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Crystallization of polyamide 12 (PA12) is an essential process requiring thorough investigation for evaluating the mechanical properties after the polymer parts are manufactured. The change in crystallization temperature results in different crystallization behaviors for PA12. Hence, the crystal morphology of PA12 achieved provides important information about crystallization behavior, especially for those produced through additive manufacturing due to its heterogenous cooling rate in a single print bed. Considering the need of investigating PA12 crystallization using phase-field modeling, this paper aims to simulate the spherulite morphology of PA12 undergoing isothermal crystallization. This model is compared with the spherulite morphologies obtained from the optical microscopy test. The model shows that PA12 spherulites have thicker dendrites when the isothermal temperature is higher. The present phase-field model can determine the spherulite morphologies of bulk printed PA12 based on the crystallization condition and be used to evaluate the properties of the printed part. Nanyang Technological University This research work is conducted in collaboration with HP Inc. and supported by Nanyang Technological University and the Singapore Government through the Industry Alignment Fund–Industry Collaboration Projects Grant (I1801E0028).

Soil-water characteristic curve (SWCC) correlates the water content of a soil to its soil suction, which is a very important property of unsaturated soils. Osmotic tensiometers (OTs) have shown their capability in high soil suction measurement. This study tried to use OT combined with a pressure plate and WP4C dewpoint potentiometer to determine the SWCC of a residual soil. Three OTs with different measuring ranges (900 kPa, 1200 kPa, 2300 kPa) were prepared for soil suction measurement. The temperature effect on the pressure variations of OTs was illustrated based on Flory-Huggins polymer theories and an appropriate calibration equation was proposed to eliminate the temperature effect on the accuracy of soil suction measurement using OT. The OT showed a fast response in soil suction measurement and the equilibrium can be established in 10–15 min during SWCC measurement. Comparison of the SWCC data obtained from the pressure plate, OT, and WP4C dewpoint potentiometer proves that the OT had good performance in the determination of SWCC, especially for the transition zone (i.e., 10–1500 kPa suction range), by providing more data points to define the SWCC in a shorter period. The results show that the usage of OT will shorten the time required for the determination of SWCC and could be considered as a new and reliable technique in SWCC measurement. Submitted/Accepted version

An adaptive phase-field modeling approach is developed for the dynamic brittle fracture of composite materials subjected to impact loading. This approach is capable of capturing the dynamic fracture patterns in composite materials including matrix cracking, delamination between adjacent plies, and interaction between the two failure modes via the exploitation of interface and crack phase fields. The driving force for the crack evolution is derived by introducing the contributions of the longitudinal and transverse damage considering the tension–compression asymmetry. Moreover, an anisotropic crack surface density function is introduced by considering the material anisotropy induced by fibers. The computational efficiency of the dynamic fracture modeling is improved via the adaptive mesh refinement strategy within the framework of the isogeometric-meshfree approach. The Newmark implicit integration scheme is used for the temporal discretization of the phase-field governing equations. Finally, simulations of both mode-I and mixed-mode fracture, such as the dynamic branching and the three-point bending tests, are implemented for homogeneous materials and composites, which demonstrates the reliability of the developed approach. Nanyang Technological University The authors would like to acknowledge the financial support from Nanyang Technological University.

With the capability to build components with freeform geometries, laser powder bed fusion (L-PBF) is considered as one of the most promising techniques for industrial applications. Compared to conventional manufacturing technologies, an additional advantage of L-PBF process is the capability to fabricate parts with multiple materials, such as in-situ alloying and functionally graded alloys. In this regard, here we present a computational model to simulate the L-PBF of multiple materials. Based on volume of fluid (VOF) methods and computational fluid dynamics (CFD), the multi-physics multi-material model was successfully implemented with various physics of L-PBF process, including surface tension, Marangoni shear force, recoil pressure, compositional diffusion, etc. In addition, we demonstrated the numerical algorithm of ray tracing heat source for multiple materials. With reasonable assumptions, conduction mode or keyhole mode laser melting of miscible materials can be simulated via the proposed computational framework. Furthermore, such multi-physics model is capable of simulating L-PBF of an arbitrary number of materials. The computational model can help achieve insightful understanding of the L-PBF of multiple materials. National Research Foundation (NRF) The authors acknowledge the support by the National Research Foundation, Prime Minister’s Office, Singapore under its Medium Sized center funding scheme.

