Micropatterning Technique Research Articles

Biosensing using photolithographically micropatterned electrodes of PEDOT:PSS on ITO substrates

Improving the performance of electrochemical sensors based on indium tin oxide (ITO) can be achieved via intrinsically conducting polymers such as poly (3, 4 ethylenedioxythiophene): polystyrene sulfonate (PEDOT:PSS). However micropatterning of PEDOT:PSS to form microelectrodes on such substrates has been challenging. Here we demonstrate a technique for the precise micropatterning of a conductive ink on ITO using photolithography to realize a covalently-attached ion-transport matrix for stable biosensing. This micropatterning is accomplished using an all water-based and ambient temperature processing. We present electrochemical characterization of the material composite via electrochemical impedance spectroscopy, cyclic voltammetry and differential pulse voltammetry. A sensitive sensor is fabricated for the neurotransmitter dopamine, with a linear range from 1 to 50μM. The sensor signal is very stable under cyclic increase and decrease in the concentration of dopamine. This sensing can be achieved even in the presence of ascorbic acid at 1000 times higher concentration than dopamine. Further, enzymes can be immobilized in the conductive matrix to form highly selective sensors. Such robust micropatterning strategies can greatly expand the use of conducting polymer substrates in biosensing applications.

(Invited) All-Carbon Integrated Circuits for Flexible/Stretchable Electronics

Flexible and stretchable electronics are attracting much attention because of the variety of potential applications from flexible e-papers though wearable healthcare devices. Among various kinds of electronic materials, carbon nanotube thin films have advantages in flexibility, stretchability, and performance because of the excellent electronic and mechanical properties. Low cost manufacturing is also possible with printing techniques due to the good processability of carbon nanotube films. In the presentation, I will talk about our recent works on flexible and stretchable devices based on carbon nanotube thin films for realizing wearable healthcare electronics, including high-mobility all-carbon thin-film transistors and integrated circuits fabricated on a plastic or PDMS film. The simple fabrication processes based on micro-patterning technique of CNT films and high-throughput printing techniques will also be presented. First, we have developed a method to realize high-mobility CNT thin films, based on a gas-phase filtration and transfer process. CNTs were grown by a floating-catalyst CVD technique. The CNT network was collected by filtering through membrane filters at room temperature. The CNT network was transferred from a membrane filter to the substrate with electrodes of TFTs. This technique enables to form CNT films with high mobility and controllable threshold voltage on a plastic film. A TFT fabricated on a Si substrate with the transfer technique exhibited a high mobility of 634 cm2/Vs with on/off ratio of 6x106. Various integrated circuits such as basic logic gates, ring oscillators, and flip-flops were demonstrated on a transparent plastic film. The operation speed of the present IC was evaluated with the ring oscillator to be 12 μs/gate. Since the delay time is dominated by the parasitic capacitances of overlap regions of the source-gate and drain-gate electrodes, there is a room to improve the operation speed. By modifying the device structure to eliminate the overlap capacitance, the gate delay was improved to be 2.3 μs/gate. CNT films can also be used as electrodes and interconnections, which are flexible, transparent, stable, and free of rare metals. By using CNT transparent conductive films, we realized all-carbon TFTs and ICs, in which the electrodes and interconnections consist of CNT film and the insulators consist of PMMA. All carbon ICs were operated at relatively low voltage of 5 V even for the thick polymer gate insulator. The all-carbon devices exhibit unique moldability, which is important property of plastic materials to produce plastic products from toys through electronics devices and medical devices. We demonstrated three-dimensional dome-shape devices formed by the thermo-pressure forming technique, in which devices were stretched bi-axially by up to 18%. We also fabricated stretchable and transparent all-carbon transistors on PDMS substrates. One-dimensional tensile strain test showed a small degradation in drain current as 8 % under the tensile strain of 20%. We also confirmed that the device worked even for 40% tensile strain, and the drain current returned to the initial value when the strain was released. Printing process is also attractive to fabricate devices on a plastic film at low cost. We have introduced high-throughput flexographic printing technique, which is a kind of high-speed typographic printing technique with a flexible relief plate made of photopolymer, in the fabrication process of CNT TFT. Bottom-gate-type CNT TFTs were fabricated by fully lithography-free and nonvacuum process on a PEN film.

