Nanoimprint lithography and physical vapor deposition were combined to fabricate large-area homogeneously patterned SERS-active substrates with tunable surface plasmon resonances. The plasmon shift observed was connected to the surface nanotopography since (a) the SERS-active nanoparticles on all the substrates investigated were shown to be chemically and structurally similar and (b) the SERS spectra of the analyte investigated were essentially identical for all samples. In addition, the tunability of surface nanotopography was shown to boost the SERS effect via optimal coupling between the substrate's SPR and the incident laser line.

Nanoscale batteries with anode-Li4Ti5O12 (LTO) and cathode-LiFePO4 (LFP) have shown a significant potential to develop long-life and high-rate Li-ion batteries.

We developed a hybrid nanoimprint-soft lithography technique with sub-15 nm resolution. It is capable of patterning both flat and curved substrates. The key component of the technology is the mold, which consists of rigid features on an elastic poly(dimethylsiloxane) (PDMS) support. The mold was fabricated by imprinting a reverse image onto the PDMS substrate using a UV-curable low-viscosity prepolymer film. Patterns with sub-15-nm resolution were faithfully duplicated on a flat substrate without applying external pressure. Gratings at 200 nm pitch were also successfully imprinted onto the cylindrical surface of a single mode optical fiber with a 125 µm diameter.

Microneedle technologies have the potential for expanding the capabilities of wearable health monitoring from physiology to biochemistry. This paper presents the fabrication of silicon hollow microneedles by a deep-reactive ion etching (DRIE) process, with the aim of exploring the feasibility of microneedle-based in-vivo monitoring of biomarkers in skin fluid. Such devices shall have the ability to allow the sensing elements to be integrated either within the needle borehole or on the backside of the device, relying on capillary filling of the borehole with dermal interstitial fluid (ISF) for transporting clinically relevant biomarkers to the sensor sites. The modified DRIE process was utilized for the anisotropic etching of circular holes with diameters as small as 30 μm to a depth of >300 μm by enhancing ion bombardment to efficiently remove the fluorocarbon passivation polymer. Afterward, isotropic wet and/or dry etching was utilized to sharpen the needle due to faster etching at the pillar top, achieving tip radii as small as 5 μm. Such sharp microneedles have been demonstrated to be sufficiently robust to penetrate porcine skin without needing any aids such as an impact-insertion applicator, with the needles remaining mechanically intact after repetitive penetrations. The capillary filling of DRIE-etched through-wafer holes with water has also been demonstrated, showing the feasibility of use to transport the analyte to the target sites.

The organization of cells and extracellular matrix (ECM) in native tissues plays a crucial role in their functionality. However, in tissue engineering, cells and ECM are randomly distributed within a scaffold. Thus, the production of engineered-tissue with complex 3D organization remains a challenge. In the present study, we used contact guidance to control the interactions between the material topography, the cells and the ECM for three different tissues, namely vascular media, corneal stroma and dermal tissue. Using a specific surface topography on an elastomeric material, we observed the orientation of a first cell layer along the patterns in the material. Orientation of the first cell layer translates into a physical cue that induces the second cell layer to follow a physiologically consistent orientation mimicking the structure of the native tissue. Furthermore, secreted ECM followed cell orientation in every layer, resulting in an oriented self-assembled tissue sheet. These self-assembled tissue sheets were then used to create 3 different structured engineered-tissue: cornea, vascular media and dermis. We showed that functionality of such structured engineered-tissue was increased when compared to the same qnon-structured tissue. Dermal tissues were used as a negative control in response to surface topography since native dermal fibroblasts are not preferentially oriented in vivo. Non-structured surfaces were also used to produce randomly oriented tissue sheets to evaluate the impact of tissue orientation on functional output. This novel approach for the production of more complex 3D tissues would be useful for clinical purposes and for in vitro physiological tissue model to better understand long standing questions in biology.

This work demonstrates the fabrication of metallic nanoprism (triangular nanostructure) arrays using a low-cost and high-throughput process. In the method, the triangular structure is defined by the shadow of a pyramid during angle evaporation of a metal etching mask. The pyramids were created by nanoimprint lithography in polymethylmethacrylate (PMMA) using a mould having an inverse-pyramid-shaped hole array formed by KOH wet etching of silicon. Silver and gold nanoprism arrays with a period of 200 nm and an edge length of 100 nm have been fabricated and used as effective substrates for surface enhanced Raman spectroscopy (SERS) detection of rhodamine 6G (R6G) molecules. Numerical calculations confirmed the great enhancement of electric field near the sharp nanoprism corners, as well as the detrimental effect of the chromium adhesion layer on localized surface plasmon resonance. The current method can also be used to fabricate non-equilateral nanoprism and three-dimensional (3D) nanopyramid arrays, and it can be readily extended to other metals.

In vivo, cardiomyocytes are exposed to multiple biochemical and physical cues including topographical and electrical cues. During prolonged in vitro cultivation in standard tissue culture set-ups, cardiomyocytes are known to de-differentiate due to the lack of appropriate micro-environmental cues. Most currently available cell culture systems provide only a single biophysical cue, thus development of advanced cell cultivation systems incorporating multiple cues is urgently needed. We report here the development of a microfabricated system, incorporating topographical and electrical cues on a single chip, which enables cultivation of differentiated cardiomyocytes. The cell culture chips were created by hot embossing of polystyrene, to create microgrooves and microridges of precisely defined depth, width and periodicity. Substrates consisting of 0.5 microm-wide grooves and 0.5 microm-wide ridges (1 microm period) and those consisting of 3 microm-wide grooves and 1 microm-wide ridges (4 microm period) were investigated, with smooth surfaces used as controls. The depth of the microgrooves was 400 nm. The two gold electrodes were electrodeposited 1 cm apart such that the microgrooves in-between were oriented either parallel or perpendicular to the electrodes, enabling studies of interaction between topographical and electrical cues. Neonatal rat cardiomyocytes cultivated on microgrooved substrates for 7 days were elongated and aligned along the microgrooves forming a well developed contractile apparatus, as evidenced by sarcomeric alpha-actinin staining, with a more pronounced effect on substrates with 1 microm compared to 4 microm periodicity. Importantly, simultaneous application of biphasic electrical pulses and topographical cues resulted in gap junctions confined to the cell-cell end junctions rather than the punctate distribution found in neonatal cells. Electrical field stimulation further enhanced cardiomyocyte elongation when microgrooves were oriented parallel to the electric field. Due to the compatibility of the described cell culture chips with fluorescence and optical microscopy as well as the ability to independently control field stimulation parameters, biochemical and topographical cues on each chip, this system may in the future become a useful tool in drug development and maturation of cardiomyocytes derived from stem cells.

Long-range ordered noble-metal nanocrescent arrays of different sizes and shapes have been successfully fabricated by using both nanoimprint lithography and e-beam lithography techniques. Large surface enhanced Raman scattering (SERS) enhancements in the detection of rhodamine 6G (R6G) molecules on these arrays have been observed and attributed to the enhancement of the local electromagnetic (EM) fields near individual nanocrescents. Electromagnetic enhancement factors for crescents of different shapes are computed using the discrete dipole approximation and compared with experimental measurements of the R6G Raman intensities. It is found that the maximum values of SERS intensity appear at an intermediate value of the crescent eccentricity and the observed behaviour is related to the spatial distributions of the enhancement of the local EM field (hot spots).