Compared with conventional water-filled tensiometers, polymer-filled osmotic tensiometers (OTs) can measure a higher matric suction by increasing the osmotic pressure of the water inside the tensiometer. The measuring range of OT is equal to the osmotic pressure of water inside the OT. All previous research used commercial polymers in developing OTs and the mechanism of long-term pressure decay of OTs was not found. In this study, polymers including polyacrylamide (PAM) and sodium polyacrylate (NaPA) with different degrees of crosslinking were synthesised by UV polymerisation to develop new OTs. Long-term pressure variations of OTs indicated that the pressure decay was more likely due to the stress relaxation of polymer materials instead of polymer leakage. PAM-filled OTs have a faster stress relaxation behaviour than NaPA-filled OTs so that they can keep constant pressure (i.e., constant measuring range) for a long time and there is no need for pressure correction based on the pressure decay rate. However, the measuring range of PAM-filled OTs is lower than that of NaPA-filled OTs. The result of matric suction measurements demonstrated that the proposed OTs can be used to measure matric suction both in low and high ranges with fast response and high accuracy. Nanyang Technological University National Parks Board Submitted/Accepted version The authors would like to acknowledge the financial support from Nanyang Environment and Water Research Institute (NEWRI), Interdisciplinary Graduate School, Nanyang Technological University, Singapore, as well as the National Parks Board, Singapore.

Chinese sturgeon (Acipenser sinensis) has been listed as a critically endangered species on the IUCN Red List and is an endemic fish of China. Five sets of duplex polymerase chain reactions (PCR) assays were developed with 10 tetranucleotide microsatellites for Chinese sturgeon. The size of CS57, ZHX43, ZHX69, AS105, ZHX51, AS074, ZHX2, AS078, AS026 and AS073 products in 184 Chinese sturgeon individuals ranged from 257–305, 191–241, 251–285, 172–244, 236–260, 169–209, 194–234, 92–176, 165–257 and 120–164, respectively. The observed allele number of the 10 microsatellites ranged from 7 to 16, and the total number of alleles was 106. The number of alleles per individual in CS57, ZHX43, AS105, AS074, AS078 and AS026 was 1–4. The number of alleles per individual in ZHX69, ZHX51, ZHX2 and AS073 was 2–4. The mean number of alleles per locus per individual ranged from 2.01–3.76. The expected heterozygosity (HE), observed heterozygosity (HO), polymorphic information content (PIC) and Shannon-Weiner diversity index (H′) ranged from 0.582 to 0.899, from 0.676 to 1, from 0.518 to 0.886 and from 1.034 to 2.34, respectively. Despite many advantages, the use of microsatellites as genetic analysis tools can be limited by the cost of the associated experiment. To solve this problem, this set of five duplex PCRs will provide tools that are more helpful, less expensive and less time consuming than others used for genetic analyses in Chinese sturgeon.

