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Optical resonances in bipartite metal nanostructure lattices are more resilient to finite size-effects than equivalent unipartite lattices, but the complexities of their behaviour in non-ideal settings remain relatively unexplored. Here we investigate the quality factor and extinction efficiency of 1D Ag and Au unipartite and bipartite lattices. By modelling finite size lattices over a range of periods we show that the quality factor of Ag bipartite lattices is significantly better than unipartite lattices. This improvement is less pronounced for Au bipartite lattices. We also show that bipartite lattices are dramatically affected by structure size variations at scales that are typically seen in electron beam lithography fabrication in contrast to unipartite lattices, which are not as sensitive.

Mechanical forces shape physiological structure and function within cell and tissue microenvironments, during which cells strive to restore their shape or develop an adaptive mechanism to maintain cell integrity depending on strength and type of the mechanical loading. While some cells are shown to experience permanent plastic deformation after a repetitive mechanical tensile loading and unloading, the impact of such repetitive compression on plastic deformation of cells is yet to be understood. As such, the ability to apply cyclic compression is crucial for any experimental setup aimed at the study of mechanical compression taking place in cell and tissue microenvironments. Here, we demonstrate such cyclic compression using a microfluidic compression platform on live cell actin in SKOV-3 ovarian cancer cells. Live imaging of the actin cytoskeleton dynamics of the compressed cells was performed for varying pressures applied sequentially in ascending order during cell compression. Additionally, recovery of the compressed cells was investigated by capturing actin cytoskeleton and nuclei profiles of the cells at zero time and 24 h-recovery after compression in end point assays. This was performed for a range of mild pressures within the physiological range. Results showed that the phenotypical response of compressed cells during recovery after compression with 20.8 kPa differed observably from that for 15.6 kPa. This demonstrated the ability of the platform to aid in the capture of minute differences in cell behaviour as a result of being compressed at various pressures in physiologically relevant manner. Differences observed between compressed cells fixed at zero time or after 24 h-recovery suggest that SKOV-3 cells exhibit deformations at the time of the compression, a proposed mechanism cells use to prevent mechanical damage. The extent of recovery of compressed cells, inferred by imaging cell membrane bulges and actin cytoskeleton and measuring the shape descriptors of cell nuclei, can give insights into the plasticity of cancer cells. Thus, biomechanical responses of SKOV-3 ovarian cancer cells to sequential cyclic compression and during recovery after compression could be revealed in a flexible microdevice. As demonstrated in this work, the microfluidic platform could control the strength and duration of cyclic compression, while enabling the observation of morphological, cytoskeletal and nuclear changes and recovery in compressed cells, thus providing a powerful new tool for the study of mechanobiological processes in cancer and cell biology.

Appropriate mechanical forces on cells are vital for normal cell behaviour and this review discusses the possibility that tumour initiation depends partly on the disruption of the normal physical architecture of the extracellular matrix (ECM) around a cell. The alterations that occur thence promote oncogene expression. Some questions, that are not answered with certainty by current consensus mechanisms of tumourigenesis, are elegantly explained by the triggering of tumours being a property of the physical characteristics of the ECM, which is operative following loading of the tumour initiation process with a relevant gene variant. Clinical observations are consistent with this alternative hypothesis which is derived from studies that have, together, accumulated an extensive variety of data incorporating biochemical, genetic and clinical findings. Thus, this review provides support for the view that the ECM may have an executive function in induction of a tumour. Overall, reported observations suggest that either restoring an ECM associated with homeostasis or targeting the related signal transduction mechanisms may possibly be utilised to modify or control the early progression of cancers. The review provides a coherent template for discussing the notion, in the context of contemporary knowledge, that tumourigenesis is an alliance of biochemistry, genetics and biophysics, in which the physical architecture of the ECM may be a fundamental component. For more definitive clarification of the concept there needs to be a phalanx of experiments conceived around direct questions that are raised by this paper.

Solvents play an important role in the preparation of the electron ETL and hole HTL transport layers and consequently in determining the optical properties, morphologies and perovskite thin-film quality. Lithium TFSI employed in HTL and FK209 cobalt TFSI used in ETL are usually dissolved by acetonitrile (ACN) solvent. However, this solvent is toxic and can accelerate the deterioration of the perovskite films. This work propose alternatives for ACN to slow down the perovskite films deterioration and improve its performance. Solar cells prepared using FK209/ethanol and lithium/isopropanol alcohol have shown excellent performance with champion device efficiency reaching 23.5%.

