Piezoelectric micromachined ultrasonic transducer (pMUT) is gaining increasing research interest. It overcomes the inherent shortcomings of conventional bulk ultrasonic transducers such as acoustic impedance mismatching and poor sensitivity. In addition, pMUT does not require the extremely large input voltage as capacitive micromachined ultrasonic transducer. Therefore the pMUT is potential to be integrated into portable electronics. A pMUT array operated in air using the lead zirconate titanate (PZT) thin film polled by high voltage pulses is realised and fully investigated. The high voltage pulses are found to be more effective for PZT poling, where the piezoelectric constant d ₃₁ is elevated to 105 pm/V. Benefited from such high performance PZT thin film and optimised structure, the fabricated pMUT (500 × 300 µm) achieves a displacement sensitivity of 807 nm/V at its resonant frequency (482 kHz) without DC offset. Compared with previously reported PZT pMUTs, the sensitivity is superior to them even with a smaller membrane. The in-air transmitting performance is also evaluated. A single pMUT element is able to generate 63.7 dB sound pressure level at 10 mm in air with only 2 V input. The proposed high performance pMUT shows its promise for practical applications in portable electronics.

A high-sensitivity tri-axis force sensor designed to measure the traction force of a single cell is reported. The developed sensor consists of a micropillar that is supported by a cross-shaped Si structure and a double-layer photoresist cap. The piezoresistors formed on the Si structure allow for the simultaneous measurement of the normal and shear forces acting on the micropillar. Moreover, the cap prevents the cells from contacting the Si structure, which is not desirable when measuring the force acting on the micropillar. The effect of the culture medium on the impedance of the sensor and the noise level of the measurement circuit was evaluated. The temperature effect was compensated using a piezoresistor that does not possess a through-hole underneath. For measurement, inside a culture medium, the resolution of the sensor obtained from the standard deviations of the measured signals was less than 2 nN. Finally, it was demonstrated that the sensor is capable of measuring the traction force in three dimensions generated by an osteosarcoma cell when it detaches from the micropillar under trypsin treatment.

The manufacturing process of through-glass-via (TGV) structure and direct implications on the design of quartz-based interposer applications for three-dimensional integrated circuit packaging technology is presented. First detailed substrate thickness formed by dry etching with various associated structures based on the use of thin quartz as a substrate material was analysed. Then, the holes etched in glass wafers by photolithography and inductively coupled plasma-reactive ion etching techniques was evaluated. The fabricated TGV morphology showed an excellent characterisation between substrate thickness, via diameter, and via shape for a vertical interposer. Finally, TGV structure with a diameter of 50 µm × 150 µm thin quartz wafer exhibit high usability for thin wafer processing with the optimised fabrication parameters was obtained.

Transparent conductive electrodes (TCEs) possessing a combination of high optical transmission and good electrical conductivity find applications in numerous optoelectronic devices. A low cost fabrication of a fine metal-mesh structure on rigid (glass) and flexible (polyethylene terephthalate – PET) substrates as a promising and feasible approach for fulfilling large size TCE requirements is proposed. A roll-to-sheet ultraviolet imprinting protocol to transfer microtrench structures using a flexible Polydimethylsiloxane stamp is utilised. The conductive silver ink is filled into the microtrench structures by controlling the processing parameters which include pressure, scraping angle and speed. The metal-mesh based glass and PET substrates show a transmission of about 90%, while the electrical resistance is as low as 6 Ω/□. Thus, this method can be utilised as an economically viable alternative to doped indium oxide in TCE applications.

Redox flow battery has been paid attention since it has been considered as a solution for large-scale energy storage. Among redox flow batteries, this work focuses on zinc (Zn)/bromine (Br) redox flow battery. The cell of Zn/Br redox flow battery as an energy source for a sensor node of wireless sensor network systems was miniaturised. Here, the fabrication and the experimental results for performance characteristics of the miniaturised Zn/Br redox flow battery cell are reported. Moreover, the electrode materials influence on its characteristics utilising four kinds of carbon materials such as activated carbon, hard charcoal, carbon nanotubes (CNTs), and activated carbon and CNTs composite was investigated. To investigate performance characteristics, charge-discharge tests, impedance measurement, specific surface area measurement, and charge and discharge cycling life test were performed. Moreover, the morphology of electrode materials was observed. As a result, it revealed that the activated carbon electrode showed the best coulombic efficiency of 88.6% and the largest specific surface area. Moreover, it was confirmed that the activated carbon and CNTs composite electrode material has the lowest inherent internal resistance and interfacial resistance among the investigated electrode materials. In the cycling life test, the CNTs electrode showed stable capacity retention during ten cycles.