Reconstructing of cell architecture plays a vital role in tissue engineering. Recent developments of self-assembling of cells into three-dimensional (3D) matrix pattern using surface acoustic waves have paved a way for a better tissue engineering platform thanks to its unique properties such as nature of noninvasive and noncontact, high biocompatibility, low-power consumption, automation capability, and fast actuation. This article discloses a method to manipulate the orientation and curvature of 3D matrix pattern by redesigning the top wall of microfluidic chamber and the technique to create a 3D longitudinal pattern along preinserted polydimethylsiloxane (PDMS) rods. Experimental results showed a good agreement with model predictions. This research can actively contribute to the development of better organs-on-chips platforms with capability of controlling cell architecture and density. Meanwhile, the 3D longitudinal pattern is suitable for self-assembling of microvasculatures. Ministry of Education (MOE) Nanyang Technological University The authors gratefully acknowledge the support of (i) Nanyang Technological University and the Ministry of Education of Singapore through a PhD Scholarship; and (ii) the Academic Research Fund (AcRF) Tier 1 Grants (RG 96/18).

Warpage of printed parts, especially for multi-jet fusion (MJF) process, is believed to have strong correlation with crystallization shrinkage. Hence, this article investigates the shrinkage phenomenon of polyamide-12 (PA12) during crystallization process. Various cooling rates show that PA12 exhibits different crystallization behaviour, which affect the crystallinity, crystal phase and crystal shrinkage when performed in MJF. The investigation shows that crystallization shrinkage of PA12 coincides with the exothermic reaction of crystallization process. With cooling rate as slow as 0.2 °C/min, PA12 sample shrinks 1.64% during the crystallization process with crystallinity calculated at 24.9%. X-ray diffraction (XRD) suggests shrinkage are closely related to lamellar folding and growth of γ crystal phase within PA12 samples during crystallization. Spherulites are found to be smaller in diameter with faster cooling rate. These investigations provide detailed understanding of the crystallization behaviour of PA12 for MJF process. Submitted/Accepted version This research work is supported under the RIE2020 Industry Alignment Fund – Industry Collaboration Projects (IAF-ICP) Funding Initiative (I1801E0028), as well as cash and in-kind contribution from the industry partner, HP Inc.

Precise, automatic and reliable position control of micro-objects such as single particles, biological cells or bio-organisms is critical for applications in biotechnology and tissue engineering. However, conventional acoustofluidic techniques generally lack reliability and automation capability thus are often incapable of building an efficient and automated system where the biological cells need to be precisely manipulated in three dimensions (3D). To overcome these limitations, we developed an acoustofluidic closed-loop control system which is combined with computer vision techniques and standing surface acoustic waves (SSAWs) to implement selective, automatic and precise position control of an object, such as a single cell or microparticle in a microfluidic chamber. Position of the object is in situ extracted from living images that are captured from a video camera. By utilizing the closed-loop control strategy, the object is precisely moved to the desired location in 3D patterns or along designed trajectories by manipulating the phase angle and power signal of the SSAWs. Controlling of breast cancer cells has been conducted to verify the principle and biocompatibility of the control system. This system could be employed to build an automatic system for cell analysis, cell isolation, self-assembling of materials into complex microstructures, or lab-on-chip and organ-on-chip applications. Ministry of Education (MOE) Nanyang Technological University The authors gratefully acknowledge the support of (i) Nanyang Technological University and the Ministry of Education of Singapore through a PhD Scholarship; (ii) the UK Engineering and Physical Sciences Research Council (EPSRC) grants EP/P018998/1; (iii) Special Interesting Group of Acoustofluidics funded by UK Fluids Network (EP/N032861/1).

Manipulating biological cells or microparticles in three dimensions (3D) is invaluable for many biomedical applications, and recently effective and rapid manipulations of microparticles in 2D and 3D within microchannels or chambers using surface acoustic waves (SAWs) with bulk piezoelectric materials have been reported. However, these are generally expensive, or brittle and cannot be easily integrated into a single lab-on-chip. In this paper, we realized microparticle/cell patterning and 3D manipulation of yeast cells inside a chamber with a height of 1 mm using thin film ZnO/Si SAW devices. Effects of SAW frequency, channel width and thickness on alignment of microparticles were firstly investigated, and positions of the microparticles in the direction of SAW propagation can be controlled precisely by changing the phase angle of the acoustic waves from the ZnO/Si SAW device. A numerical model has been developed to investigate the SAW acoustic field and the resulted 3D motions of microparticles under the acoustic radiation forces within the microchamber. Finally, we realized and observed the 3D patterning of yeast cells within the microchannel. Our work shows a great potential for acoustofluidic, neural network research and biomedical applications using the ZnO/Si SAW devices. Accepted version

