As a result of this reported research, a simulation model to analyse the behaviour of carbon nanotube field effect transistors (CNTFETs) under non-ballistic conditions is explained and the effect of gate dielectric on the performance of CNTFETs has been explored in detail. For the first time, a thorough study of the combined non-ballistic effect on the performance of CNTFETs has been conducted and the output of the device has been analysed. It has been observed that a gate material with a high dielectric constant leads to higher on-state current and higher on and off state current ratio. In addition, the transconductance, total capacitance, charging energy, subthreshold swing (S), drain-induced barrier lowering (DIBL) and gain with respect to the dielectric constant have been observed and analysed. Transconductance and total capacitance increases by a significant amount, while charging energy and S decrease as the dielectric value increases. The DIBL and gain vary slightly as a higher value dielectric material is used as a gate. Furthermore, the results of this study have been plotted against previously reported ballistic outputs to provide a better perception of the deviation from ideal behaviour. At the same time, the outcomes of this analysis have been compared against some reported experimental values.

An investigation has been conducted into the electron transport properties in carbon nanotube (CNT)–graphene contacts with a fully non-equilibrium Green's functions method combined with the density functional theory. Four different models are considered, where the contact geometries are varied. Their similar electron transmission characteristics are demonstrated with little dependence on the contact conditions at high energy and considerable dependence at low energy. The vacuum gap hinders the electron transport, resulting in an additional contact barrier. The electron transmission is mainly performed between the boundary carbon atoms of the CNT and the nearest graphene atoms, and the imperfection of the edge carbon atoms in a hexagonal lattice destroys the ballistic transport in graphene and the CNT at the contact. The current–voltage characteristics are presented as well. This reported work gives an insight into the electronic transport properties of the contacts and suggests that graphene is a suitable electrode material for applications in full-CNT devices.

A unique approach for the fabrication of long-aspect ratio microtubes is presented for an antimatter trap. Conventionally, non-neutral antimatter is stored using a Penning-Malmberg trap, a single tube with aspect ratios being of the order of less than 10:1. Parallel microtubes with aspect ratios of 1000:1 have the potential to store many orders of magnitude more. The silicon industry has paved the way to microelectromechanical systems technologies which have been utilised in this research. Standard processes such as photolithography, deep reactive ion etching, sputtering and thermo-compression bonding were all used; however, unique methods of these processes were developed to overcome many engineering challenges and realise successful trapping.

In this reported work, the extinction coefficient of water-based nanofluids containing multi-walled carbon nanotubes (MWNCTs) has been experimentally measured. The MWCNTs were dispersed in deionised water with a surfactant, hexadecyltrimethyl-ammonium bromide, and they were homogenised by a bath-type ultrasonicator and a mechanical stirrer. The characteristics of MWCNTs suspended in the nanofluids were examined by transmission electron microscopy and scanning electron microscopy images and their hydrodynamic particle size was measured by a particle size analyser. The extinction coefficient of nanofluids was measured by an in-house developed apparatus at a single wavelength (632.8 nm) based on the Lambert-Beer principle. With the experimentally obtained extinction coefficient, the efficiency of a flat-plate type direct-absorption solar collector (DASC) was theoretically estimated. For this purpose, a modified analytical solution of the DASC efficiency is presented by assuming that the extinction coefficient is not a function of the wavelength. Finally, the efficiency of DASC is demonstrated according to the nanotube volume fractions. The results show that the DASC concept can further improve the efficiency of the conventional flat-plate type solar collectors.

A dual-band microbolometer coupled with an H-shaped fractal antenna, which can detect both infrared (IR) and THz waves simultaneously is proposed. Firstly, the H-shaped fractal antenna for 125 and 500 μm dual-bands is proposed by using the dipole antenna formula and finite element method (FEM) simulation. On the basis of simulation results, the H-shaped fractal antenna for the microbolometer is fabricated and the electromagnetic wave absorption characteristics of it are measured. Transmission measurement successfully confirmed the absorption peaks near the aimed for two wavelengths in the IR and THz regions, respectively. It showed that the proposed microbolometer coupled with the H-shaped fractal antenna is considered as a useful tool for widely separated multi-band detection. Moreover, for the microbolometer design, the influence of bias line resistivity on microbolometer characteristics with two different bias line materials by the FEM simulation is studied. It is observed that the electromagnetic wave absorption characteristics of the microbolometer are affected by the resistivity of the bias line material, especially when the parallel polarised incident wave to the bias line formation direction is irradiated.