Improved conductivity and capacitance of interdigital carbon microelectrodes through integration with carbon nanotubes for micro-supercapacitors

In the last decade, pyrolyzed-carbon-based composites have attracted much attention for their applications in micro-supercapacitors. Although various methods have been investigated to improve the performance of pyrolyzed carbons, such as conductivity, energy storage density and cycling performance, effective methods for the integration and mass-production of pyrolyzed-carbon-based composites on a large scale are lacking. Here, we report the development of an optimized photolithographic technique for the fine micropatterning of photoresist/chitosan-coated carbon nanotube (CHIT-CNT) composite. After subsequent pyrolysis, the fabricated carbon/CHIT-CNT microelectrode-based micro-supercapacitor has a high capacitance (6.09 mF·cm–2) and energy density (4.5 mWh·cm–3) at a scan rate of 10 mV·s–1. Additionally, the micro-supercapacitor has a remarkable long-term cyclability, with 99.9% capacitance retention after 10,000 cyclic voltammetry cycles. This design and microfabrication process allow the application of carbon microelectromechanical system (C-MEMS)-based micro-supercapacitors due to their high potential for enhancing the mechanical and electrochemical performance of micro-supercapacitors.

Cell shape and the presentation of adhesion ligands guide smooth muscle myogenesis.

The reliable generation of smooth muscle cells is important for a number of tissue engineering applications. Human mesenchymal stem cells (MSCs) are a promising progenitor of smooth muscle, with high expression of smooth muscle markers observed in a fraction of isolated cells, which can be increased by introduction of soluble supplements that direct differentiation. Here we demonstrate a new micropatterning technique, where peptides of different ligand affinity can be microcontact printed onto an inert background, to explore MSC differentiation to smooth muscle through controlled biochemical and biophysical cues alone. Using copper-catalyzed alkyne-azide cycloaddition (CuAAC), we patterned our surfaces with RGD peptide ligands-both a linear peptide with low integrin affinity and a cyclic version with high integrin affinity-for the culture of MSCs in shapes with various aspect ratios. At low aspect ratio, ligand affinity is a prime determinant for smooth muscle differentiation, while at high aspect ratio, ligand affinity has less of an effect. Pathway analysis reveals a role for focal adhesion turnover, Rac1, RhoA/ROCK, and calpain during smooth muscle differentiation of MSCs in response to cell shape and the affinity of the cell adhesion interface. Controlling integrin-ligand affinity at the biomaterials interface is important for mediating adhesion but may also prove useful for directing smooth muscle myogenesis. Peptide patterning enables the systematic investigation of single to multiple peptides derived from any protein, at different densities across a biomaterials surface, which has the potential to direct multiple MSC differentiation outcomes without the need for soluble supplements.

Analysis of Receptor Tyrosine Kinase and G-Protein Coupled Receptor Signaling Dynamics on Micro-Structured Surfaces

Membrane-localized proteins are essential to transmit signals into the cell. An important issue is the interaction of these proteins with cytosolic proteins. To quantify such often short-lived interactions we have introduced a method based on the combination of micro-structured surfaces and TIRF microscopy.(1,2) We have used the assay to validate the efficacy of medically relevant receptor tyrosine kinase (RTK) modulators.(3) Bait epidermal growth factor (EGF) receptor molecules were forced into microscopic domains, while monitoring co-recruitment of fluorescent intracellular prey Grb2 molecules. Pretreatment with pharmacologically active ingredients used for the treatment of human cancers significantly reduced this interaction. A similar approach was used for the quantitative analysis of the interaction between different insulin receptor substrate (IRS) proteins and the insulin/IGF-I receptor.(4) The micro-patterning technique enabled the measurement of equilibrium associations and interaction dynamics of these molecules with high specificity. We revealed that several domains of IRS critically determine the turnover rate of the receptors. Furthermore, we found significant differences among IRS proteins in the strength and kinetic stability of the interaction with the receptors, which could account for the diverse IRS functions. Finally, we studied the interaction of the GPCR s2-adrenoceptor (s2AR) with arrestin-3.(5) By measuring arrestin-3 recruitment and the stability of arrestin-3-receptor complexes in real time using FRAP analysis on micro-patterned surfaces, we could demonstrate that arrestin-3 dissociates quickly and almost completely from the β2AR. Recently, we have implemented micro-structured and functionalized multi-well plates. This development step sets a milestone in terms of throughput rates of our methodology.