Sterlet (Acipenser ruthenus) is an important economic fish because of its nourishing caviar, isinglass and flesh. In order to facilitate the recovery of this species, the full understanding of its population genetic structure is necessary for taking appropriate management actions. However, genetic data on the use of nuclear loci in sterlet is still quite poor because microsatellite markers in sterlet that had been developed appeared to be polyploidy which add difficulties in studying the genetic of the sterlet. In this study, 24 tetranucleotide microsatellite markers were developed in sterlet from 160 microsatellite markers of the endangered Chinese sturgeon (Acipenser sinensis). Ten (ZHX76, ZHX64, Z194, Z217, Z184, Z242, Z250, Z258, Z268 and Z269) of the 24 loci showed disomic patterns while the rest loci showed tetrasomic patterns. In this paper, 24 microsatellite markers were characterized in 16 sterlet individuals and all of them were polymorphic with 2 to 7 alleles per locus. The Hardy-Weinberg departure value (d), polymorphic information content (PIC), the observed heterozygosity (HO), the Shannon-Wiener Diversity Indices (H') and the mean expected heterozygosity (HE) of all 24 polymorphic loci ranged from -0.334 to 0.484, 0.367 to 0.725, 0.438 to 1, 0.659 to 1.695, from 0.466 to 0.777, respectively. The markers described here will help in addressing practical problems such as the study of population genetics, conservation genetics and evolution in the polyploidy derivative nature of sterlet.

Chinese sturgeon (Acipenser sinensis), a critically endangered Acipenseridae family member, is one of the largest anadromous, native fish in China. Numerous research programmes and protection agencies have focused on breeding and preserving this endangered species. However, available information is limited on the different stages of sex development, especially on the reproductive regulation of the hypothalamus-pituitary-gonad (HPG) axis of A. sinensis. To unravel the mechanism of gene interactions during sex differentiation and gonad development of A. sinensis, we performed transcriptome sequencing using HPG samples from male and female A. sinensis in two developmental stages. In this study, 271.19 Gb high-quality transcriptome data were obtained from 45 samples belonging to 15 individuals (six in stage I, six males and three females in stage II). These transcriptomic data will help us understand the reproductive regulation of the HPG axis in the development stages of A. sinensis and provide important reference data for genomic and genetic studies in A. sinensis and related species., Design Type(s)development or differentiation design • transcription profiling design • sequence assembly objective • sequence annotation objectiveMeasurement Type(s)transcription profiling assayTechnology Type(s)RNA sequencingFactor Type(s)sex • developmental stageSample Characteristic(s)Acipenser sinensis • pituitary gland • Hypothalamus • Gonad Machine-accessible metadata file describing the reported data (ISA-Tab format)

Integrated sensors in fitness and sports equipment have been developed in the last two decades. A zinc oxide (ZnO) thin film could be a suitable material for such applications due to its excellent physical and piezoelectric properties. In this paper, nanocrystalline ZnO films were deposited on silicon (Si) wafers with different substrate tilt angles (30° to 75°) and sputtering durations (2 to 4 h) using RF magnetron sputtering at room temperature. ZnO thin film topographical properties, film thickness (0.8 to 3.7 μm) and columnar inclined angle (14° to 34°) on the different locations of specimens were characterised by scanning electron microscope (SEM). Simulation and experimental results from the sensor arrays were also fabricated using fabrication techniques compatible with a standard micromachining process. The simulation and experiments for sensor arrays proved that sensor arrays were capable of distinguishing the differences of contact force values, contact locations and directions. Moreover, ZnO thin film micro-cantilevers were fabricated and tested by an AC impedance technique and a laser doppler vibrometer (LDV). The results exhibited good piezoelectric properties of shear-mode ZnO thin film driven cantilevers. Keywords: Zinc oxide, Thin films, RF sputtering, Shear mode

