structure so that the printed structures could deform under an applied magnetic field. Using this technique, we demonstrated 2 kinds of biomimetic examples; one is a worm-type soft actuator and the other is an array of artificial cilia. The first example could crawl in a narrow gap. The second one could reproduce a metachronal wave, which is a phase propagation wave found on natural small organisms. We will also show a computational method to design the deformation of the structure.

This study focused on TiO₂-poly(3-chloro-2-hydroxypropyl methacrylate) (TiO₂-PCHPMA) for rapid removal of cationic dyes from aqueous solutions by adsorption and degradation. TiO₂-PCHPMA adsorbed cationic dyes, basic red 2 (BR2), basic red 5 (BR5), basic blue 17 (BB17), and methylene blue (MB), quantitatively in a wide range of pH from 5 to 10. The adsorption proceeded very rapidly, and reached equilibrium in a few seconds. TiO₂-PCHPMA selectively separated cationic MB from a mixture with anionic methyl orange by the selective adsorption ability. The photocatalytic activity of TiO₂-PCHPMA under UV irradiation was higher than that of bare TiO₂. The excellent removal efficiency of TiO₂-PCHPMA either by adsorption or degradation is advantageous in applications for treatment of industrial effluents by the selective separation by adsorption and degradation under UV irradiation.

The viscosity − or more generally the viscoelasticity − of polymer liquids is a key property for the processing as well as the performance of these materials. Molecular theories and numerical methods can provide these quantities, but they all require certain input parameters that nowadays are typically obtained by experiment. In the long term, it would be desirable to obtain these parameters or the whole viscoelastic response by purely computational methods, enabling a full "in silico" design of new materials and processes. In this perspective, we present several test calculations of the viscosity of n-hexadecane, a short-chain analogue of polyethylene. Our calculations are based on both equilibrium and non-equilibrium molecular dynamics (MD) simulations, which are applied to models based on a united-atom force field, a conventional atomistic force field, and the AIREBO-M reactive force field. We compare both the computational cost of the different strategies and the reliability of the different models and we provide some general guidelines for their application to more complex systems.

Within the research and the development of protective carrier platforms intended for oral drug delivery, polymeric microreservoir devices with sizes around 300 μm have been proposed as a delivery system capable of unidirectional drug release. So far, microreservoir devices have been fabricated with simple shapes by means of high-throughput fabrication methods. In this feasibility study, state-of-the-art micro-stereolithography 3D printing is used for the fabrication of various microreservoir geometries. Scanning electron microscopy characterization and conducted resolution tests demonstrated the capability of the used technology and unveils challenges and opportunities associated with the proposed fabrication process.

There is considerable interest in nanostructured materials with interdigitated electrodes (IDEs) platforms to detect and monitor the level of various ions in numerous applications. Herein, we report the design and fabrication of IDEs based pH sensor by using hydrothermal growth of ZnO nanorods (NRs). A four-step deposition of ZnO seed layer followed by a hydrothermal treatment lead to the heavily ordered ZnO NRs patterns on the screen printed IDEs. The structural, chemical compositional and electrical properties of the NRs were investigated and examined by using field emission scanning electron microscopy (FeSEM), atomic force microscopy (AFM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) technique and Keithley 4200 semiconductor characterization system respectively. The sensor capacitance and pH were found to be inversely proportional at a working frequency of 1 kHz. The sensor displayed sensitivity of 1.06 nF/pH in the range of pH 4−10.

Biodegradable, intelligent, and self-healing hydrogel beads showing peroxidase activity has been prepared by adding hemin to "DNA quadruplex hydrogel" beads prepared by assembling dG₄-PEG-dG₄ triblock copolymers through G quadruplex formation between the dG₄ portion. Efficient binding of hemin to parallel G-quadruplexes in hydrogels was confirmed by observing hyperchromicity of hemin absorbance. The enzymatic activity of resulting hemin peroxidase was visualized both with fluorogenic and chromogenic substrates. These observations serve as the first direct evidence of the presence of G-quadruplexes in DNA quadruplex hydrogels utilizing G-quadruplexes.

This paper starts with a short review of smart materials, which can be 4D printed and whose properties can be modified over time through specific stimuli such as heat, light, temperature, electric and magnetic fields. In the second part of the paper, a new polymer material for 4D printing was presented. The material was a thermally activated shape memory polymer (SPM), capable of memorizing a temporary shape and restoring the original one by means of a thermal stimulus. A self-healing behavior was introduced into the polymer, to enhance its durability and make it suitable for application in the fields of soft robotics and actuators. A polycaprolactone (PCL) was selected to provide a shape memory effect, taking into account its molecular weight and the possibility of chemically modifying it in order to make it photo-curable. Self-healing properties were provided by an ureidopyrimidinone (UPy) methacrylate monomer, capable of forming four hydrogen bonds with a self-complementary unit, favored by temperature. This new material was thus 4D printed by a digital liquid processing (DLP) printer. Both the shape memory effect and the self-healing feature were demonstrated, enabling this new material to be used as a raw material for new generation soft robotic actuators.