Micro-patterning technique using a rotating cutting tool controlled by an electromagnetic actuator

This work describes a micro-patterning or surface texturing technique on the fixed work surface using a proposed new spindle system with a rotating cutting tool controlled in real time. The proposed spindle system creates micro-sized patterns using rotating tools such as a micro-milling tool and a micro-grinding wheel. The shaft of the spindle is suspended by air bearings, and an electromagnetic actuator controls the radial motion of the spindle housing instead of the shaft. This generates a micro-pattern array on the electro-less Ni-coated workpiece in the micro-milling process. A PID controller is adopted to make the system stable, and adaptive feedforward cancellation is used to effectively compensate for the run-out of the spindle system during machining. The machining results show that this compensation improves the pattern accuracy. It is expected that micro-patterning using the proposed spindle system can be applied over a large surface area.

Laser Direct Write micro-fabrication of large area electronics on flexible substrates

To date, Laser Direct Write (LDW) techniques, such as Laser Induced Forward Transfer (LIFT), selective laser ablation and selective laser sintering of metal nanoparticle (NP) ink layers are receiving growing attention for the printing of uniform and well-defined conductive patterns with resolution down to 10μm. For flexible substrates in particular, selective laser sintering of such NP patterns has been widely applied, as a low temperature and high resolution process compatible with large area electronics. In this work, LDW of silver NP inks has been carried out on polyethylene-terephthalate (PET), polyethylene-naphthalate (PEN) and polyimide (PI) substrates to achieve low electrical resistivity electrodes. In more detail, high speed short pulsed (picosecond and nanosecond) lasers with repetition rates up to 1MHz were used to print (LIFT) metal NP inks. We thus achieved uniform and continuous patterns with a minimum feature size of 1μm and a total footprint larger than 1cm2. Next, the printed patterns were laser sintered with ns pulses at 532nm over a wide laser fluence window, resulting in an electrical resistivity of 10μΩcm. We carried out spatial beam shaping experiments to achieve a top-hat laser intensity profile and employed selective laser ablation of thin films (thickness on the order of 100nm) to produce silver micro-electrodes with a resolution on the order of 10μm and a low line edge roughness. Laser sintering was combined with laser ablation to constitute a fully autonomous micro-patterning technique of metallic micro-features, with a 10μm resolution and geometrical characteristics tuned for interdigitated electrodes for sensor applications.

Hydrogel-free alternate soaking technique for micropatterning of bioactive ceramics on wettability-patterned substrates around room temperature

Abstract We discuss a hydrogel-free alternate soaking technique for the micropatterning of bioactive ceramics on wettability-patterned substrates around room temperature. Wettability-patterned substrates were fabricated by partly removing self-assembled monolayers on glass plates using mask exposure of UV–Ozone. Hydroxyapatite scaffolds or calcium carbonate films were formed selectively on the hydrophilic surface of the wettability-patterned substrates by alternate soaking of the wettability-patterned substrates in two kinds of calcifying solutions. The wettability-patterned substrates formed with hydroxyapatite scaffolds were immersed in hydroxyapatite precursor for the growth of hydroxyapatite crystals. The c plates of hydroxyapatite crystals were highly aligned parallel to the substrates in the initial stage. This technique allow for the micropatterning of bioactive ceramics with low cost, low energy and short time because this technique does not require bioactive glasses which require calcination process for activation, or hydrogels which need long diffusion time of hydroxyapatite precursor, contributing to the application to templates for bio-living culture cells and cell arrays for medical diagnosis with environmentally-friendly fabrication process in the future.

Fabrication of Micro Single Chamber Solid Oxide Fuel Cell Using Photolithography and Pulsed Laser Deposition

This paper focuses on the fabrication of micro-coplanar interdigitated single chamber solid oxide fuel cell (μ-SC-SOFC) using a combination of micropatterning technique and thin-film deposition technology. Photolithography was used to generate the micro-interdigitated photoresist patterns on the substrates. Pulsed laser deposition (PLD) method was used to deposit thin films of microstructured electrolytes yttrium stabilized zirconia (YSZ) and electrodes (anode: YSZ + NiO and cathode: lanthanum strontium ferrous cobalt (LSCF)). Process parameters were optimized to obtain consistent functional microstructure and crystal morphology. This research shows good potential for combinatorial manufacturing methods to fabricate high quality and repeatable micro fuel cell components.

Microcontact peeling as a new method for cell micropatterning.