A method based on standing surface acoustic waves (SSAWs) is proposed to pattern and manipulate microparticles into a three-dimensional (3D) matrix inside a microchamber. An optical prism is used to observe the 3D alignment and patterning of the microparticles in the vertical and horizontal planes simultaneously. The acoustic radiation force effectively patterns the microparticles into lines of 3D space or crystal-lattice-like matrix patterns. A microparticle can be positioned precisely at a specified vertical location by balancing the forces of acoustic radiation, drag, buoyancy, and gravity acting on the microparticle. Experiments and finite-element numerical simulations both show that the acoustic radiation force increases gradually from the bottom of the chamber to the top, and microparticles can be moved up or down simply by adjusting the applied SSAW power. Our method has great potential for acoustofluidic applications, building the large-scale structures associated with biological objects and artificial neuron networks. MOE (Min. of Education, S’pore) Published version

The authors acknowledge support from the Innovative electronic Manufacturing Research Centre (IeMRC) through the EPSRC funded flagship project SMART MICROSYSTEMS (FS/01/02/10), Knowledge Transfer Partnership No KTP010548, EPSRC project EP/L026899/1, EP/F063865/1; EP/F06294X/1, EP/P018998/1, the Royal Society-Research Grant (RG090609) and Newton Mobility Grant (IE161019) through Royal Society and NFSC, the Scottish Sensing Systems Centre (S3C), Royal Society of Edinburgh, Carnegie Trust Funding, Royal Academy of Engineering-Research Exchange with China and India, UK Fluidic Network and Special Interest Group-Acoustofluidics, the EPSRC Engineering Instrument Pool. We also acknowledge the National Natural Science Foundation of China (Nos. 61274037, 51302173), the Zhejiang Province Natural Science Fund (No. Z11101168), the Fundamental Research Funds for the Central Universities (No. 2014QNA5002), EP/D03826X/1, EP/ C536630/1, GR/T24524/01, GR/S30573/01, GR/R36718/01, GR/L82090/01, BBSRC/E11140. ZXT acknowledges the supports from the National Natural Science Foundation of China (61178018) and the NSAF Joint Foundation of China (U1630126 and U1230124) and Ph.D. Funding Support Program of Education Ministry of China (20110185110007) and the NSAF Joint Foundation of China (Grant No. U1330103) and the National Natural Science Foundation of China (No. 11304209). NTN acknowledges support from Australian Research Council project LP150100153. This work was partially supported by the European Commission through the 6th FP MOBILIS and 7th FP RaptaDiag project HEALTH-304814 and by the COST Action IC1208 and by the Ministerio de Economia y Competitividad del Gobierno de Espana through projects MAT2010-18933 and MAT2013-45957R.

The surge in popularity of lab-on-chip applications has set a new challenge for the fabrication of prototyping devices, such as electrokinetic devices. In such devices, a micro-electrode is the key component. Currently, microelectromechanical systems (MEMS) processes such as lift-off and etching techniques are employed to prepare the micro-sized conductive patterns. These processes are time-consuming, require a material removal step, clean-room facilities, and the utilisation of harmful chemicals. On the other hand, rapid fabrication is required by researchers designing such devices to test their functionality. Additive manufacturing technology such as the inkjet printing of conductive material is one potential solution to achieve that objective. In this study, we report the utilisation of inkjet printing for the rapid prototyping of alternating current (AC) electrokinetic devices on a rigid glass substrate. The non-lithographical and vacuum-free process for the fabrication of a microfluidic device was demonstrated. The smallest feature size of 60 μm was successfully printed. The crystalline structure of the printed material under different curing temperatures was characterised. It was found that these treatment conditions affect electrical conductivity. Although a low-temperature sintering process was applied, low resistivity was obtained. An AC electrokinetics device for the manipulation of microparticles has been prepared to illustrate such printed silver micro-patterns. The results strongly support the idea that inkjet printing is a powerful and cost-effective prototyping tool for researchers who work with electrokinetic devices. ASTAR (Agency for Sci., Tech. and Research, S’pore) MOE (Min. of Education, S’pore) Published version

