Superhydrophobic surfaces have been attracting research interest in the areas of self-cleaning, drag reduction and fog condensation. However, many artificial superhydrophobic surfaces may be wetted under fluidic pressure and lose superhydrophobicity. To address this issue, the effect of surface morphologies on hydrophobicity and wetting stability should be investigated thoroughly. In this study, the authors describe a hybrid ZnO nanostructure which can be achieved by hydrothermal method. The hybrid nanostructure is constructed with a ZnO nanorods layer topped with a porous ZnO layer. The specific assembling format of the ZnO layers enhanced the stability of superhydrophobicity.

In this reported study, the authors developed a uric acid biochip that does not require extra driving force. Although liquid flow is performed in a very narrow gap (2 μm), the capillary force is generated in this microfluidic device, which was fabricated from poly(methyl methacrylate) (PMMA) using a micromachining technique. The authors have fabricated a 2 μm pillar array through hot-embossing and thermal bonding from a Si master mould. To increase the capillary force, the authors modified the PMMA surface by ultraviolet irradiation followed by poly-L-lysine coating. Electrodes were integrated into the microfluidic device to permit successful electrochemical measurement of uric acid with good reproducibility. This device also solves the problem of expenditure because of its potential scalability for mass production; although it is driven solely by capillary action, it does not require microfluidic pumps or any other additional power supply. The device is suitable for in situ analysis, diagnosis and house calls.

Graphene as a two-dimensional material is particularly attractive because of its excellent electrical conductivity, mechanical properties, large surface area, low coefficient of thermal expansion and very high aspect ratio. However, the water insoluble property of graphene restricts its application in biomedical fields. Therefore the objective of this reported work is to find an efficient way to synthesise water-soluble and biocompatible graphene for biomedical applications. A stable aqueous graphene oxide (GO) solution was first obtained in the presence of non-ionic Pluronic copolymer. The GO-tripolymer showed good solubility in phosphate buffered saline (PBS) and the same UV absorption peaks as GO. Since a traditional reducing agent such as hydrazine had large toxicity, reduced GO (RGO) obtained by hydrazine reduction has some toxicity. In this work, a non-toxic reducing agent of ascorbic acid, galactose or bovine serum albumin was used as a RGO-tripolymer solution. The RGO-tripolymer exhibited good solubility in PBS. Finally, the cytotoxicity of RGO-tripolymers was investigated. Any RGO-tripolymer showed low cytotoxicity.

Micro–nano patterns created directly over solid surfaces to combat microbial activity help in preventing hospital-acquired infections. This Letter is focused on defining surface topologies by laser patterning over solid surfaces. Studies on designing surface topologies and bacterial culture have been carried out and the feasibility of micro scale features in restricting bacterial growth has been investigated. The effects of the engineered roughness index and contact angle are discussed. Contact angle measurement over patterned surfaces using a novel computer vision-based technique is demonstrated and the effect of contact angle on bacterial adhesion has been presented. The results obtained show that the designed micro scale geometries can effectively reduce the growth of bacteria on the said surfaces.

The use of atomic force microscopy (AFM)-based robots for moving cylindrical particles has become the focus of attention in recent research works. The impossibility of observing the moving process during motion has highlighted the role of computer simulation in the investigation of nanoparticles’ movement. The motion modes (sliding, rolling, spinning) are used to investigate the mode by which a particle moves on a substrate. By using the presented model it is possible to simulate the conditions under which each of these modes are created. To validate the results, it has been observed that by gradual reduction of the nanorod's length, the obtained results are more similar to the results of the spherical case. Furthermore, the presented modes have been evaluated by comparing with the experimental findings, which shows adequate compatibility and acceptable accuracy. In this Letter, first, the movement of particles is modelled and then the effective parameters of the process are simulated. Afterwards, the simulation of dynamic modes is carried out and, finally, verification of the results is presented. By using the presented simulations, it would be possible to predict the mode of movement during the manipulation of nanorods by means of AFM nanorobots.

The demand for more compact devices has led to the growing demand for system-on-chip (SoC) devices. In this reported work a system has been designed that would target a specific protein by using antibodies for the capture and binding. By using the TSMC 0.35 μm bio-microelectro-mechanical systems (BioMEMS) technology, a SoC device that incorporates the sensor and readout circuit into one chip is achieved. The sensor system will be able to detect the quantity of the magnetic beads on the sensor surface. The gold layer from the BioMEMS process has high sensitivity for capturing and fixing the target antibodies on top of the sensor. The system consists of a front-end sensing coil inductor and signal processor. The coil is used as the source of magnetic fields for magnetising the magnetic beads. Using a multiplexer to switch the sensor cells is a way to obtain the signal and infer the amount of the magnetic beads on a specific sensing region. Finally, UV epoxy was used to package the bonding wire of the sensor chip to make sure that biological fluids can directly drop onto the chip without short circuiting the system.

Well dispersive and single-crystal lead titanate (PbTiO₃) whiskers were successfully synthesised by sintering lead acetate and titanium dioxide with improvement of adding potassium chloride as flux at a relatively low temperature. The starting materials were homogenised by different molar ratios and the as-prepared samples were pre-treated before characterising by X-ray diffraction, a scanning electron microscope and a transmission electron microscope. Comparison experiments indicated that the temperature and the amount of flux played an important role in determining the morphology and purity of the products. A liquid–solid growth mechanism is proposed for formation of PbTiO₃ whiskers.