Micropatterning is becoming a powerful tool for studying morphogenetic and differentiation processes of cells. Here we describe a new micropatterning technique, which we refer to as microcontact peeling. Polydimethylsiloxane (PDMS) substrates were treated with oxygen plasma, and the resulting hydrophilic layer of the surface was locally peeled off through direct contact with a peeling stamp made of aluminum, copper, or silicon. A hydrophobic layer of PDMS could be selectively exposed only at the places of the physical contact as revealed by water contact angle measurements and angle-resolved X-ray photoelectron spectroscopy, which thus enabled successful micropatterning of cells with micro-featured peeling stamps. This new micropatterning technique needs no procedure for directly adsorbing proteins to bare PDMS in contrast to conventional techniques using a microcontact printing stamp. Given the several unique characteristics, the present technique based on the peel-off of inorganic materials may become a useful option for performing cell micropatterning.

Effects of spreading areas and aspect ratios of single cells on dedifferentiation of chondrocytes

Dedifferentiation of chondrocytes is common in culturing, and seriously affects the restorative efficacy of cartilage repair. The present study examines the effect of initial cell shapes on dedifferentiation of chondrocytes in vitro. The cell shape was controlled with a unique material micropatterning technique. With this technique, a series of microarrays of cell-adhesive peptide arginine-glycine-aspartate (RGD) were generated on a persistent non-fouling poly(ethylene glycol) (PEG) hydrogel. After culturing chondrocytes derived from rats on the micropatterned surfaces, the cell shapes were adapted by the geometries of adhesive microislands with pre-defined diameters (10, 15, 20 and 30 μm) for round ones and aspect ratios (1, 1.2, 1.5, 2, 4 and 6) for elliptical ones. After 10 days, collagen II staining was demonstrated to identify normal chondrocytes and dedifferentiated cells for those single cells on microislands. Furthermore, the gene expression of collagen II, collagen I, aggrecan and SOX9 were detected by qRT-PCR. The statistical results illustrated that dedifferentiation of chondrocytes happened more probably in the cases of larger sizes and higher aspect ratios. The conclusions stand under circumstances of both normoxia (21% O2) and hypoxia (5% O2) atmospheres.

One-Step Sub-10 μm Patterning of Carbon-Nanotube Thin Films for Transparent Conductor Applications

We propose a technique for one-step micropatterning of as-grown carbon-nanotube films on a plastic substrate with sub-10 μm resolution on the basis of the dry transfer process. By utilizing this technique, we demonstrated the novel high-performance flexible carbon-nanotube transparent conductive film with a microgrid structure, which enabled improvement of the performance over the trade-off between the sheet resistance and transmittance of a conventional uniform carbon-nanotube film. The sheet resistance was reduced by 46% at its maximum by adding the microgrid, leading to a value of 53 Ω/sq at a transmittance of 80%. We also demonstrated easy fabrication of multitouch projected capacitive sensors with 12 × 12 electrodes. The technique is quite promising for energy-saving production of transparent conductor devices with 100% material utilization.

Probabilistic density maps to study the spatial organization of endocytosis.

Despite a large body of publications on endocytosis, only a few studies have focused on its spatial organization. To study how endocytosis is related to distinct cellular sites, we combine cell normalization by the "micropatterning technique" with the quantification of spatial organization by "probabilistic density mapping." Micropatterns of extracellular matrix proteins impose adhesive and non-adhesive areas to cultured cells and allow the control of adhesion geometry, shape, and cell organization. Probabilistic density maps provide a visual summary for 3D localization of the structures of interest and enable the extraction of robust statistics for quantification of cellular organization. Here, we provide a method to analyze and compare the spatial distribution of endocytosed ligands in micropatterned cells. This approach permits to establish the role of cellular adhesion on uptake mechanisms and to address the potential function of predefined sites of endocytosis.

J0270102 新しい細胞マイクロパターニング技術の化学的裏付け([J027-01]細胞および分子のマイクロ・ナノスケール解析(1),バイオエンジニアリング部門)

Micropatterning is becoming a powerful tool for studying morphogenetic and differentiation processes of cells. Here we present a new micropatterning technique in which polydimethylsiloxane (PDMS) substrates were treated with oxygen plasma, and the resulting hydrophilic layer of the surface was locally peeled off through a direct contact with a peeling stamp. A hydrophobic layer of PDMS substrates could be selectively exposed only at the places of the physical contact, allowing for spatially selective adhesions of cells. Chemical bases for the successful cell micropatterning were confirmed with water contact angle measurements and X-ray photoelectron spectroscopy.