A highly applicable theoretical model and a simple, inexpensive mould-based method is introduced to design and fabricate the pyramid-shaped SU-8 microneedle. The main purpose is to be able to extract blood at point-of-care sites from up to 80% of typical nurse-home patients with a disorder of blood circulation in fingers and toes (Raynaud's phenomenon). Geometry optimisation was conducted based on the study of fracture force, which can be accurately predicted by the proposed theoretical model. The accuracy of the proposed theoretical model was confirmed by the finite element study and practical measurement. For practical verification, measurement of fracture force was conducted on fabricated SU-8 microneedles, including a 1470 µm-tall pyramid-shaped microneedle and a 1515 µm-tall traditional-shaped microneedle. The measurement results confirmed the improved strength of the proposed pyramid-shaped microneedle, especially of the pyramidal tips, which can exhibit significantly higher applied force with 2.82 N compared with the 0.51 N bevel tip. Practical tests of skin penetrability on human fingers showed that the microneedles fabricated with the proposed geometry may be sharp and strong enough to safely puncture human skin and long enough to reach the blood vessels.

A micromachined cantilever-based flow sensor is designed based on differential pressure. Numerical analysis and analogue simulation are used to investigate the FSI (fluid–structure interaction) characteristics of the differential pressure flow sensor. The FSI model is created using the hydromechanics and elastic mechanics, and a systematic theory is established to complete the numerical analysis. Then the working mechanism of the flow sensor is analysed depending on the FSI results. The analogue simulation is undertaken by the commercial software FLUENT and ANSYS. The result of the numerical analysis is similar to that of the analogue simulation. Considering the results of the numerical analysis and the analogue simulation, the shape and size of the flow sensor are optimised. Moreover, the optimised flow sensor is fabricated and calibrated. The calibration results show that the cantilever-based differential pressure flow sensor achieves ideal static characteristics and works well in practical applications.

A fabrication process of silicon hierarchical nanopillar arrays (NPAs) based on the self-assembled colloid particle monolayer is presented. Using colloid particles assembled by the evaporation-induced method as masks, well-ordered silicon NPAs were fabricated by assessing the deep reactive ion etching process. After the optimisation of the cycles of etching and passivation steps, double-layer hierarchical NPAs were achieved simultaneously. Systematic analysis and experiments were conducted to investigate the transition from well-ordered silicon NPAs to silicon hierarchical NPAs. An explanation of this transition is provided based on the collapsing phenomenon discovered in the experiments.

To investigate the mechanical strength of the anchor–microbeam combined structure, two series of devices (bonding quality testing devices and torsional strength testing devices) are designed and fabricated by the silicon-on-glass process. A novel array-shaped anchor scheme is presented, which has been compared with the conventional single anchor. The experimental results have shown that the bonding quality of the anchor degenerated severely when the bonding area became very small (<400 μm²). The testing results of bonding quality testing devices demonstrated that the presented array-shaped anchor design helped to improve the anodic bonding yield. According to the bending fracture test of the torsional strength testing devices, the array-shaped anchor design had an almost equal torsional strength compared with the single anchor with the same occupied area. Moreover, the torsional strength of the array-shaped anchor was even greater when the bonding area was the same. In the fracture test, the fracture would happen in the anchor since the structure size was small. When the structure was larger, the fracture happened in the cantilever beam, rather than the anchor.

A microresonant accelerometer which consists of silicon substrate and a quartz double-ended tuning fork (DETF) is described. A temperature isolator structure on the silicon substrate is designed to decrease the influence of thermal stress on the DETF's tines. Two stiff ends of the quartz DETF are mounted on the proof mass and temperature isolator, respectively. When acceleration is applied, the proof mass will move, inducing the variation of axial stress on the DETF's tines. The resonance frequency of the DETF's tines will change corresponding to the stress, so acceleration can be measured. The DETF is excited by the inherent piezoelectric property of quartz based on the anti-phase in-plane bending model. Both the silicon substrate and the DETF are fabricated by micromachining. The sensor is analysed by finite-element simulation. According to the simulation, the temperature isolator decreases thermal stress by 30.2%. Experimental results show that the resonance frequency of the sensor is 35.2563 kHz and the sensitivity is 8.55 Hz/g, which is in good agreement with analytical calculation.