Zinc oxide (ZnO) thin film piezoelectric microelectromechanical systems (MEMS) based vibration energy harvesters with two different designs are presented. These harvesters consist of a silicon cantilever, a silicon proof mass, and a ZnO piezoelectric layer. Design I has a large ZnO piezoelectric element and Design II has two smaller and equally sized ZnO piezoelectric elements; however, the total area of ZnO thin film in two designs is equal. The ZnO thin film is deposited by means of radio-frequency magnetron sputtering method and is characterized by means of XRD and SEM techniques. These ZnO energy harvesters are fabricated by using MEMS micromachining. The natural frequencies of the fabricated ZnO energy harvesters are simulated and tested. The test results show that these two energy harvesters with different designs have almost the same natural frequency. Then, the output performance of different ZnO energy harvesters is tested in detail. The effects of series connection and parallel connection of two ZnO elements on the load voltage and power are also analyzed. The experimental results show that the energy harvester with two ZnO piezoelectric elements in parallel connection in Design II has higher load voltage and higher load power than the fabricated energy harvesters with other designs. Its load voltage is 2.06 V under load resistance of 1 MΩ and its maximal load power is 1.25 μW under load resistance of 0.6 MΩ, when it is excited by an external vibration with frequency of 1300.1 Hz and acceleration of 10 m/s2. By contrast, the load voltage of the energy harvester of Design I is 1.77 V under 1 MΩ resistance and its maximal load power is 0.98 μW under 0.38 MΩ load resistance when it is excited by the same vibration. Published version

To realize higher areal densities in hard disk drive (HDD), it is necessary to decrease distance between slider and disk, i.e. flying height. The low flying height may result in severe damage occurring on the head-disk interface. Therefore, it is essential to monitor head-disk interactions to prevent instability and damage. In this paper, a smart slider integrated with micro-sensor and micro-actuator is proposed. The fabrication and characterization of the smart slider with integrated zinc oxide (ZnO) thin-film sensor and actuator is presented here. A possible 3D printing manufacturing approach is also proposed to replace the current complex MEMS fabrication processes for producing the smart slider. Published version

Integrated capability for detection of head-disk contact is desired for magnetic sliders with near-contact flying height. At the same time, fabrication of added features should be compatible with the existing slider micromachining process which is highly specialized and cost sensitive. Aimed at meeting the two requirements, a novel sensor configuration is explored in the present study. The new sensor configuration consists of a piezoelectric zinc oxide (ZnO) thin-film sensor sandwiched in the magnetic slider on its trailing side. Coupled structural and piezoelectric finite-element analysis for a sensor-slider- suspension assembly was performed to investigate the dynamic sensing performance. Output voltages on the millivolt level were obtained under typical head-disk interactions. The 2nd in-plane bending mode of the slider was found to be the major contributor to the output voltage. Parametric study showed that a thicker ZnO layer generally generated a larger output, while the thickness of the slider overcoat only had minimal effect. Simulation results from harmonic and transient analyses demonstrated that the piezoelectric thin-film ZnO sensor is sufficiently sensitive for detection of head-disk contact. Accepted version