Evidence continues to emerge that cancer is not only a disease of genetic mutations, but also of altered mechanobiological profiles of the cells and microenvironment. This mutation-independent element might be a key factor in promoting development and spread of cancer. Biomechanical forces regulate tumor microenvironment by solid stress, matrix mechanics, interstitial pressure and flow. Compressive stress by tumor growth and stromal tissue alters the cell deformation, and recapitulates the biophysical properties of cells to grow, differentiate, spread or invade. Such a solid stress can be introduced externally to change the cell response and to mechanically induce cell lysis by dynamic compression. In this work we report a microfluidic cell-culture platform with an integrated, actively-modulated actuator for the application of compressive forces on cancer cells. Our platform is composed of a control microchannel in a top layer for introducing external force and a polydimethylsiloxane (PDMS) membrane with monolithically integrated actuators. The integrated actuator, herein called micro-piston, was used to apply compression on SKOV-3 ovarian cancer cells in a dynamic and controlled manner by modulating applied gas pressure, localization, shape and size of the micro-piston. We report fabrication of the platform, characterization of the mechanical actuator experimentally and computationally, as well as cell loading and culture in the device. We further show use of the actuator to perform both, repeated dynamic cell compression at physiological pressure levels, and end-point mechanical cell lysis, demonstrating suitability for mechanical stimulation to study the role of compressive forces in cancer microenvironments.

High conductivity and transparency of the electron-transporting layer (ETL) is essential to achieve high efficiency perovskite solar cells (PvSCs). Generally, titanium dioxide (TiO2) has been extensively utilized as an ETL in PvSCs. Both surface roughness and uniformity of the compact-TiO2 (C-TiO2) can influence the efficiency of the PvSC. This work investigates the optimization of the direct current (DC) sputtering power and the ratio of argon (Ar) to oxygen (O2) plasma to achieve high quality ETL films. The effect of changing the DC sputtering power on the C-TiO2 films and subsequently on the overall efficiency was studied. The electrical and optical properties of the C-TiO2 layer were characterized for various DC powers and different ratios of Ar to O2 plasma. It was found that the optimum preparation conditions for the C-TiO2 films were obtained when the DC power was set at 200 W and a flow rate of 6 sccm Ar and 12 sccm O2. A power conversion efficiency (PCE) of 15.3% in forward sweep and 16.7% in reverse sweep were achieved under sunlight simulator of 100 mW/cm2. These results indicate that significant improvement in the efficiency can be achieved, by optimizing the C-TiO2 layer.

In this paper we explore how nano-structure arrays can help improve plasmonic sensors and imaging devices. By using a periodic array the range of parameters that can be varied to give a specific response increases dramatically compared to devices based on individual structures. We show that plasmonic arrays can be engineered to show high quality spectral extinction peaks controlled primarily by the angle of incidence and period with minimal dependence on the structure. This gives flexibility in designing plasmonic sensing or imaging devices. The fabrication of the nanostructure arrays is presented as well as optical verification of the localised plasmon resonance response. Spectral simulation results are also obtained for the arrays using Scattering by Multiple Particles in Thin Film Systems (SMUTHI) software which proves to be a useful tool in analysing the response of plasmonic arrays.

Subradiant surface lattice resonances are of interest due to their remarkably high quality factors. In this work, these high quality resonances are experimentally investigated in the visible spectrum with Au and Ag bipartite disk lattices fabricated with electron beam lithography. Subradiant resonances are also compared to unipartite surface lattice resonance with angle-resolved extinction measurements, which are supported by numerical models. Finally, the lattice parameters are optimized to show high quality factors in lattices where the elements have a diameter difference as small as 10 nm.

Thin film solar cells are one of the important candidates utilized to reduce the cost of photovoltaic production by minimizing the usage of active materials. However, low light absorption due to low absorption coefficient and/or insufficient active layer thickness can limit the performance of thin film solar cells. Increasing the absorption of light that can be converted into electrical current in thin film solar cells is crucial for enhancing the overall efficiency and in reducing the cost. Therefore, light trapping strategies play a significant role in achieving this goal. The main objectives of light trapping techniques are to decrease incident light reflection, increase the light absorption, and modify the optical response of the device for use in different applications. Nanostructures utilize key sets of approaches to achieve these objectives, including gradual refractive index matching, and coupling incident light into guided modes and localized plasmon resonances, as well as surface plasmon polariton modes. In this review, we discuss some of the recent developments in the design and implementation of nanostructures for light trapping in solar cells. These include the development of solar cells containing photonic and plasmonic nanostructures. The distinct benefits and challenges of these schemes are also explained and discussed.