Conventional metal microparts were fabricated by a series of complex photolithography, sputtering, sacrificial layer and release processes. This reported work demonstrates the integrated process of metal microparts using 1064 nm Nd:YVO₄ laser direct-write patterning of indium tin oxide (ITO) thin films on glass, followed by the electrochemical deposition of copper (Cu) on the pattern. The ITO thin film could be removed without any damage to the glass structure through the diffractive multiple Nd:YVO₄ beam. A high overlapping area of the laser spot was used to pattern the electrode layer on the film surface for obtaining a 50 µm ablated edge profile with a linear boundary after laser patterning. A high quality of surface could be achieved at a proper parameter control without numerous processing steps. Compared with conventional photolithography and etching technologies, direct-write micropatterns of ITO using the Nd:YVO₄ laser is a maskless, dry and low-cost process. Accordingly, the micrometal parts can be obtained using the electrochemical deposition and release process of laser-patterned ITO films because of the adhesion property of Cu on ITO.

A new enabling technology for low-cost high throughput parallel scanning probe nanolithography is presented. Monolithic integration of microelectromechanical systems (MEMS) actuators with two-dimensional probe arrays as well as preliminary results in the simultaneous generation of multiple submicron patterns using such structures is reported. Two-degree-of-freedom electrothermal MEMS positioning structures integrated with nanoscale probe-tips are used to perform parallel scanning probe nanolithography circumventing the main deficiency of tip-based nanolithography, that is, low throughput. Simultaneous generation of multiple patterns scratched into 800 nm thick photoresist and 200 nm thick gold layers has been successfully demonstrated. Scratch marks as narrow and as long as ∼50 and 27 µm, respectively, have been generated in the X and Y directions using two different microactuator structures carrying 10 and 64 nanotips.

The fabrication and use of silicon nanowire (SiNW) array-patterned microcantilever sensors for enhancing aerosol mass detection are described. Surface modification of the cantilever is performed selectively by combining the processes of nanoimprint lithography, photolithography and inductively coupled plasma cryogenic reactive ion etching. Cylindrical wire structures of 300 nm diameter with aspect ratios of 3–7 can be realised for the current SiNWs, which can be altered depending on the nanoimprint stamp size and etching recipe. Owing to the rise in the collection surface area of the sensor provided by vertical SiNWs, an increase of aerosol sampling efficiency can be obtained during cigarette smoke exposure, which is a factor of 1.5 higher than that of a corresponding plain cantilever. This proposed structure is intended to be used as a sensor module of a personal aerosol mass detector.

Presented is the configuration design for piezoresistive absolute micropressure sensors. A figure of merit called the performance factor (PF) is defined as a quantitative index to describe the comprehensive performances of a sensor including sensitivity, resonant frequency and acceleration interference. Two configurations are proposed through introducing islands and sensitive beams into the typical flat diaphragm. The stress distributions of sensitive elements are analysed by a finite element method. Multivariate fittings based on ANSYS simulation results are performed to establish the equations on surface stresses and deflections of the two sensors. Optimisation by MATLAB is carried out to determine the dimensions of the configurations. Convex corner undercutting is analysed to estimate the final dimensions of the islands. Each PF of the two configurations with the determined dimensions has been calculated and compared. Silicon bulk micromachining is utilised to fabricate the prototypes of the sensors. The outputs of the sensors under both static and dynamic conditions are tested. Experimental results reveal that the configuration with quad islands presents the highest PF of 210.947 Hz^1/4. The favourable overall performances make the sensor more suitable for altimetry.

Polylactic acid (PLA) was blended with polyethylene glycol (PEG) and spun via a melt-electrospinning system. The effect of PEG content on the PLA melt and the thermal behaviour of the blend was studied using dynamic rheometry and differential scanning calorimetry, respectively. By fitting a rheological model, parameters such as zero-shear viscosity and the relaxation time of polymer chains were obtained. A substantial reduction of zero-shear viscosity and relaxation time by increasing the PEG content from 0 to 30 wt% was observed. Crystallisation peaks shifted to lower temperatures and the crystallinity level increased in PLA/PEG blends against PEG concentration. The results revealed enhanced polymer chain mobility because of the plasticising effect of PEG. Continuous microfibres were obtained by electrospinning of PLA/PEG blends. While neat PLA was not spinnable at the spinning temperature of 200°C, PLA/PEG blends were easily spun and the lowest fibre diameters of 3–6 μm were achieved with 30% PEG loading, at an applied voltage of 70 kV.