Noroviruses (NoVs) are a major cause of acute gastroenteritis worldwide and spread through person-to-person transmission and contaminated food or water. A miniaturised microelectromechanical systems (MEMS)-based electrochemical aptasensor, a biosensor using aptamer as the recognition element for simple, sensitive and rapid detection of NoV has been developed. The novelty of this work is integration of MEMS technology with aptamer to develop a miniaturised and portable electrochemical sensor for environmental pathogen monitoring. An MEMS electrochemical aptasensor device was prepared by immobilising a thiolated DNA aptamer on an on-chip gold (Au) working electrode through the affinity between thiol and Au, and formation of a DNA aptamer monolayer was confirmed by means of cyclic voltammetry as well as visual observation of a fluorescent-labelled aptamer. The MEMS electrochemical aptasensor exhibited rapid and clear square wave voltammetry response against different titres of murine norovirus, an experimental model of human NoV. The possibility of developing a handheld aptasensor platform using a portable electrochemical measurement device is also demonstrated. This research forms initial basis for the development of an electrochemical MEMS-aptasensor platform and its application for virus detection.

An original highly compression-tolerant folded carbon nanotube (CNT)/paper electrode, which could be assembled into compressible solid-state supercapacitor with polyvinyl alcohol/phosphoric acid gel electrolyte, is designed. It is worth mentioning that both the compression-tolerant ability of the folded structure and the strain ability of the CNT electrode are conducive to achieving the compressible supercapacitor. Such device could withstand pressure and shape-changing, which has great potential to be used in various environments. This compressible solid-state supercapacitor also owns the maximum specific capacitance of 11.07 mF/cm², and capacitance retention retains more than 90% after 100 cycling times. Furthermore, the stability performance of the device is also discussed which is almost steady under 50% strain state. When two devices are connected in serial and fully charged, this power unit could light up a red light emitting diode continuously even under the compression state. Therefore, this device performs as a promising candidate to be compatible with other compression-tolerant electronics and enlightens a broad field of compressible energy storage and self-powered systems.

The design, fabrication and evaluation of single and mechanically coupled capacitive silicon nanomechanical resonators is reported. The structure of resonators is fabricated on a silicon on insulator wafer and transferred to a Tempax glass substrate by anodic bonding. A finite element method simulation has been conducted to investigate the vibration modes of the resonators. Single beam resonator with a length of 21.3 μm, a width of 500 nm, a thickness of 5 μm and the capacitive gap size of about 300 nm shows a nonlinear response. The amplitude of frequency response increases as the frequency is swept upward, and then suddenly jumps to a lower value. The mechanically coupled capacitive silicon nanomechanical resonator with a number of 100 individual beams above is successfully fabricated. Some resonant peaks can be observed, which shows that most nanomechanical resonators are mechanically coupled and synchronised. A mechanical resonance at a high frequency of ∼7.2 MHz in flexural mode has been detected. A small motional resistance of 1.2 kΩ has been achieved by the mechanical coupling.

Engineering of biopolymer ‘partner folds’ that exist in competitive equilibrium with the native state to produce exotic behaviours remains a relatively unexplored area of molecular engineering. Previously, a temperature-sensitive DNA nanodevice that operates by harnessing such a partner fold to implement a thermal band-pass filter was proposed, modelled, and experimentally validated. Due to its peculiar hill-shaped efficiency profile, which differs markedly from the sigmoidal melting curves of simple DNA hairpins, this device could be used to implement temperature-specific control of other molecular machines, and thus represents a promising biotechnological advance. However, no effort was made to examine the detailed dependencies of the peak temperature T ^†, width ΔT ₅₀, and maximum efficiency ε _max on the stabilities of device components. In this work, closed-form expressions for T ^† and ln ε _max are derived and validated. The functional behaviours of these expressions are then examined and harnessed to construct an efficient algorithm for producing designs with target T ^† and ΔT ₅₀ values and optimised ε _max, thereby establishing the feasibility of algorithmic device design. Method effectiveness is validated via production of a target filter, with detailed simulations of device behaviour. Finally, a discussion is presented regarding model effectiveness, extension, and scope.