In this paper, we demonstrate that periodic inverted nanopyramid structures can enhance the power conversion efficiency of monocrystalline silicon solar cells by minimizing reflections, improving light trapping process in addition to its self-cleaning functionality. The periodic inverted nanopyramid structures were fabricated on monocrystalline silicon solar cell surfaces using a UV nanoimprint lithography. By introducing inverted nanopyramid structures on the front side of the monocrystalline silicon solar cells, the power conversion efficiency was improved by 11.73% compared to identical solar cells without the texturing. The inverted nanopyramid coating decreased the reflectance and increased the external quantum efficiency over a broad wavelength range. Moreover, the surface of the solar cells exhibited hydrophobic properties due to increased contact angle caused by the nanostructure patterns and the self-assembled monolayer coating. The enhanced hydrophobicity provided the solar cells with an added self-cleaning functionality. These results suggest that the periodic inverted nanopyramid structures has high potential in improving the performance of silicon solar cells and may be applied to different types of solar cells.

In this work, indium tin oxide (ITO) thin films were grown on a glass substrate without introducing oxygen into the growth environment using RF magnetron sputtering technique. The dependence of surface morphological, optical and electrical properties at different film thicknesses and sputtering RF power were investigated. Results showed that these properties were strongly influenced by the film thickness and sputtering RF power. It was found that the resistivity, sheet resistance and optical transmittance of ITO thin films deposited on glass substrate decreased as film thickness increased from 75 to 225 nm while the surface roughness and optical bandgap increased. The optimum properties were obtained for ITO films 225 nm thick grown at 250 W RF power. This has revealed an excellent figure of merit of (38.4 × 10−4 Ω−1) with average transmittance (83.3 %), resistivity (9.4 × 10−4 Ω cm), and carrier concentration (6.1 × 1020 cm−3). These ITO films are suitable for use in solar cells applications.

Cells are cultured on platforms made of a variety of materials with selected topographies during studies of cell response and behavior. Understanding the effects of substrates is essential for such applications as developing effective interfaces between body cells and implanted materials and devices. In this study, the effects of substrate surface properties on cell differentiation and alignment on C2C12 myoblasts cultured on conventional or fabricated polymeric cell culture substrates were investigated. Comparisons were made between cells cultured on tissue culture grade polystyrene (TCPS), glass, Permanox, and cured polydimethylsiloxane (PDMS) substrates. Fluorescent immunohistochemistry of cell markers was used to analyse the extent of differentiation. Alignment and guidance of cell growth and spread were studied using patterned platforms. Gratings were made on polystyrene (PS) and PDMS and differentiation was facilitated after 5 days by media exchange. Differences in cell morphology were observed between cells cultured on TCPS and PDMS substrates. Fully differentiated myotubes were observed in highest numbers on TCPS substrates and were non-detectable on PDMS substrates in the time frame of 144 h. Muscle cell alignment and their differentiation followed along the grating patterns on PS and elongated along the pattern length. On the other hand, on PDMS cells formed sheets of tissue and peeled from the substrate. We have revealed the potential for the combinations of surface materials and topography on cell behavior to induce accelerated differentiation and coordinated alignment. The results demonstrate that culture environment can be designed or engineered to modify or regulate muscle cell functions. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 1638-1645, 2016.

The importance of the biophysical cellular environment in cancer development has been increasingly recognised but so far has been only superficially studied. Here we investigated the effect of cell-like substrate topography on ovarian cancer cell behaviour and potential underlying signalling pathways. We observed changes in cell morphology in response to substrate topography, which implies modification of structure-function associations. Differences in focal adhesion signalling and Rho/ROCK activity suggested their involvement in the biomechanically-driven cellular responses. Cell-like topography was also shown to modulate the MAPK pathway and hence potentially regulate cell proliferation. The selective regulation of the cells by the mechanotransduction pathways that we noted has wide ranging implications for understanding cancer development. We established that the physical architecture of cell culture substrate is sufficient to influence cancer cell behaviour, independent of genetic composition or biochemical milieu.