Hexagonal NbSe₂ nanoplates have been successfully prepared via solid-state reaction by a ball-milled mixture of Nb and Se powders. The as-prepared products are characterised by an X-ray diffractometer, scanning electron microscopy and transmission electron microscopy. The results showed that the NbSe₂ nanoplates have a hexagonal structure and the sizes of nanoplates are about 1 μm in diameter and 100–300 nm in thickness. The tribological properties of hexagonal NbSe₂ nanoplates as a lubrication additive in paraffin base oil were investigated by a UMT-2 ball-on-plate friction and wear tester. The wear scars were measured by a VEECO WYKO NT1100 non-contact optical profile testing instrument. The study shows that under determinate conditions, the friction coefficient of the base oil containing NbSe₂ nanoplates is lower than that of pure base oil, and it decreases with the increase of mass percent of NbSe₂ powders when its proportion is lower than 2 wt%.

To measure glucose accurately, a high sensitivity piezoresistive four-set Wheatstone bridge structure microcantilevers glucose biosensor was developed. The microcantilevers with a piezoresistor were fabricated using a series of bulk silicon processes based on a silicon-on-insulator wafer. An improved Wheatstone bridge readout circuit with voltage closed-loop auto-zero and high-gain magnified functions is proposed. The sensing microcantilever gold-coated surface was functionalised by immobilising a self-assembled monolayer of 4-mercaptophenylboronic acid, the reference cantilever was not functionalised. The relationship between a piezoresistive bridgeout caused by the microcantilevers bending and glucose solution concentration was obtained at 5 and 15 mM. Experimental results demonstrated that the output voltage induced by microcantilevers bending is proportional to the glucose concentrations and the sensitivity is up to 0.1 V/mM.

Mesoporous Fe₃O₄/carbon dots (CDs)/silica microspheres with large surface area, good fluorescence and magnetic property have been synthesised with as-prepared Fe₃O₄ nanoparticles, silane-functionalised CDs and tetraethyl orthosilicate as co-precursors and cetyltrimethyl ammonium bromide as the pore-directing agent. Because of their good blue fluorescence, magnetic property and large surface areas, these particles were found to have potential in bimodal cellular imaging, drug delivery, molecular targeting and as building blocks for the assembly of complex nanostructures.

Polydimethylsiloxane (PDMS) microchannel surfaces were modified by air plasma to improve their applicability in microfluidics. The procedure included an increase in air plasma duration from 10 to 30 s. This resulted in an increase of wettability which was demonstrated by the decrease of water contact angles from 105° to 8°. The surface modification-assisted PDMS microchannel easily bonded to a glass surface, and a PDMS/glass microfluidic device was fabricated with a simplified process. Slight pressure applied directly over the PDMS microchannel (approximate dimensions of 2.5 µm deep and 8.8 µm wide) formed nanoslits with dimensions of 830 nm in width and 170 nm in height on the PDMS/glass interface. Nanoslit formation was directly correlated to the metastable collapse of PDMS microchannels on the glass surface after the plasma treatment. The fabricated microfluidic devices were successfully employed for λ-DNA capillary migration without any external driving force.

CdTe nanowires (NWs) are synthesised via a thermal evaporation process, and the structure characterisations reveal that the as-synthesised NWs are single crystalline with a zinc blende structure and a crystal growth direction of [111]. Nano-field-effect transistors are fabricated based on individual CdTe NWs, and the electrical properties demonstrate that the CdTe NWs have p-type conductivity with a mobility (μ _h) of 6.8 × 10^{− 2} cm² V^{− 1} S^{− 1} and carrier concentration (n _h) about 3.6 × 10¹⁹ cm^{− 3}. This significant p-type conductivity is attributed to the intrinsic defects of Cd vacancies in NWs, and then, the high-aspect ratio and nearly perfect single-crystalline quality in one-dimensional NWs are conducive to excellent electron transfer characteristics. The synthesised NWs with significant p-type conductivity will be very attractive candidates for nanoelectronic devices.

Visible photoluminescence (PL) from laser-etched silicon nanostructures has been analysed. A systematic size dependence study of PL from silicon nanostructures has been performed. The PL from these structures is attributed to the quantum confinement effect. Different quantum confinement models have been used for PL and Raman lineshape fitting to calculate the mean size and size distribution of silicon nanostructures and the results are comparatively studied. Calculated values of oscillator strength and radiative lifetime show that PL is due to radiative recombination of confined excitons.

Silver nanoparticles were synthesised on the modified cotton fibres using an in situ method. Acrylic acid was grafted on the surface of cotton using plasma technology as a means to enhance the loading efficiency of nanoparticles. The loading efficiency of silver nanoparticles into the cotton fabric was examined by an atomic absorption spectrometer. The surface of the fibres was characterised by low-voltage scanning electron microscopy and attenuated total reflection-Fourier transform infrared spectrometry. The cotton fabrics loaded with Ag nanoparticles were examined by thermogravimetric analysis. In addition, the antibacterial activity of loaded samples was determined according to the AATCC test method 147-2004. Grafting of acrylic acid on cotton fibre leads to increase in the loading efficiency of silver nanoparticles and this sample showed the highest antibacterial activity.

In this Letter, the cooling performance of microchannel heat sinks, as well as a comparison of the heat the transfer efficiency of two nanofluids: Al₂O₃–water and multiwall carbon nanotube (MWCNT)–water and pure water, is investigated. At first, the same pumping power inlet boundary condition, which is a standard comparison of the performance of different fluids, is applied for a single rectangular duct, and the results are stored for the modelling of the heat sink. Following this stage, a heat sink made up of aluminium with water as working fluid is modelled. After validation of the results and optimisation of the grid, the efficiency of the three fluids is compared. It is seen that by using MWCNT–water nanofluid instead of water in a typical heat sink, the mean reduction in thermal resistance for MWCNT–water and Al₂O₃–water, in comparison with using water, respectively, are 18 and 1%. This shows the great advantages of using MWCNTs in heat sinks in comparison with Al₂O₃.