Directing cell migration and organization via nanocrater-patterned cell-repellent interfaces.

Although adhesive interactions between cells and nanostructured interfaces have been studied extensively, there is a paucity of data on how nanostructured interfaces repel cells by directing cell migration and cell-colony organization. Here, by using multiphoton ablation lithography to pattern surfaces with nanoscale craters of various aspect ratios and pitches, we show that the surfaces altered the cells focal-adhesion size and distribution, thus affecting cell morphology, migration and ultimately localization. We also show that nanocrater pitch can disrupt the formation of mature focal adhesions to favour the migration of cells towards higher-pitched regions, which present increased planar area for the formation of stable focal adhesions. Moreover, by designing surfaces with variable pitch but constant nanocrater dimensions, we were able to create circular and striped cellular patterns. Our surface-patterning approach, which does not involve chemical treatments and can be applied to various materials, represents a simple method to control cell behaviour on surfaces

Contractile deficits in engineered cardiac microtissues as a result of MYBPC3 deficiency and mechanical overload.

The integration of in vitro cardiac tissue models, human induced pluripotent stem cells (hiPSCs) and genome-editing tools allows for the enhanced interrogation of physiological phenotypes and recapitulation of disease pathologies. Here, using a cardiac tissue model consisting of filamentous three-dimensional matrices populated with cardiomyocytes derived from healthy wild-type (WT) hiPSCs (WT hiPSC-CMs) or isogenic hiPSCs deficient in the sarcomere protein cardiac myosin-binding protein C (MYBPC3-/- hiPSC-CMs), we show that the WT microtissues adapted to the mechanical environment with increased contraction force commensurate to matrix stiffness, whereas the MYBPC3-/- microtissues exhibited impaired force development kinetics regardless of matrix stiffness and deficient contraction force only when grown on matrices with high fibre stiffness. Under mechanical overload, the MYBPC3-/- microtissues had a higher degree of calcium transient abnormalities, and exhibited an accelerated decay of calcium dynamics as well as calcium desensitization, which accelerated when contracting against stiffer fibres. Our findings suggest that MYBPC3 deficiency and the presence of environmental stresses synergistically lead to contractile deficits in cardiac tissues

Quantitative analysis of single bacterial chemotaxis using a linear concentration gradient microchannel

A microfluidic device to quantify bacterial chemotaxis has been proposed, which generates a linear concentration gradient of chemoattractant in the main channel only by convective and molecular diffusion, and which enables the bacteria to enter the main channel in a single file by hydrodynamic focusing technique. The trajectory of each bacterium in response to the concentration gradient of chemoattractant is photographed by a CCD camera and its velocity is acquired by a simple PTV (Particle Tracking Velocimetry) algorithm. An advantage of this assay is to measure the velocity of a single bacterium and to quantify the degree of chemotaxis by analyzing the frequency of velocities concurrently. Thus, the parameter characterizing the motility of wild-type Escherichia coli strain RP437 in response to various concentration gradients of L-aspartate is obtained in such a manner that the degree of bacterial chemotaxis is quantified on the basis of a newly proposed Migration Index

Functionalization and Multi-Dimensional Structure Fabrication using Ultrafast Laser Direct Writing (FS-LDW)