Direct writing is an effective and versatile technique for three-dimensional (3D) fabrication of conducting polymer (CP) structures. It is precisely localized and highly controllable, thus providing great opportunities for incorporating CPs into microelectronic array devices. Herein we demonstrate 3D writing and characterization of poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) pillars in an array format, by using an in-house-constructed variant of scanning ion conductance microscopy (SICM). CP pillars with different aspect ratios were successfully fabricated by optimizing the writing parameters: pulling speed, pulling time, concentration of the polymer solution, and the micropipette tip diameter. Especially, super high aspect ratio pillars of around 7 μm in diameter and 5000 μm in height were fabricated, indicating a good capability of this direct writing technique. Additions of an organic solvent and a cross-linking agent contribute to a significantly enhanced water stability of the pillars, critical if the arrays were to be used in biologically relevant applications. Surface morphologies and structural analysis of CP pillars were characterized by scanning electron microscopy and Raman spectroscopy, respectively. Electrochemical properties of the individual pillars of different heights were examined by cyclic voltammetry using a double-barrel micropipette as an electrochemical cell. Exceptional mechanical properties of the pillars, such as high flexibility and robustness, were observed when bent by applying a force. The 3D pillar arrays are expected to provide versatile substrates for functionalized and integrated biological sensing and electrically addressable array devices.

Microelectrode geometry has significant influence on particles trapping techniques used on bioanalysis platforms. In this paper, the particle trapping patterns of dipole, quadrupole and octupole microelectrode using dielectrophoretic force (DEP) are discussed. The microelectrodes were constructed on a metal-insulator-metal platform, built on a silicon nitride (Si3N4) coated silicon substrate. The back contact is made from 20 nm nickel-chromium (NiCr) and 100 nm gold (Au) as the first layer. Then, SU-8-2005 (negative photoresist) is used on the second layer to create microcavities for trapping the particles. The third layer, where the three geometries were patterned, is made from 20 nm NiCr and 100 nm Au layers. Prior to fabrication, the particles trapping patterns of the microelectrodes were profiled using a finite element software, COMSOL 3.5a. Trapping patterns for the three geometries were evaluated using polystyrene latex microbeads. Results from the experiment validate simulation studies in term of microelectrode trapping ability up to single particle efficiency. It provides the potential of converting the trapping platform into a lab-on-chip system.

Display Omitted Inverted nanopyramids were fabricated by interference lithography and KOH etching.The reflectivity of inverted nanopyramids below 10% over visible region.A 67% increase in efficiency was achieved by nanopyramid texturing. We report on a maskless and scalable technique for fabricating nano-scale inverted pyramid structures suitable for light management in crystalline silicon solar cells. This technique utilizes interference lithography and subsequent combined dry and KOH wet pattern transfer etching techniques. The inverted nanopyramid structures suppress the total reflection at normal incidence to below 10% over the entire visible range. The overall efficiency of the solar cell has been increased by 67% with the inverted nanopyramid texturing. The standard dual MgF2/ZnS anti-reflection coating further enhanced the overall efficiency by 5.79%.

Patterned nanoscale molecular films will be a key componentof advanced devices such as novel chemical and biologicalsensors and nanoelectronic systems. For long-establishedsurface modification strategies such as the use of self-assembledmonolayers ofalkanethiolsat noblemetal surfacesandreactionsofsilanesatoxidesurfaces,patterningstrategieshave reached a high level of sophistication.

Topographical features of cells at nanometre resolution were fabricated in polystyrene. The study investigated the effect of physical topography on the response of cancer cells to the common anticancer drugs, paclitaxel and doxorubicin. Human endometrial cancer cells (Ishikawa) were incubated on substrates containing cell-like features that had been fabricated using our bioimprint methodology to create moulds of cells with positive (convex) and negative (concave) topography. Control cultures were performed on flat substrates. Effects of the drugs on caspase-3 expression, proliferating nuclear antigen (PCNA) expression, cell number and vascular endothelial growth factor (VEGF) secretion were determined. Results revealed that the topography influenced the cell responses in a drug-dependent manner i.e. paclitaxel effects were sensitive to topography differently to those of doxorubicin. In addition, function signalling pathways were sensitive to the detailed topography i.e. positive imprint and negative imprint induced distinct response patterns. The results in this study show for the first time that a culture surface with cell-like topography, that has both nano- and micro-resolution, influences endometrial cancer cell responses to chemotherapy drugs. The effects are dependent on the topography and also on the chemotherapy drug. In particular, the platforms described have potential to provide substrates with high physical relevancy on which to undertake preclinical testing of new drugs. The method also allows for use of different cell types to provide cell-specific topography. The results imply that physical architecture of the cancer cell environment may be a suitable prospective target to enhance clinical activity of traditional drugs. Additionally or alternatively we provide compelling support for the notion that understanding the physical component of the nano- and micro-environment may encourage a redirection of drug development. Further, our observation that the cells distinguish between the different cell-like topographies (positive and negative bioimprints) indicates that a realistic topography is advantageous as growth platforms in experiment design.