Poly(o-aminophenol) (POAP)/multi-walled carbon nanotube (MWCNT) nanocomposite and POAP in the absence of the MWCNT were fabricated by consecutive cyclic voltammetry (CV) on a graphite (G) electrode. The dispersion of nickel (II) ions was accomplished and incorporated into the polymeric electrodes (G/POAP and G/POAP-MWCNT) by immersing them into a 0.1 M nickel (II) solution. Following preparation of G/POAP/Ni and G/POAP-MWCNT/Ni, the electrochemical behaviour was examined using CV. Scanning electron microscopy was used for characterisation of the nanocomposite. The prepared electrodes showed enhanced electrocatalytic activity for the oxidation of acetaminophen and facilitated the detection of acetaminophen in a 0.1 M NaOH solution. Compared with the G/POAP/Ni electrode, the G/POAP-MWCNT/Ni electrode had a significant current response of acetaminophen oxidation because of the synergistic effects of POAP and the MWCNT. By CV, the calibration plot was linear in the range of 1–13 mM with standard deviation between 0.3 and 6.54% for acetaminophen. The G/POAP-MWCNT/Ni was successfully applied for acetaminophen determination in tablets and the results showed sufficient precision and achieved a mean recovery of 96.8% (R.S.D. = 4.9%).

Molecular dynamics simulations and micromechanics model analysis are performed to investigate the mechanical behaviours and interfacial effects of interpenetrating phase composites in the nanoscale. It is observed that the overall Young's modulus and ultimate strength of the nanocomposites vary nonlinearly with the cohesive energy of the interface. The cohesive properties affect the stiffness of the interface zone, and in turn, influence the effective Young's modulus of composites. The competition between interfacial failure and weak phase damage results in an optimal cohesive parameter of the interface, at which the composite possesses the maximal ultimate strength. The obtained results provide useful guidelines for the design and optimisation of advanced nanocomposites with superior mechanical properties.

A series of novel colourful BiOI photocatalysts have been synthesised by a simple oil bath method at 160°C. Several characterisation tools including X-ray diffraction, a scanning electron microscope, energy-dispersive X-ray spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy were used to study the phase structure, morphologies, bandgap and catalytic performance of the prepared samples. The results show that BiOI exhibited higher photocatalytic efficiency under visible light (λ > 420 nm) in the degradation of methyl orange. This result could be because of the narrow bandgap, for which E _g is about 1.4–2.25 eV, and a number of active positions for catalysts. h⁺ acts as the main active species during methyl orange degradation.

A novel manufacturing method of fabricating nanochannels with complex three-dimensional (3D) structures based on a modified atomic force microscopy (AFM) nanoscratching method is presented. By changing the moving trajectories of the AFM tip, arbitrary geometric patterns were obtained. Nanochannels consisting of the superposition of geometric figures could be fabricated through extensively controlling the scanning velocity of the AFM tip and combining the movement of the AFM tip with the high-precision stage. Machining experiments were performed to demonstrate the capability, validity and flexibility of the proposed approach. Finally, nanochannels with complex 3D structures were presented in an automated, flexible but cost-effective way.

Inspired by the anisotropy of the rice leaf surface, high-speed wire electrical discharge machining (HS-WEDM) technology was used to build submillimetre-scale structures on the 304 stainless steel surfaces, and fluorination treatment was applied on the resulting surfaces. The wettability and microstructure of the resulting surfaces were investigated by a large depth 3D scanner, scanning electron microscopy and by the contact angle measuring instrument. The durability of the fabricated surface was evaluated by wear tests. Results show that the V-shaped groove arrays with a hierarchical structure on the processed surfaces are built by HS-WEDM. After the fluorination treatment, the as-machined surfaces show good one-direction superhydrophobicity and the obvious two-direction (the parallel and perpendicular groove directions) anisotropic wettability. The effect of the size of the V-shaped groove on the two-direction anisotropy is discussed. The wear tests show that the one-direction superhydrophobicity and the two-direction anisotropic sliding properties of the stainless steel surfaces are still exhibited after the tests. Fabricating rough surfaces by HS-WEDM is efficient and does not require complex process operation and large area three-dimensional features. This method can realise industrial production.