Femtosecond laser-direct writing (FS-LDW) can functionalize the surface of diverse device components, including cell culture plates and medical implants. Since FS-LDW is in essence a non-contact fabrication method, it allows the surface patterning and micro-/nano-machining of material with minimal mechanical/thermal deformation. Hence, micro-/nanofabrication and material processing by femtosecond laser has attracted intense interest.Ultrafast laser ablation using far-field optics in a tight focusing configuration offers substantial advantages for the direct, maskless and arbitrary patterning of various materials and curved surfaces, while maintaining high feature resolution. Patterned surfaces with nanoscale craters or ablated pattern on electrospinning fibrous scaffolds can control and direct the cell migration. Control of topographical features in the cellular microenvironment can be achieved by combining FS-LDW with new materials. Direct laser writing by multi-photon polymerization is a nonlinear optical technique that allows the fabrication of 3D structures with resolution beyond the diffraction limit (~100nm). Incorporation of self-assembled block-copolymer nanomaterials into such structure fabricated by two-photon polymerization and, produced mesoscale structures endowed with guided nanoscale patterns (~10nm). This new capability can be used in many applications, including advanced optical metamaterials as well as for efficient photovoltaic energy conversion. In contrast, using low numerical aperture objective lens, fast fibrous structure (high aspect ratio) fabrication is possible. Well-organized fibrous structure can be used for patient-/disease-specific drug testing platform.Femtosecond laser direct writing is promising technique that can induce surface (e.g., via ablation) or volumetric patterning in a serial fashion (multi-photon polymerization). We applied these techniques to design and control multi-functional platform fabrication. As a result, FS-LDW fabricated structures exhibit higher resolution fabrication, and efficient functionality (e.g., in controlling the migration on 2D and 3D structure / tuning of mechanical stiffness of structure / directed self-assembly of block copolymer / enhancement of fluidic mixing

Functionalization and Multi-Dimensional Structure Fabrication using Ultrafast Laser Direct Writing (FS-LDW)

Femtosecond laser-direct writing (FS-LDW) can functionalize the surface of diverse device components, including cell culture plates and medical implants. Since FS-LDW is in essence a non-contact fabrication method, it allows the surface patterning and micro-/nano-machining of material with minimal mechanical/thermal deformation. Hence, micro-/nanofabrication and material processing by femtosecond laser has attracted intense interest.Ultrafast laser ablation using far-field optics in a tight focusing configuration offers substantial advantages for the direct, maskless and arbitrary patterning of various materials and curved surfaces, while maintaining high feature resolution. Patterned surfaces with nanoscale craters or ablated pattern on electrospinning fibrous scaffolds can control and direct the cell migration. Control of topographical features in the cellular microenvironment can be achieved by combining FS-LDW with new materials. Direct laser writing by multi-photon polymerization is a nonlinear optical technique that allows the fabrication of 3D structures with resolution beyond the diffraction limit (~100nm). Incorporation of self-assembled block-copolymer nanomaterials into such structure fabricated by two-photon polymerization and, produced mesoscale structures endowed with guided nanoscale patterns (~10nm). This new capability can be used in many applications, including advanced optical metamaterials as well as for efficient photovoltaic energy conversion. In contrast, using low numerical aperture objective lens, fast fibrous structure (high aspect ratio) fabrication is possible. Well-organized fibrous structure can be used for patient-/disease-specific drug testing platform.Femtosecond laser direct writing is promising technique that can induce surface (e.g., via ablation) or volumetric patterning in a serial fashion (multi-photon polymerization). We applied these techniques to design and control multi-functional platform fabrication. As a result, FS-LDW fabricated structures exhibit higher resolution fabrication, and efficient functionality (e.g., in controlling the migration on 2D and 3D structure / tuning of mechanical stiffness of structure / directed self-assembly of block copolymer / enhancement of fluidic mixing

Green Synthesis of Nanoparticles Using Bio-Inspired Systems and Electrically Conductive Pattern Fabrication through Laser-Direct Writing

Systems existing in nature have evolved to operate efficiently over a long period of time, enabling efficient material transformation and processing. These natural systems provide hints for the synthesis of metal nanoparticles through efficient electron generation and transport towards metal ions for the reduction process. In this study, based on the efficient electron transfer mechanism between tryptophan (Trp) in the living body, the possibility of advanced silver patterning on flexible substrates has been presented through laser-direct writing. Irradiation of a low-power laser on the precursor induces the reduction of silver ions to nanoparticles. The sintering of these generated nanoparticles induces a silver conductive pattern by a photothermal/chemical reaction. The method of this study has strength as it supports the possibility of conductive pattern fabrication on various substrates (e.g., glass and PDMS) using a silver-based organic ink with low laser power compared to the conventional nanoparticle-based sintering method. It also suggests its suitability to various applications in terms of sophisticated pattern fabrication with minimized substrate denaturation