In this paper, we report on the integration of a force measurement application capable of continuously measuring the forces generated by C. elegans in motion with a series of controllable microvalves which have an additional ability to increase control over worm selection and manipulation. The three-layer device consists of a pneumatic layer at the top, and a fluidic layer at the bottom with a thin PDMS membrane which functions as a microvalve sandwiched in between. The pneumatic layer functions as valves, whose operation is controlled pneumatically. The fluidic layer contains of PDMS micropillars for resolving the worm force from the deflection of the cantilever-like pillars. The measured force is horizontal and equivalent to a point force acting at half of the pillar height. By carefully controlling the incorporated microvalves, the proposed device is able to select and direct worm movement and at the same time increase the number of force measurement results collected. The integration of the microvalve...

The periodic inverted nanopyramid structures were fabricated on monocrystalline and polycrystalline silicon solar cell surface respectively. This was achieved by utilizing a UV nanoimprint stamp with an upright nanopyramid structures made on UV curable resist coated glass substrate. The reflectance of both solar cells was significantly decreased over a broad wavelength range and the total conversion efficiency of monocrystalline and polycrystalline Si solar cells was increased by 11.73% and 6.87% compared to the identical solar cell without the inverted nanopyramid structure respectively. This low-cost fabrication method of nanostructures is suitable for applications in different types of solar cells.

This paper introduces a new quadrupole microelectrode design for trapping mass loading of single cells using dielectrophoretic (DEP) force. The DEP force profiles generated by the pattern which represent trapping regions on the biochip platform, were studied using finite element software Comsol Multiphysics v3.5a. Arrays of the quadrupole microelectrode were patterned on a multilayer structure called sandwiched insulator with back contact (SIBC) biochip platform, fabricated using photolithography technique. This platform consists of a 10nm Nickel-Chromium (NiCr) and 100nm Gold (Au) top electrode, [email protected] thick SU-8 2005 insulation layer and a bottom layer of 10nm NiCr and 100nm Au called the back contact. Access to the back contact is achieved via a microcavity located at the center of the quadrupole microelectrode arrangement. Together, the DEP forces generated from the quadrupole microelectrode and the microcavities are used to anchor single cells and maintain cell positions. The quadrupole design was tested with polystyrene latex microbeads, and Ishikawa cancer cells suspended in media and flowed through microfluidic channels made from PDMS. Single cell trapping becomes evident when both quadrupole microelectrode and back contact are biased using AC potentials of different phases. Experiment results show that the quadrupole microelectrode trapped 22 percent of Ishikawa cancer cells and 17 percent of the polystyrene microbeads.

The influence of the processing parameters on conformality is studied for pulsed-pressure (PP) metal-organic (MO)CVD. A statistical method to measure conformality, and a model for pulse vapor exposure are presented. Titanium dioxide (TiO2) thin films are deposited from a liquid titanium isopropoxide (TTIP, Ti(OPr)4) solution with no carrier gas on silicon and silicon nitride substrates with 3-D micrometer- and nanometer-scale structures. The deposited films are columnar anatase TiO2 with thicknesses between 130 nm and 310 nm, controlled by the number of pulses. The statistical conformality varies from 0.81 to 0.93, decreased slightly with increasing deposition temperature, and is insensitive to pulse exposure.