An efficient and stable quantum dot light-emitting diode (QLED) with double-sided metal oxide (MO) nanoparticle (NP) charge transport layers is fabricated by utilizing the solution-processed tungsten oxide (WO3) and zinc oxide (ZnO) NPs as the hole and electron transport layers, respectively. Except for the electrodes, all other layers are deposited by a simple spin-coating method. The resulting MO NP-based QLEDs show excellent device performance, with a peak luminance of 21300 cdm-2 at the emission wavelength of 516 nm, a maximal current efficiency of 4.4 cdA-1 and a low turn-on voltage of 3 V. More importantly, with the efficient design of the device architecture, these devices exhibit a significant improvement in device stability and the operational lifetime of 95 h measured at room temperature can be almost 20-fold longer than that of the standard device. NRF (Natl Research Foundation, S’pore) ASTAR (Agency for Sci., Tech. and Research, S’pore)

Previous studies on zinc oxide (ZnO) microcantilevers have been focused on applications in the atomic force microscopy (AFM). Characteristics of ZnO microcantilever actuators were not thoroughly investigated in those studies. This paper reports modeling, fabrication and characterization of a piezoelectric ZnO microcantilever actuator for high-frequency nanopositioning. Main characteristics of the ZnO microcantilever, i.e. resonant frequency, actuation sensitivity and force-deflection relationship, have been studied by modeling and experiments. Analytic equations of the resonant frequency and actuation sensitivity were derived. Tip deflection as a function of driving voltage and external load was formulated. Effects of major geometric dimensions on the performance of piezoelectric ZnO cantilevers were demonstrated with numerical results. A prototype was designed for applications requiring micro-Newton actuation forces with driving frequencies above 10 kHz. The microfabricated cantilever was characterized for its resonant frequency and actuation sensitivity. Impedance analysis identified the resonant frequency at 53 kHz which was in excellent agreement with the frequency response function. Steady-state actuation sensitivity at 15 kHz was found to be 12 nm/V with a bandwidth of 27 kHz. Accepted version

The modification of zinc oxide (ZnO) with silver (Ag) has proven to be an effective strategy to enhance the optical and electrical properties, in which the interactions between ZnO and Ag are critically determined by the structure and morphology of the ZnO–Ag hybrids. In order to achieve homogeneous and controllable distribution, polydopamine (PDA) was introduced via in situpolymerization to assist the decoration of ZnO nanorods (NRs) with Ag nanoparticles (NPs). Compared with pristine ZnO NRs, the light absorption is significantly enhanced for the PDA assisted Ag-decorated ZnO, which is attributed to the Ag NPs as well as the carbonized PDA thin film. Ag NPs of small size enhance the multiple/high-angle scattering from localized plasmonic effect, which increases the light path length hence traps more light. The carbonized PDA film is further beneficial to the absorption of the visible light. The Ag-decorated ZnO NRs on fluorine-doped tin oxide (FTO) coated glasses were then used as photoanodes of the photoelectrochemical (PEC) cell. The short circuit current density (JSC, 1.8 mA cm−2), maximum photo current conversion efficiency (PCE, 3.9%) and lifetime (3.07 mA cm−2 at 500 seconds) are achieved with an optimized loading of Ag nanoparticles derived from 0.01 M silver nitrate (AgNO3), which are found to be much higher than those of pristine ZnO NRs and other reported Ag–ZnO-based photoanodes. The overall PEC performance improvement is attributed to the localized plasmonic effect enhanced light harvesting as well as the facilitated charge transport and inhibition of recombination of electrons and holes from both Ag nanoparticles that act as an electron acceptor and carbonized PDA film as stabilizer and separator. Published version

Zinc oxide (ZnO) nanorods coated with silver (Ag) film on a polyethylene terephthalate (PET)flexible substrate were used as the photo anode for water splitting. The hybrid nanostructures were prepared via low-temperature hydrothermal growth and electron beam evaporation. The effects of plasmonic enhanced absorption, surface recombination inhibition and improved charge transport are investigated by varying the Ag thickness. Light trapping and absorption enhancement are further studied by optimizing the curvature of the PET substrates. The maximum short circuit current density (JSC, 0.616 mA cm -2) and the photoelectron conversion efficiency (PCE, 0.81%) are achieved with an optimized Ag film thickness of 10 nm and substrate bending radius of 6.0 mm. The maximum JSC and PCE are seven times and ten times, respectively, higher than those of the bare ZnO nanorods on flexible substrates without bending. The overall PEC performance improvement is attributed to the plasmonic effects induced by Ag film and improved charge transport due to inhibition of ZnO surface charge recombination. Enhanced light trapping (harvesting) induced by bending the PET substrates further improved the overall efficiency.

