Synthesis and characterization of biocompatible nanodiamond-silk hybrid material.

A new hybrid material consisting of nanodiamonds (NDs) and silk has been synthesized and investigated. NDs can contain bright fluorescence centers, important for bioprobes to image biological structures at the nanoscale and silk provides a transparent, robust matrix for these nanoparticles in-vivo or in-vitro. The ND-silk hybrid films were determined to be highly transparent in the visible to near infrared wavelength range.

Measuring the dispersive properties of liquids using a microinterferometer.

Using a single-beam, compact interferometer, we measure the refractive index of liquids in the near IR. This highly compact device relies on a silica capillary with a 50 μm inner diameter: it uses a minimal volume of test liquid, isolates the liquid from the humid atmosphere, has broadband operation, and is inherently mechanically stable. These characteristics, in combination with straightforward data acquisition, make it particularly well-suited for measuring the optical properties in the near IR of a wide range of liquids.

Bio-microfluidics: biomaterials and biomimetic designs.

Bio-microfluidics applies biomaterials and biologically inspired structural designs (biomimetics) to microfluidic devices. Microfluidics, the techniques for constraining fluids on the micrometer and sub-micrometer scale, offer applications ranging from lab-on-a-chip to optofluidics. Despite this wealth of applications, the design of typical microfluidic devices imparts relatively simple, laminar behavior on fluids and is realized using materials and techniques from silicon planar fabrication.

Bioactive "self-sensing" optical systems.

Free-standing silk films are useful materials to manufacture nanopatterned optical elements and to immobilize bio-dopants such as enzymes while maintaining their biological activity. These traits were combined by incorporating hemoglobin into free-standing silk diffraction gratings to fabricate chemically responsive optofluidic devices responsive to ambient gas conditions, constituting a simple oxygen sensor. This type of self-analyzing optical system is enabled by the unique ability to reproduce high-fidelity optical structures in silk while maintaining the activity of entrapped proteins such as hemoglobin.

Facile fabrication of gelatin-based biopolymeric optical waveguides.

The rapid development in optical detection techniques for sensing applications has led to an increased need for biocompatible, biodegradable, and disposable optical components. We present a controllable fabrication technique for an entirely biopolymeric planar optical waveguide via simple spin-coating. The refractive index difference, thermal responsive properties, and inherent biocompatibility of gelatin and agarose were exploited in the fabrication of thin, stacked films that efficiently guide light in a core layer with higher index of refraction.

Planar microfluidic chamber for generation of stable and steep chemoattractant gradients.

The extracellular availability of growth factors, hormones, chemokines, and neurotransmitters under gradient conditions is required for directional cellular responses such as migration, axonal pathfinding, and tissue patterning. These responses are, in turn, important in disease and developmental processes. This article addresses critical barriers toward devising a chemotaxis assay that is broadly applicable for different kinds of cancer cells through the design of a microfluidic chamber that produces a steep gradient of chemoattractant.

Transverse characterization of high air-fill fraction tapered photonic crystal fiber.

We demonstrate tapering of a high air-fill fraction photonic crystal fiber by using the flame-brushing technique. Transverse probing along the taper allows us to ascertain how the microstructure is preserved during tapering. Experimental results are compared with numerical simulations performed with the finite-difference time-domain and plane-wave expansion methods.

A new slant on photonic crystal fibers.

We present the novel use of microstructured optical fibers not as "light-pipes", but in a transverse geometry to manipulate the light propagating across the fiber. Fundamental and higher-order bandgaps were observed experimentally in this geometry using a number of techniques. The comparison of the measured spectra with photonic band structure and Finite-Difference Time-Domain simulations provide strong evidence that the spectral features are a result of the periodic nature of the fiber microstructure in the transverse direction.