The silica (SiO₂) sol and hybrid zirconia (ZrO₂)/SiO₂ sol were used to coat cotton fabrics using the pad-dry-cure method to improve their physical and functional properties. The physical properties of coated and uncoated fabrics, such as tensile strength, tear strength, crease recovery angle, air permeability and whiteness index, were tested as per the standard test methods. The wash durability of the coating on the fabric was also analysed after five and 10 wash cycles. The observed results show that the ZrO₂/SiO₂-coated fabric has better physical properties than SiO₂-coated and uncoated fabrics. In addition, an antibacterial activity test confirms that the SiO₂-coated fabric possesses higher antibacterial properties against Escherichia coli and Staphylococcus aureus than the ZrO₂/SiO₂-coated fabrics.

An easy approach for the fabrication of titanium dioxide hollow spheres is proposed. Nanostructures were obtained by the conventional hard template method with silica-protected calcination. The samples were characterised by differential thermal analysis and thermogravimetry, Brunauer-Emmett-Teller nitrogen adsorption isotherms, X-ray diffraction, scanning and transmission electron microscopy (SEM and TEM). Raman spectroscopy and optical properties of the prepared materials were studied as well. X-ray analysis has shown that the silica protection layer allows direct phase transformation from amorphous titania to crystalline anatase regardless of the temperature. The crystallite size is more than 5 nm. The diameter of the obtained hollow nanostructures is within the range 115–420 nm. The thickness of the walls varies from 12 to 38 nm depending on annealing conditions. TEM and SEM images confirm their spherical shape.

Silver (Ag) nanosheets were synthesised through a facile self-seeding strategy with binary reduction in the poly(vinylpyrrolidone) (PVP)–sodium dodecyl sulphate (SDS) aggregation microreactor, in which the size and morphology of Ag nanoparticles were able to be regulated by concentration or pH dependence. In this approach, PVP and SDS built the microreactor together and served as a synthesis template; a trace of sodium borohydride (NaBH₄) was employed to rapidly trigger the competitive formation of small Ag seeds, while PVP was responsible for the subsequent reduction and slow crystal growth. The size and morphology of the nanosheets could be gently regulated with the concentrations of PVP or SDS and the pH of the reaction solution; while the dramatic variance of size and morphology was primarily induced by NaBH₄ concentration. Free PVP monomers with lower concentration induced irregular particles, while the lower concentration of NaBH₄ led to the formation of small and regular nanosheets. Both particle size and morphology could be regulated with SDS concentration dependence if the SDS concentration was higher than the critical aggregation concentration. Higher SDS concentrations favoured smaller particle sizes and nanosheet formation. Two-dimensional planar Ag nanostructures were generated at pH 9–10, where [Ag(NH₃)₂]⁺ existed at a stable complex ionisation state.

Nanocadmium sulphide (CdS) has been prepared by the one-pot solid-state method from cadmium chloride (CdCl₂) and sodium sulphide (Na₂S) without any capping agent. The grinding period plays a major role in transforming CdS from the cubic (zinc blende) to the hexagonal (wurtzite) phase, hitherto unreported at the lowest temperature of 200°C by the solid-state approach. The compounds are characterised by powder X-ray diffraction, UV–visible absorption spectroscopy, scanning electron microscopy and high resolution transmission electron microscopy techniques. On the basis of the results, it has been observed that with only grinding and without subsequent heat treatment, the compounds named with their grinding period as subscript have either zinc blende – CdS_{(30 min)} or mixed zinc blende/wurtzite – CdS_{(2,4, 6 and 8 h)} structures. However, when subjected to heat treatment at 200°C, there is a complete phase transformation to the wurtzite structure achieved only with the CdS_{(8 h)} compound, while the rest of the compounds show similar phases as the compounds prepared without annealing. The photocatalytic efficiency of CdS compounds on methyl orange follows the order, CdS_(cubic) > CdS_{(mixed phase → cubic + hexagonal)} > CdS_(hexagonal), with cubic phase CdS showing greater efficiency than mixed and hexagonal phases.