With a reduced set of 300 neurons and a fully sequenced genome, the multicellular nematodeCaenorhabditis eleganshas recently gained increasing interest as a model organism for neurobiological studies. One particular area of interest is related to worm locomotion and the investigation of the correlation between individual genes, neurons, muscle arms and the motion pattern of the nematodes. To characterize motion patterns of movingC. eleganswe have previously demonstrated an automated force measurement setup using microfabricated polydimethylsiloxane (PDMS) pillars and image processing. In this paper we introduce an integrated microfluidic device for worm sorting and force measurement. The device allows for high-throughput measurements by combining sorting functions on-chip with the existing force pattern measurement system. A horizontal sorting channel and branching vertical pillar array channels are utilized for worm sorting. Using the former, the nematodes can be flow-directed into arrays of 40 µm and 60 µm diameter pillars based on worm size and type. This improves animal survival and increases the relevance of the force measurement by allowing one to match the amplitude of the worm movement to the pillar spacing. The PDMS based device consists of three layers: a fluidic layer with pillars for force measurement at the bottom, a gas layer on top and a thin PDMS layer sandwiched between them. By applying pressure to the gas layer, the membrane in the middle will be deflected thus restricting the worms’ movement in the fluidic channel.

Recent advances in medical sciences have revealed the significance of cellular structures and morphology in biological function. A cell's membrane represents the boundary between the cells and its environment. The variations in cell surface and morphologies may be used as indications of malfunction or even diseases. If abnormalities such as cancer can be detected at the molecular level this will offer an important means for early diagnosis using small numbers of cells. The use of electron and scanning probe microscopy such as atomic force microscopy (AFM) could facilitates the opportunity to study and examine the molecular processes of living cells in greater details. The difficulties faced in direct cellular analysis when using and operating the AFM in situ for morphological studies of the cells has led to the development of a novel approach called Bioimprint (Traut and Papanicolaou, 1941 [1]). Inspired by the high resolution of nanoimprint lithography processes, Bioimprint has been applied to a new area of biological cell replication for the purpose of imaging and analysis and has revealed some very important biological events when combined with AFM imaging. For this research, the structural features of endometrial cancer cells were investigated. Regulation of selected peptides were examined, especially those which are associated with angiogenic factors that promote the proliferation of nutrient-bearing blood vessels that support tumour growth. Using the Bioimprint technique which is a soft lithography process, an impression of the cell topology was created by applying a layer of monomer mixture onto the cells attached to a substrate and rapidly curing it under UV-light. Fast UV-radiation enables the imprint to lock cellular processes within minutes and replicas of the cancer cells exhibit structures down to nanometer scale. Cancer cells were cultured and incubated in accordance with standard biological culturing procedures and protocols approved by the New Zealand Human Ethics Committee. High-resolution AFM imagery provides the opportunity to examine the structure and topography of the cells closely so that any abnormalities can be identified. To study the replicated imprints, the features that resembled secretory pores on the AFM images were noted. The numbers of pores correlated well with levels of vascular endothelial growth factor (VEGF) that were secreted by the cells. Further experiments were conducted in which anti-VEGF-coated microbeads were observed in the AFM images to be attracted to the areas of the pores.

We report the development and characterization of a microfluidics-based bioimprint process using high-density microchannel arrays for cell-culture and polymer delivery. The tubeless PDMS arrays consist of multiple independent microchannels and allow for parallelized bioimprint via automated dispensing and passive pumping. Using the microchannels, a 400nm thin test pattern was replicated into a methacrylate biopolymer to demonstrate process applicability. Bioimprints of cobalt chloride stimulated Ishikawa endometrial cancer cells exhibiting exocytosis-like pore structures were compared with controls using AFM to exemplify a process application. The devices can be used for high-throughput cell assays, cell developmental studies and the formation of phenotype-specific biomimetic scaffolds.

Dye Sensitized Solar Cells (DSSC) possess huge potential in solar energy utilisation. Immense research has been carried out in order to improve its performance. This paper suggests an alternative way of employing Light Trapping technique on DSSC by dry etching substrates before depositing the transparent conductive oxide (TCO) layer on one of the electrodes. The result demonstrated a decrease in reflectance before depositing the TCO, but an increase in reflectance after depositing the TCO. Texturing might also help to increase the effective surface area at the interface between various cell layers, providing a shorter path for the electron transport layer and improving collection efficiencies.

