Two kinds of biomimetic systems including engineered organ chip and flexible electronic sensor are presented. First, <i>in vivo</i>, renal tubular epithelial cells are exposed to luminal fluid shear stress (FSS) and a transepithelial osmotic gradient. In this study, we used a simple collecting-duct-on-a-chip to investigate the role of an altered luminal microenvironment in the translocation of aquaporin-2 (AQP2) and the reorganization of actin cytoskeleton (F-actin) in primary cultured inner medullary collecting duct (IMCD) cells of rat kidney. We demonstrate that several factors (i.e., luminal FSS, hormonal stimulation, transepithelial osmotic gradient) collectively exert a profound effect on the AQP2 trafficking in the collecting ducts, which is associated with actin cytoskeletal reorganization. Furthermore, with this kidney-mimicking chip, renal toxicity of cisplatin was tested under static and fluidic conditions, suggesting the physiological relevancy of fluidic environment compared to static culture. Second, we present a simple architecture for a flexible and highly sensitive strain sensor that enables the detection of pressure, shear and torsion. The device is based on two interlocked arrays of high-aspect-ratio Pt-coated polymeric nanofibres that are supported on thin polydimethylsiloxane layers. When different sensing stimuli are applied, the degree of interconnection and the electrical resistance of the sensor changes in a reversible, directional manner with specific, discernible strain-gauge factors. We show that the sensor can be used to monitor signals ranging from human heartbeats to the impact of a bouncing water droplet on a superhydrophobic surface.
We report a large-area, dual-scale metal transfer method by using a difference in adhesive force. Rigiflex
polyurethane acrylate (PUA) molds with engraved nanoscale patterns were used to transfer metal layers (Au or
Al) to flexible polyethylene terephthalate (PET) substrate. Transfer process was performed sequentially for the
metal layers on ridge and valley regions of the mold, resulting in a dual-scale metal transfer from a single master.
A simple metal wire grid polarizer was fabricated and analyzed using this method.
We present a simple method for fabricating high aspect-ratio polymer nanostructures on a solid substrate by sequential application of molding and drawing of a thin polymer film. In this method, a thin polymer film is prepared by spin coating on a solid substrate and the temperature is raised above the polymer's glass transition while in conformal contact with a poly(urethane acrylate) (PUA) mold having nano-cavities. Consequently, capillary force induces deformation of the polymer melt into the void spaces of the mold and the filled nanostructure was further elongated upon removal of the mold due to tailored adhesive force at the mold/polymer interface. The optimum value of the work of adhesion at the mold/polymer interface ranged from 0.9 to 1.1 times that at the substrate/polymer interface. Below or above this range, a simple molding or detachment occurred, corresponding to earlier findings.
A simple method for fabricating micro/nanoscale hierarchical structures is presented using a two-step temperature-directed capillary molding technique. This lithographic method involves a sequential application of molding process in which a uniform polymer-coated surface is molded with a patterned mold by means of capillary force above the glass transition temperature of the polymer. Various microstructures and nanostructures were fabricated with minimum
resolution down to ~ 50 nm with good reproducibility. Also contact angle measurements of water indicated that two wetting states coexist on a multiscale hierarchical structure where heterogeneous wetting is dominant for microstructure and homogeneous wetting for nanostructure. A simple theoretical model combining these two wetting states was presented, which was in good agreement with the experimental data. Using this approach, multiscale hierarchical
structures for biomimetic functional surfaces can be fabricated with precise control over geometrical parameters and the wettability of a solid surface can be tailored in a controllable manner.
We present a simple method to generate nanostructures without residual layer using detachment-based nanolithography. Spin coated organic thin film and patterned stamp such as ultraviolet (UV) curable mold were prepared. The mold and organic thin film were contacted by slight pressure (1~2 bar). While conformal contact between mold and organic thin film, the sample was heated under the glass transient temperature. After cooling to room temperature, the mold was removed from substrate, rendering a pattern organic layer without residual layer. This method can form as small as 70 nm lines.