Creating Obstacle Courses for Raft Proteins - How Micropatterning Can Help Decipher Plasma Membrane Organization

According to prevailing theory, sterol- and sphingolipid enriched nanodomains exist in the mammalian plasma membrane but are too small and dynamic to allow for proper characterization. Attempts to artificially enhance putative tendencies in the plasma membrane to create optically resolvable phase separation have yielded new model systems like Giant Plasma Membrane Vesicles, bridging the gap between synthetic lipid bilayers and live cell membranes.In this work, we take those approaches one step further and attempt to create large scale phase separation in a live cell situation. To this end, we use a micropatterning technique to artificially create regions in the PM of live cells where we use a model raft protein glycosylphosphatidylinositol (GPI-GFP) is immobilized and highly enriched (via surface-immobilzed antibodies) at different densities to monitor the effects on plasma membrane organization and properties.Our key findings are: 1) Within patterned regions, we can immobilize and enrich GPI-GFP up to densities of 10,000 proteins/µm2 corresponding to average center-center distances of 9nm. 2) We do not observe colocalization of raft markers (CD59, cholera toxin) within GPI-GFP patterns. 2) The diffusion of CD59 is unhindered within patterns up to GPI-GFP obstacle distances of ∼17nm. At even small distances, the diffusion coefficient of CD59 decreases until a threshold is reached at ∼11nm. 3) A fluorescent cholesterol derivative diffuses virtually unhindered within patterns even at GPI-GFP distances of 9-10nm. Considering the size of the GPI-GFP obstacles and Fab-labeled CD59, the slowing of diffusion within patterns can probably be explained by steric hindrance alone, arguing against the association of either GPI-GFP or CD59 in nanodomains. We further find no evidence for the formation of a continuous raft phase or even an enrichment of a different, raft-like membrane phase within patterns.

A Live Cell Tirf-Microscopy Based Screening Assay for Fast Analysis of Receptor Tyrosine Kinase Modulators

Receptor tyrosine kinases (RTKs) are cell membrane receptors with intrinsic tyrosine kinase activity that trigger signal transduction. RTKs are known key regulators of essential cellular processes and have a critical role in the development of many types of cancer. Here we introduce an assay using micro-patterned surfaces in combination with TIRF microscopy for the analysis of EGF-receptor (EGFR) and insulin/insulin-like growth factor-receptor (IR/IGFR) downstream signaling. In addition, we applied the technique to validate the efficacy of medically relevant RTK modulators. We used micropatterning to force bait-EGFR/IR/IGFR molecules into microscopic domains on the surface of living cells, while monitoring co-recruitment of a fluorescent intracellular prey molecule (Grb2/IRS), respectively. First, micropatterning of HeLa cells expressing the prey Grb2 enabled us to quantify the EGFR-Grb2 interaction, and we could show that Grb2 was recruited to the EGFR in a phosphorylation dependent manner. Pretreatment with pharmacologically active ingredients used for the treatment of human cancers significantly reduced the inducibility of the signaling system. Based on these results we could set up a dose-response relationship in a live cell context. Second, we performed fluorescence recovery after photobleaching (FRAP) experiments with RKT class II receptors (IR and IGFR) and different cytosolic insulin receptor substrate (IRS) proteins. Our results indicate prominent differences in the interaction strength of IRS1 and IRS2 to the IR/IGF1-R, compared to the one of IRS3. Taken together the results approve the power of the micropatterning technique to study the interaction properties of plasma-membrane localized receptors. This method enables a fast analysis of the samples with high sensitivity in a live cell context. We could quantify the molecular effects of different RTK modulators and we will use the system in the near future to study further active pharmaceutical ingredients.

Cellular response to micropatterned growth promoting and inhibitory substrates

BackgroundNormal development and the response to injury both require cell growth, migration and morphological remodeling, guided by a complex local landscape of permissive and inhibitory cues. A standard approach for studying by such cues is to culture cells on uniform substrates containing known concentrations of these molecules, however this method fails to represent the molecular complexity of the natural growth environment.ResultsTo mimic the local complexity of environmental conditions in vitro, we used a contact micropatterning technique to examine cell growth and differentiation on patterned substrates printed with the commonly studied growth permissive and inhibitory substrates, poly-L-lysine (PLL) and myelin, respectively. We show that micropatterning of PLL can be used to direct adherence and axonal outgrowth of hippocampal and cortical neurons as well as other cells with diverse morphologies like Oli-neu oligodendrocyte progenitor cell lines and fibroblast-like COS7 cells in culture. Surprisingly, COS7 cells exhibited a preference for low concentration (1 pg/mL) PLL zones over adjacent zones printed with high concentrations (1 mg/mL). We demonstrate that micropatterning is also useful for studying factors that inhibit growth as it can direct cells to grow along straight lines that are easy to quantify. Furthermore, we provide the first demonstration of microcontact printing of myelin-associated proteins and show that they impair process outgrowth from Oli-neu oligodendrocyte precursor cells.ConclusionWe conclude that microcontact printing is an efficient and reproducible method for patterning proteins and brain-derived myelin on glass surfaces in order to study the effects of the microenvironment on cell growth and morphogenesis.