In this reported work, Mn₃O₄ octahedron submicrostructures (Mn₃O₄ OSMs) were obtained through a facile solvothermal method in mixed solvent. The authors have modified a glassy carbon electrode (GCE) with Mn₃O₄ OSMs and Nafion to obtain a sensing platform (Mn₃O₄ OSMs/Nafion/GCE) for the non-enzymatic detection of H₂O₂. The resulting Mn₃O₄ OSMs/Nafion/GCE exhibited good electrochemical catalytic activity towards the reduction of H₂O₂ in a phosphate buffered solution (0.1 M, pH = 7.0). The linear detection range was estimated to be in the range from 5 µM to 17 mM (R = 0.9998), and the detection limit was estimated to be 1.5 µM at S/N = 3. Real sample analyses show that the sensor developed in this work could be efficiently used for the determination of H₂O₂.

Demand has increased for the double-sided moulding of microfluidic devices for a series of biochemical analyses. Accurate alignment of mould inserts is a critical aspect to transfer doubled-sided patterns on the top and bottom surfaces of a moulded part. A method of mould alignment was studied for double-sided hot embossing of polymer microfluidic devices. An alignment method was designed using kinematic constraints, and a set of three locating pins. To validate the alignment method, two brass mould inserts with fluidic reservoirs were used for the double-sided moulding of prototype microfluidic devices. The kinematic constraints were used to align the mould inserts with each other on the hot embossing machine. The misalignment of double-sided features on the moulded parts was measured using a measuring microscope. The X- and Y-magnitudes of the mismatches ranged from −28 to 118 µm along the X-axis of the moulded parts. The X- and Y-magnitudes of the mismatches along the Y-axis of the moulded parts varied from −38 to 141 µm. The results of the experiments showed that the mould alignment using kinematic constraints is applicable to the fabrication of double-sided patterns for microfluidic devices.

Monodisperse α-Fe₂O₃ nanocubes with a mean size of 85 nm have been prepared by heating an aqueous solution of iron (III) nitrate in the presence of a certain amount of alkali without any additional organic reagents or templates in a hydrothermal route. The structure and morphology of the products were characterised by X-ray diffraction, transmission electron microscopy and field-emission scanning electron microscopy. The results have shown that the crystal morphology continually changes at higher temperatures and α-FeOOH was generated as the intermediate during the hydrothermal dehydration reaction. In addition, the optimum temperature and reaction time of the hydrothermal synthesis of these α-Fe₂O₃ nanocubes were 200°C and 5 h, respectively.

Silver nanoparticles were synthesised successfully using poly(2-acrylamido-2-methylpropane sulphonic acid) (PAMPS) as a surfactant. Silver nanoparticles prepared through this approach possess high purity and narrow size distribution. The size distribution result shows that the diameters ranging from 78.82 to 105.709 nm can account for 76.41% of nanoparticles. UV–vis spectra were used to record the formation of silver nanoparticles in detail. It is found that PAMPS can play an important role in the formation and the colloidal stabilisation of silver nanoparticles because of the high affinity of sulphonic and amide with silver ions. The formation is summarised in detail. In addition, a potential application in nanocomposites of this method is explored. The Ag/polyaniline (PANI) nanocomposite prepared using this method shows higher electrical conductivity than that prepared using other methods. This method is novel, convenient, efficient and environmental-friendly, especially suiting those wastewaters treatment facilities containing silver ions. At the same time, it is also promising to prepare Ag/PANI or other metals/polymer composites via in-situ polymerisation.

It is demonstrated that it is possible to switch the magnetisation of nanomagnets by employing the exchange interaction between magnets. This can implement on-chip clocking for nanomagnetic logic circuits by using a current-carrying copper wire circularly wrapped by ferromagnetic cladding. This scheme is potentially more energy efficient than yoked cladding clocking using an external magnetic field for magnetisation switching. Maxwell simulation shows that current flowing through copper wire can be reduced by about one hundred times compared with yoked clocking, which means power consumption could be lowered by 10⁴ times. Micromagnetic simulation shows that the nanomagnetic chain aligned on the proposed clocking can achieve a correct functional state.