A new design of complementary metal–oxide–semiconductor microelectromechanical systems (CMOS-MEMS) broadband infrared (IR) emitter arrays with integrated metamaterial absorbers (MAs) developed by the CMOS back-end-of-line is presented. The IR emitter array is a promising broadband thermal radiation source for integrated gas sensors. Novel IR emitter arrays are designed using the Central Semiconductor Manufacturing Corporation 0.5 μm 2-poly-3-metal CMOS process. To improve the low emissivity that is commonly seen in CMOS-MEMS type IR emitters due to the inherited low emissivity of SiO₂ and SiN in CMOS process, we newly adopted tri-layer metal–insulator–metal (MIM) and four-layer insulator–MIM (IMIM) MA by using the CMOS back-end metal layers and inter-layer dielectrics, thereby to excite multi-mode surface plasmon polariton resonances. The emitter integrated with IMIM MA can be electrically modulated up to 344 Hz, as theoretically predicated from thermal properties of the emitters and the radiation properties calculated based on Planck's radiation law. Simulated emissivity spectra through FEM show that the multi-mode resonances in CMOS MIM and IMIM MAs enhance emissivity and broaden the waveband effectively.

To improve the productivity of electronic devices, it is imperative to develop screen-printing techniques that can form finer wires with a higher-aspect ratio. The electric characteristics of conductive wires formed by the proposed screen-printing process combined with an imprinting technique were evaluated. Fine wires with a high-aspect ratio can be realised, owing to the capillary force of parallel-walled structures (PWSs) on polymer films. With the proposed process, printed wires with a line width of only 7.0 µm and an aspect ratio of up to 8.6 were obtained. To optimise the shape of the PWS, the dependence of the shape of PWSs was evaluated electrically. They compared the electric resistance of wires with a width of 10 µm formed using the proposed process to that of 81 µm wires formed using a conventional process. The measured resistance was almost the same, at around 54 kΩ/mm, despite the fact that the proposed process realised wires that were an eighth of the width. By controlling the printing conditions, they confirmed that capillary-effect-based screen-printing is also feasible using highly conductive ink. The resistance of a 13 µm wide printed wire achieved 3.0 Ω/mm.

A simple process to synthesize superhydrophobic surfaces by deep reactive ion etching (DRIE) and polytetrafluoroethylene (PTFE) coating of rectangular grid structures on Si substrate was developed. The Si substrate possesses unique quadrilateral network-type Si microstructures, which when sputtered upon with PTFE, creates a superhydrophobic surface. The fluorinated polymer also exhibited hydrophobic properties where the contact angle of the Si substrate after the PTFE coating was 108.4°. The DRIE etching and PTFE coating together increased the contact angle up to 158.6° for a 40 μm height and 10 × 10 m² area, thus synergistically increasing the hydrophobicity of the surface.

A comprehensive investigation on the superfocusing performance of a plasmonic lens formed by coupled metallic nanoslits is carried out. Based on the geometrical optics and the wavefront reconstruction principle, the nanoslit array for a plasmonic lens is optimally designed to achieve the desired phase modulation by considering the influence of the coupling between adjacent aperiodic nanoslits on phase delay and the theory of periodic metallic nanoslits. The designed lens' focusing behaviour is verified by using the finite-difference time-domain method. Numerical results demonstrate that the superfocusing performance of a plasmonic lens has a close relationship with the lens size, focal length, working medium and incident wavelength. A larger lens size, a shorter focal length, a higher-index working medium can contribute to producing a higher-resolution superfocusing. Moreover, due to the material response, a shorter wavelength is not beneficial for an efficient focusing.

A fine-pitch through-silicon via integration approach with self-aligned back-side benzocyclobutene passivation layer is proposed. Different from the conventional lithographic process, the passivation layer is realised by leveraging plasma etching and chemical-mechanical polishing process. With its well-controlled repeatability, this approach can help reduce the process defect and copper contamination. A plenty of measurement techniques including X-ray radiographic testing, optical and scanning electron microscope observation, four-probe electrical measurement, as well as vector network analyser, are employed in order to verify the fabrication quality and the electrical performances. All the test results support that this fine-pitch through-silicon via integration approach has a promising application prospect.

The optical storage behaviour of InAs quantum dots (QDs) device has been investigated by testing capacitance–voltage (C–V) and current–voltage (I–V) character. Since QDs are embedded in the GaAs quantum well, it can be charged by the spatial separation of electrons and holes. When the device is biased in a storage mode, the optical excitation with the photon energy larger than the energy gap gives rise to a step jump in the responsive current, which is previously stored in the device during the illumination. The holes in the QDs which represent the stored information are storage and deletion by bias. The storage time is on the order of milliseconds as measured by pulsed photovoltage/photocurrent response ratio of the device. The device structure can be used as a photonic memory cell because of long storage time and fast retrieval of photons. Moreover, the memory operation can be carried out by applying a lower voltage.