Replication of biological cells for the purpose of imaging and analysis under electron and scanning probe microscopy has facilitated the opportunity to study and examine some molecular processes of living cells in a manner that was not possible before. The difficulties faced in direct cellular analysis when using and operating atomic force microscopy (AFM) in situ for morphological studies of biological cells has lead to the development of a novel method for biological cell studies based on nanoimprint lithography. The realisation of the full potential of high-resolution AFM imaging has revealed some very important biological events such as exocytosis and endocytosis. In this work, a soft lithography bioimprint replication technique, which involved simple fabrication steps, was used to form a hard replica of the cell employing a newly developed biocompatible polymer that has fast curing time at room temperature essential for this process. The structure and topography of the endometrial (Ishikawa) cancer cell was investigated in this study. Cells were cultured and incubated in accordance with standard biological culturing procedures and protocols approved by the Human Ethics Committee, University of Otago. An impression of the cell profile was created by applying a layer of the polymer onto the cells attached to a substrate and rapidly cured under UV-light. Fast UV radiation helps to lock cellular processes within minutes after exposure and replicas of the cancer cells exhibit ultra-cellular structures and features down to nanometer scale. Elimination of the AFM tip damping effects due to probing of the soft biological tissue allows imaging with unprecedented resolution. High-resolution AFM imagery provides the opportunity to examine the structure and topography of the cells closely so that any abnormalities can be identified. Craters that resemble granules may be observed. These represent steps on a transitional series of sequential structures that indicate either an endocytotic or exocytotic processes, which were evident on the replicas. These events, together with exocytosis, play a very significant part in the tumorigenesis of these cancer cells. By forming cell replica impressions, not only have they the potential to understand biological cell conditions, but may also benefit in synthesizing three dimensional (3-D) scaffolds for natural growth of biological cells and provide an improvement over standard cell growth conditions.

This paper describes a single-step pattern transfer process for three-dimensional (3D) structures onto quartz substrates. The 3D patterns were defined on a negative resist (ma-N2403) using variable controlled acceleration voltage in the electron beam lithography (EBL) process. The developed 3D patterns on the negative resist were utilized as the masking layer and later transferred onto quartz substrate by employing fluorinated plasma etching process. The etching chemistry of CHF"3 plasma on both 3D masking layer and quartz substrate was analysed to guide etching process optimization. The 3D etching mechanism was also analysed to help in achieving the desired final 3D pattern profiles for imprint process. The causes of surface roughness formation were analysed and appropriate remedies were suggested. The Oxford Plasmalab 80plus etcher was employed for transferring the 3D patterns on quartz substrate using a gas mixture of CHF"3/Ar with a ratio of 9.0/6.25sccm, etching pressure of 5mTorr, RF power of 125W and at room temperature. This setting was found to achieve a 10nm/min etch rate, better control of 3D profiles and surface roughness of less than 2nm.

Pattern writing on insulating materials (e.g. quartz) using electron beam lithography (EBL) is a challenging task and it is even more difficult when the pattern is three dimensional (3D). Surface charging trapped on insulating substrates may deflect the electron beam during electron beam pattern writing causing undesired effects. In this work, the surface charging has been suppressed by top coating with water soluble conductive polymer layer using poly (3,4-Etylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS). The 3D masking profiles are created on a negative tone photoresist (Microresist, ma-N2403) using Raith150 EBL tool with variable dose controlled beam exposure. The 3D patterns have been transferred onto the quartz substrate by single step reactive ion etching (RIE) with suitable resist to substrate selectivity. We have demonstrated the fabrication of 3D geometrical shapes such as pyramids, hemispheres, and cones with dimensions down to 300nm using this technique without any surface charging effects.

The study investigates the use of ultraviolet nanoimprint lithography (UV-NIL) for patterning three dimensional (3D) structures. Generating the 3D structures is a challenging task especially on an insulating substrate such as quartz. These transparent molds are essential for the UV-NIL process. The 3D profiles were created on the negative tone photoresist, Microresist ma-N2403 using a Raith150 electron beam lithography (EBL) tool in a single step variable dose controlled exposure. The developed 3D resist profiles subsequently were utilized as the 3D masking layer. The 3D patterns were transferred into the quartz mold substrates by a single-step reactive ion etching (RIE). The replication of the 3D mold structure by using the UV-NIL technique requires a two-step imprint process. The master mold profile was replicated onto a Microresist Ormocomp US-S4 resist on the first imprint to become the soft mold. The cured Ormocomp soft mold, subsequently was used as a mold for replicating the 3D pattern structures o...