Advanced Micro-Actuator/Robot Fabrication Using Ultrafast Laser Direct Writing and Its Remote Control

Two-photon polymerization (TPP) based on the femtosecond laser (fs laser) direct writing technique in the realization of high-resolution three-dimensional (3D) shapes is spotlighted as a unique and promising processing technique. It is also interesting that TPP can be applied to various applications in not only optics, chemistry, physics, biomedical engineering, and microfluidics but also micro-robotics systems. Effort has been made to design innovative microscale actuators, and research on how to remotely manipulate actuators is also constantly being conducted. Various manipulation methods have been devised including the magnetic, optical, and acoustic control of microscale actuators, demonstrating the great potential for non-contact and non-invasive control. However, research related to the precise control of microscale actuators is still in the early stages, and in-depth research is needed for the efficient control and diversification of a range of applications. In the future, the combination of the fs laser-based fabrication technique for the precise fabrication of microscale actuators/robots and their manipulation can be established as a next-generation processing method by presenting the possibility of applications to various areas

Flexible Heater Fabrication Using Amino Acid-Based Ink and Laser-Direct Writing

Nature’s systems have evolved over a long period to operate efficiently, and this provides hints for metal nanoparticle synthesis, including the enhancement, efficient generation, and transport of electrons toward metal ions for nanoparticle synthesis. The organic material-based ink composed of the natural materials used in this study requires low laser power for sintering compared to conventional nanoparticle ink sintering. This suggests applicability in various and sophisticated pattern fabrication applications without incurring substrate damage. An efficient electron transfer mechanism between amino acids (e.g., tryptophan) enables silver patterning on flexible polymer substrates (e.g., PET) by laser-direct writing. The reduction of silver ions to nanoparticles was induced and sintered by simultaneous photo/thermalchemical reactions on substrates. Furthermore, it was possible to fabricate a stable, transparent, and flexible heater that operates under mechanical deformation

Selective epitaxial growth of stepwise SiGe:B at the recessed sources and drains: A growth kinetics and strain distribution study

The selective epitaxial growth of Si1-xGex and the related strain properties were studied. Epitaxial Si1-xGex films were deposited on (100) and (110) orientation wafers and on patterned Si wafers with recessed source and drain structures via ultrahigh vacuum chemical vapor deposition using different growing steps and Ge concentrations. The stepwise process was split into more than 6 growing steps that ranged in thicknesses from a few to 120 nm in order to cover the wide stages of epitaxial growth. The growth rates of SiGe on the plane and patterned wafers were examined and a dependence on the surface orientation was identified. As the germanium concentration increased, defects were generated with thinner Si1-xGex growth. The defect generation was the result of the strain evolution which was examined for channel regions with a Si1-xGex source/drain (S/D) structure

Stretchable energy-harvesting tactile electronic skin capable of differentiating multiple mechanical stimuli modes

The first stretchable energy harvesting e-skin (EHES) that is able to detect, differentiate, and harvest a variety of mechanical stimuli, enabled by the stretchability of the device and a unique device architecture was reported. Using PDMS microstructuring in combination with an air gap, the researchers enabled pressure sensing from several pascals to tens of kilopascals. The device was capable of differentiating different tactile signals by measuring three different output signals (capacitance, resistance of the top and resistance of the bottom electrode). The capacitive design was important since the top and the bottom electrodes needed to be electrically isolated so that the measured change in film resistance was only due to the lateral straining of each film, not due to the electrical conduction between the top and bottom electrodes. Capacitive sensor design also enabled energy-harvesting functionality along with its sensing capability. envision that our energy-harvesting e-skin and the concepts introduced here can be utilized in the future to enable a fully self-sustainable skin-like devices with stretchability, multifunctional tactile sensing, and energy-harvesting capability © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim11451551sciescopu