One-dimensional (1D) composite nanostructures, or vertically aligned composite nanostructures (VACNs), of polystyrene (PS) and graphene nanoplatelets (GNPs) (1.0-5.0 wt%) were precisely replicated by thermal nanoimprint with an anodic aluminum oxide (AAO) template. In this study, we fabricated VACNs of PS-GNPs (1.0-5.0 wt%) with a diameter of 100 nm and length of 10-70 μm, depending on the imprinting conditions. The obtained PS-GNPs 5.0 wt% VACNs showed enhancement of flat film water contact angle increasing from 87±3° to 132±2°. The nanostructures of PS-GNPs exhibit improved surface mechanical properties when compared with the neat PS. The evaluated surface mechanical properties included friction coefficient, surface durability, surface modulus, and hardness. The glass transition temperature (T_g) of PS-GNPs nanostructures increased about 1 to 4°C as compared with their bulk composites because of the immobilization the polymer chain owing to confinement in the AAO template and also due to the surface interfacial interaction effects between PS and GNPs. Moreover, the maximum thermal conduction of 1D PS-GNPs 5.0 wt% nanostructures were obtained with a value up to 1.8 W/m.K due to the control of filler orientation. The PS-GNPs nanostructures showed a higher thermal stability than that the PS nanostructures.

Electrochemical impedance spectroscopy (EIS) and intensity-modulated photocurrent/voltage spectroscopy (IMPS/IMVS) measurements are carried out to investigate the transport and recombination kinetics in dye-sensitized solar cells (DSSCs) employing three different kinds of ZnO nanoparticles: hexagonal bipyramidal (HBP) with predominantly (102) facets, nanosheets (NS) with predominantly (100) and commercial nanoparticles (MZ) with random facets exposed. The order of recombination resistance MZ > HBP > NS revealed from EIS and IMVS did not coincide with the order NS > MZ > HBP of the open circuit voltage (V_OC) of the DSSCs. Chemical capacitance determined by EIS indicated the most negatively lying conduction band edge for NS, that accounts for the higher V_OC despite lower recombination resistance. On the other hand, transport resistance from EIS and electron transit time from IMPS both indicate faster electron transport for well-crystallized hydrothermally synthesized HBP and NS than for the randomly structured commercial MZ. That of MZ, however, was still sufficiently fast compared to the electron lifetime to ensure a good collection efficiency, leading to almost constant short circuit current density (J_SC) among MZ, NS and HBP.

This work reports a biosensor for monitoring xanthine for potential wound healing assessment. Active substrate of the biosensor has xanthine oxidase (XO) and horseradish peroxidase (HRP) physisorbed on a nanocomposite of multiwalled carbon nanotubes (MWCNT) decorated with gold nanoparticles (AuNP). The presence of HRP provided a two-fold increase in response to xanthine, and a three-fold increase in response to the nanocomposite. With a sensitivity of 155.71 nA μM⁻¹ cm⁻² the biosensor offers a detection limit of 1.3 μM, with linear response between 22 μM and 0.4 mM. Clinical sample analyses showed the feasibility of xanthine detection from biofluids in a lesion site due to diffusion of the analyte into surrounding biofluids. Higher concentrations by three-fold were observed from wound proximity, than away from injury, with an average recovery of 110%. Results show the feasibility of monitoring wound severity through longitudinal measurements of xanthine from injured vicinity.

The skin is at the interface of living organisms and their environment, and has evolved interesting structural properties usually over the course of millions of years, providing clues for the design of manmade biomimetic surfaces with favorable fluid mechanics properties. Here, we describe steps to produce silicone rubber films based on microscopy data from shark skin denticles, from data acquisition and manufacturing to attachment to an airfoil for experimental fluid dynamics in large towing tanks. This method is relatively low-cost, may be generalized to other types of patterned micro-structured surfaces, and the manufacturing process may be reproduced by anyone equipped with a 3D printer.

Atactic poly(2-vinyl pyridine) (P2VP) is widely used in several 3D-Printing applications, in blends or, as one of the blocks, in copolymers. Moreover, several applications have been designed by exploiting the stimuli response to the pH shown by P2VP. In this paper we propose an all atom model of P2VP, based on the well-known OPLS-AA force field, which ensures wide compatibility to model complex mixtures and/or interfaces involving P2VP in composite materials. The proposed all-atom model was checked in the reproduction of structural properties and compared with experimental data. Good reproductions of mass density and X-ray scattering pattern confirm the accuracy of the proposed model.