Thin titania (TiO2) films were deposited on patterned silicon (Si), and silicon nitride (SiN) substrates by pulsed-pressure metal organic chemical vapor deposition (PP-MOCVD) using titanium tetra-isopropoxide (TTIP) as a precursor. The deposition temperature was varied between 400 °C and 600 °C under peak pressure of up to 370 Pa. The surface morphology and thicknesses of the films were examined using a scanning electron microscope (SEM). X-ray diffraction (XRD) was used to analyze the phases of TiO2. The thicknesses of TiO2 films were in the range of 200–350 nm. The phase of thin TiO2 at the deposition temperatures was anatase, exhibiting slight reduction in grain size with increasing temperature. The composition of the films was qualitatively identified by energy dispersive X-ray spectroscopy (EDS). The principal composition of the thin films was TiO2. The conformality of TiO2 films on features was evaluated based on statistical analysis. The step coverage of TiO2 at low temperatures showed a good even coating with a growth rate of more than 20 nm/min. As the temperature increased, the evenness of the coating along a micron-scale step decreased.

Zinc oxide (ZnO) thin films were deposited on various substrates by DC sputtering deposition. Thermal annealing was performed at up to 1,200°C in N2 for 30 min. The effect was investigated using x-ray diffraction (XRD), photoluminescence (PL) spectra, scanning electron microscopy (SEM), and piezoresponse force microscopy (PFM). The influence on PL response depends both on substrate material and annealing temperature. The PFM images reveal that the ZnO films have inversion domains. While annealing improves the piezoresponse, the inversion domains still persist. The cross-sectional analysis of the inversion domains shows domain boundary widths of approximately 1.5 nm.

Li Hui Tan,1,2 Peter H Sykes,1 Maan M Alkaisi,2,3 John J Evans1,2,4 1Department of Obstetrics and Gynaecology, University of Otago, Christchurch, 2MacDiarmid Institute for Advanced Materials and Nanotechnology, Wellington, 3Department of Electrical and Computer Engineering, University of Canterbury, Christchurch, 4Centre for Neuroendocrinology, University of Otago, Christchurch, New Zealand Abstract: Conventional in vitro culture studies on flat surfaces do not reproduce tissue environments, which have inherent topographical mechanical signals. To understand the impact of these mechanical signals better, we use a cell imprinting technique to replicate cell features onto hard polymer culture surfaces as an alternative platform for investigating biomechanical effects on cells; the high-resolution replication of cells offers the micro- and nanotopography experienced in typical cell–cell interactions. We call this platform a Bioimprint. Cells of an endometrial adenocarcinoma cell line, Ishikawa, were cultured on a bioimprinted substrate, in which Ishikawa cells were replicated on polymethacrylate (pMA) and polystyrene (pST), and compared to cells cultured on flat surfaces. Characteristics of cells, incorporating morphology and cell responses, including expression of adhesion-associated molecules and cell proliferation, were studied. In this project, we fabricated two different topographies for the cells to grow on: a negative imprint that creates cell-shaped hollows and a positive imprint that recreates the raised surface topography of a cell layer. We used two different substrate materials, pMA and pST. We observed that cells on imprinted substrates of both polymers, compared to cells on flat surfaces, exhibited higher expression of β1-integrin, focal adhesion kinase, and cytokeratin-18. Compared to cells on flat surfaces, cells were larger on imprinted pMA and more in number, whereas on pST-imprinted surfaces, cells were smaller and fewer than those on a flat pST surface. This method, which provided substrates in vitro with cell-like features, enabled the study of effects of topographies that are similar to those experienced by cells invivo. The observations establish that such a physical environment has an effect on cancer cell behavior independent of the characteristics of the substrate. The results support the concept that the physical topography of a cell’s environment may modulate crucial oncological signaling pathways; this suggests the possibility of cancer therapies that target pathways associated with the response to mechanical stimuli. Keywords: surface characteristics, cell culture platforms, physical microenvironment, cell response, drug targets, mechanical forces

Replication and fixation techniques have been of considerable interest for imaging and analysis of biological cells since the introduction of electron and scanning probe microscopy. Although such tools as the atomic force microscope (AFM) permit in situ morphological studies at a magnitude of resolution beyond traditional optical microscopy, they are difficult to operate and their resolution capabilities are rarely realized. We used a UV-Bioimprint replication technique to imprint a polymer layer onto cells attached to a substrate and rapidly cure to create an impression of cell topography. Replicas of chemically fixed and untreated cells analyzed by atomic force microscopy demonstrate nanometer resolution in the transfer of replicated features. UV-Bioimprint presents an improvement over techniques using heat-curable polymers as well as an alternative technique to the direct imaging of cells. The motivation for UV-Bioimprint is to effectively integrate scanning probe microscopy tools for imaging of cellular ultrastructure.