A process for the fabrication of a capacitive micromachined ultrasonic transducer (CMUT), with a resonance frequency of 2.88 MHz, using an anodically bondable custom-designed low temperature co-fired ceramic (LTCC) substrate with a 60 μm via diameter made of Au is presented. Fabrication of CMUTs with a high fill factor on the LTCC via with a pitch distance of 150 μm is good candidate for medical applications of a miniaturised ring shape CMUT endoscope. Electrical connection between the front side where the device is fabricated and the backside of the LTCC can be achieved with horizontal and vertical interconnects. Investigation of limitations with respect to the device dimensions and experimental fabrication results are discussed. CMUT arrays on LTCC provide a simplified fabrication process with advantages of LTCC architecture compared with typical glass counterparts used in the microelectromechanical systems field.

A new microelectromechanical systems (MEMS) oxygen transporter device to improve the efficacy of islet transplantation to treat type 1 diabetes is described here. The device is fabricated for biocompatibility and designed to maintain islet oxygenation levels throughout the normally hypoxic subcutaneous transplant site. Transplantation of the islets and the device to the subcutaneous location is minimally invasive. Bench-top testing and computational modelling of the device demonstrate that the device can provide sufficient oxygen to prevent hypoxia-induced islet death transplanted subcutaneously. In vitro studies show that the partial oxygen tension is well-maintained using the oxygen transporter in an anoxic environment. In vivo studies using a rat subcutaneous transplant model demonstrate that transplanted islets have more than three-times higher survival using the oxygen transporter compared with transplants not using the transporter, two weeks post-transplant. In addition, histology sections show well-maintained islet structures one month after transplantation for islets transplanted in the presence of the device. Our MEMS oxygen transporter is a novel and promising device to support the efficacy of subcutaneous islet transplantation as a potential cure for type 1 diabetes.

The obtained results on application of the carbon nanotubes (CNTs) in lubricating oils for UAZ 31512 engine are presented. The calculation results showed that the thermal conductivity of lubricating oils increase about 10% when using lubricating oil with 0.12 vol% of CNTs concentration. The experimental results on Ulyanovskiy Avtomobilnyi Zavod 31512 (UAZ 31512) engine on pedestal at free load showed that the temperature of engine dropped about 10°C and the fuel saving was up to 10% when using lubricating oil with 0.12 vol% of CNTs concentration.

A spray-coating method for cyclic olefin copolymer (COC) electret material with polystyrene (PS) nanoparticles is developed here. Compared with the traditional polymer electret materials, the COC electrets with PS nanoparticles achieved better surface charge stability when exposed to harsh environment at high humidity or high temperature. With the spray coating technique, they can easily control the thickness of the electret layer. The surface charge stability of the electret has been detailed studied with various concentrations of the nanoparticles. They have also applied the spray coated electret to electrostatic energy harvesting devices. The experiments confirmed that the energy harvesting devices can generate more stable power output using the spray coated electret with nanoparticles.

A method of picking up carbon nanotubes (CNTs) from nanotube bulk by van der Waals force inside a scanning electron microscopy is presented. An atomic force microscope cantilever was employed as end effector of nanorobotics manipulators for CNT picking up. A manipulation strategy was established by analysing the van der Waals force of three different types of contacting models. Three groups of experiments were designed and carried out to investigate the effects of different factors. Factors including pickup angle, pickup contact area between the CNT and the cantilever and pickup speed of the end effector were discussed. The results shown that a pickup angle at 90.1° and a pickup speed lower than 10 nm/step with a pickup contact length more than 1.5 µm would increase the probability of picking up CNT successfully.

A simple printing process to design a novel piezoelectric energy-harvesting device made from vinylidene fluoride/trifluoroethylene copolymers is presented. Fabrication using a metal nanoink and a household printer dramatically reduced the fabrication complexity. In addition, this process employed low-temperature steps, and thus the structural damage to the polymers resulting from high-temperature annealing was avoided. By stacking the devices and connecting them in parallel, the generated energy was increased and electric power of ∼1.12 μJ was obtained.

The salient features of microfluidics such as reduced cost, handling small sample and reagent volumes and less time required to fabricate the devices has inspired the present work. The incompatibility of three-dimensional printer resins in their native form and the method to improve their compatibility to many biological processes via surface modification are reported. The compatibility of the material to build microfluidic devices was evaluated in three different ways: (i) determining if the ultraviolet (UV) cured resin inhibits the polymerase chain reaction (PCR), i.e. testing devices for PCR compatibility; (ii) observing agglutination complex formed on the surface of the UV cured resin when anti-C-reactive protein (CRP) antibodies and CRP proteins were allowed to agglutinate; and (iii) by culturing human embryonic kidney cell line cells and testing for its attachment and viability. It is shown that only a few among four in its native form could be used for fabrication of microchannels and that had the least effect on biological molecules that could be used for PCR and protein interactions and cells, whereas the others were used after treating the surface. Importance in building lab-on-chip/micrototal analysis systems and organ-on-chip devices is found.