Special issue on tissue engineering

Tissue engineering is an emerging multidisciplinary research field that involves expertise related to cell biology, micro/ nanoscale engineering, and medicine. Engineering artificial tissues are of great benefit for restoring the lost function of diseased or damaged organs. The current research trends of tissue engineering aim to integrate cell-laden biodegradable scaffolds, microvasculatures, biomolecules, and micro/nanoscale engineering platforms. Due to its importance in human health, we select tissue engineering as a theme of this Special Issue of Biomedical Engineering Letters. This Special Issue introduces four review papers covering various state-of-theart technologies, including microengineering technologies, scaffold design and bio-inspired mechanics. The first paper entitled “Application of cellular micropatterns to miniaturized cell-based biosensor” is described by Koh and colleagues. Micropatterning enables the control of cell growth, differentiation, and apoptosis for cell-based sensor applications. Cellular detection on micropatterned substrates is generally performed by electrochemical methods (e.g., impedance-based electrochemical method, potential-based method) and optical methods (e.g., bioluminescence, fluorescence). The cellular micropatterning technique can also be integrated within microfluidics to enable high-throughput drug screening and discovery. Thus, this paper reviews the contemporary micropatterning technologies and their various miniaturized cell-based biosensor applications, such as multiphenotypic cell microarray, drug screening, and pathogen detection. Micropatterning techniques can also be used to fabricate microwells. Park and colleagues present an overview of “Microwell fabrication methods and applications for cellular studies”. This review introduces various fabrication techniques of microwells and mechanisms of cell trapping and handling. Microwells can be fabricated by soft lithography, implementation of physical forces, and micro-injection molding to manipulate the single cell trapping and cell aggregation. By using such microwell platforms, embryonic stem cells can be induced to form uniform-sized embryoid bodies that can be used to generate therapeutic cell types. The third paper entitled “Forming vascular networks within functional cardiac tissue constructs” is described by Bae and colleagues. Hydrogels are of great interest in scaffold fabrication for tissue engineering and regenerative medicine Bong Geun Chung ( ) Department of Mechanical Engineering, Sogang University, Seoul, Republic of Korea Tel : +82-2-705-8823 / Fax : +82-2-712-0799 E-mail : bchung@sogang.ac.kr

Synthesis and characterization of photochemical sol–gel derived lanthanum doped Bi4Ti3O12 film and its micro-patterns

A unique photochemical sol–gel route was employed to prepare La-doped Bi4Ti3O12 film (BLT) using bismuth nitrate, lanthanum nitrate, and titanium tetra-n-butoxide as starting materials. Through complex reaction between benzoyl acetone and Ti4+ ions, the synthesized La-doped Bi4Ti3O12 sol and gel films exhibited photosensitivity. Micro-patterned BLT film was obtained by a photoresist-free micro-patterning technique. The phase microstructures, electrical and ferroelectric properties of the as-prepared BLT film were characterized. By doping Lanthanum, the strong (00l)-oriented BT phase was transformed to randomly-oriented orthorhombic phase, resulting in the enhanced remanent polarization and improved fatigue properties. The obtained BLT film showed good ferroelectric properties with a long fatigue cycles over 1010 cycles.

Contactless Laser-Assisted Patterning of Surfaces for Bio-Adhesive Microarrays

Micropatterned surfaces with cell adhesive areas, delimited by protein repellent microstructures, are in high demand for its potential use as relevant biological assays. This is not only because such surfaces allow directing cell growth in a spatially localized and restricted manner, but also because they can be used to elucidate basic cell growth and orientation mechanisms. Here, it is presented a laser-assisted micropatterning technique to fabricate large area microstructures of poly (ethylene glycol) hydrogel onto a cell adhesive surface: a biofunctional maleic anhydride copolymer. By varying photoinitiator, laser intensity, copolymer as well as the hydrogel layer thickness, the optimum conditions to produce high quality features were found. The suitability of these micropatterned substrates for bioassay applications was proved by cell adhesion studies. The introduced procedure could be used to prepare a broad range of microarrays for certain bioanalytical approaches and to create different types of biofunctional surfaces.