A hollow microtube–nanowire structure of carbon-doped ZnO was fabricated via using carbon fibers as the sacrificed substrates. The hollow microtube–nanowire architecture was characterized by scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Raman, photoluminescence and electrical measurements. The results indicate that carbon is self-doped into ZnO primarily substituting oxygen in the growth and annealing processes. The room temperature photoluminescence spectrum of the carbon-doped ZnO shows a strong defect-induced emission in the visible range of 400–800 nm. The optoelectronic properties in the range of the visible light are demonstrated by operating an organic/inorganic p–n heterojunction and a metal–semiconductor–metal (M–S–M) structure, which indicates that carbon doping in ZnO extends its photoelectric specifics in the visible light region.

A micro silicon cantilever actuated by ZnO thin film was designed, fabricated and characterized. The ZnO thin film was deposited by RF sputtering at room temperature. The transverse piezoelectric constant d31 was found to be-4.66 pC/N. Time and frequency responses of the cantilever actuator were investigated by means of a laser Doppler vibrometer. The actuator has a sensitivity of 12 nm/V at 15 kHz. Its 1st bending resonance was observed at 53 kHz. The bandwidth was found to be 27 kHz with damping of 0.35%. The cantilever demonstrated capability of high frequency actuation on a nanometer level.

In this work, piezoelectric zinc oxide (ZnO) thin films are deposited under different deposition conditions using RF magnetron sputtering method. The influence of RF power, O2/(Ar + O2) gas ratio and sputtering pressure on the deposition rate, crystalline structures, surface roughness and composition purity of ZnO film are investigated by X-ray Diffractometer (XRD), scanning electron microscopy (SEM), atom force microscopy (AFM) and energy dispersive X-ray spectroscopy (EDS). All the fabricated ZnO films have a preferred ZnO(0 0 2) orientation. When the gas ratio of O2/(Ar + O2) is 25% and the working pressure is 0.8 Pa, the grain size in the ZnO thin film is of the largest and the ZnO film has a very smooth and dense surface. The SEM cross-sectional image of the ZnO film confirms that the ZnO thin film has a columnar structure and the c-axis is perpendicular to the substrate surface. The EDS analysis shows the ZnO film has only Zn and O elements. Different ZnO film based piezoelectric micro cantilevers are fabricated using micromachining techniques and the dynamic response of these piezoelectric cantilevers are measured by laser Doppler vibrometer (LDV). The tested results from LDV show that the deflection of the piezoelectric cantilever is linear with the driving voltage. The transverse piezoelectric constant d31 of the ZnO thin film deposited under best conditions is calculated as −3.21 pC/N by the LDV data. This value is higher than other published works. In future, these ZnO thin films will be used in our ongoing project for the design, simulation and fabrication of smart slider with a built-in ZnO sensor/actuator in the hard disk drives.

Hollow hemispheric ZnO shells/cages are synthesized on graphite fiber via simple thermal evaporation process. The cage-like ZnO structures exhibit micron or submicron size and hollow hemispheric shape with polycrystalline shell made of the ZnO nanocrystals. Controlled time-sequenced growth experiment is conducted to interpret the growth process, which indicates that the growth mechanism of the hollow hemispheric ZnO shells/cages involves formation of Zn particles firstly, followed by oxidation of the outer surface of Zn droplets and meantime sublimation of the core Zn.