Controlled gating and electrical detection of single 50S ribosomal subunits through a solid-state nanopore in a microfluidic chip.

We describe analysis and control of 50S ribosomal subunits by a solid-state 45nm diameter nanopore incorporated in a microfluidic chip. When used as a resistive pulse sensor, translocation of single 50S subunits through the nanopore produces current blockades that have a linear dependence on applied voltage. Introduction of individual subunits into the fluidic channel shows a threshold behavior that allows controlled entry of individual 50S ribosomal subunits. The incorporation of nanopores into a larger optofluidic chip system opens possibilities for electrical and optical studies of single ribosomes in well-defined and rapidly variable chemical environments.

Hollow ARROW Waveguides on Self-Aligned Pedestals for Improved Geometry and Transmission.

Micrometer-sized hollow antiresonant reflecting optical waveguides on silicon substrates have been previously demonstrated with liquid and gas-filled cores. Previous designs have nonideal geometries, with nonuniform lateral layers around the hollow core, resulting in higher loss than could potentially be achieved. A new design and fabrication process has been developed involving hollow waveguide fabrication on a self-aligned pedestal (SAP) using anisotropic plasma etching. With the SAP structure, the hollow core is surrounded by uniform layers and a terminal layer of air on three sides, resulting in air-core waveguide loss of 1.54 cm(-1) at 785 nm and high fabrication yield.

Multi-mode mitigation in an optofluidic chip for particle manipulation and sensing.

A new waveguide design for an optofluidic chip is presented. It mitigates multi-mode behavior in solid and liquid-core waveguides by increasing fundamental mode coupling to 82% and 95%, respectively. Additionally, we demonstrate a six-fold improvement in lateral confinement of optically guided dielectric microparticles and double the detection efficiency of fluorescent particles.

Improving solid to hollow core transmission for integrated ARROW waveguides.

Optical sensing platforms based on anti-resonant reflecting optical waveguides (ARROWs) with hollow cores have been used for bioanalysis and atomic spectroscopy. These integrated platforms require that hollow waveguides interface with standard solid waveguides on the substrate to couple light into and out of test media. Previous designs required light at these interfaces to pass through the anti-resonant layers.We present a new ARROW design which coats the top and sides of the hollow core with only SiO2, allowing for high interface transmission between solid and hollow waveguides. The improvement in interface transmission with this design is demonstrated experimentally and increases from 35% to 79%. Given these parameters, higher optical throughputs are possible using single SiO2 coatings when hollow waveguides are shorter than 5.8 mm.

Hollow-core waveguide characterization by optically induced particle transport.

We introduce a method for optical characterization of hollow-core optical waveguides. Radiation pressure exerted by the waveguide modes on dielectric microspheres is used to analyze salient properties such as propagation loss and waveguide mode profiles. These quantities were measured for quasi-single-mode and multimode propagation in on-chip liquid-filled hollow-core antiresonant reflecting optical waveguides. Excellent agreement with analytical and numerical models is found, demonstrating that optically induced particle transport provides a simple, inexpensive, and nondestructive alternative to other characterization methods.

Planar optofluidic chip for single particle detection, manipulation, and analysis.

We present a fully planar integrated optofluidic platform that permits single particle detection, manipulation and analysis on a chip. Liquid-core optical waveguides guide both light and fluids in the same volume. They are integrated with fluidic reservoirs and solid-core optical waveguides to define sub-picoliter excitation volumes and collect the optical signal, resulting in fully planar beam geometries. Single fluorescently labeled liposomes are used to demonstrate the capabilities of the optofluidic chip. Liposome motion is controlled electrically, and fluorescence correlation spectroscopy (FCS) is used to determine concentration and dynamic properties such as diffusion coefficient and velocity. This demonstration of fully planar particle analysis on a semiconductor chip may lead to a new class of planar optofluidics-based instruments.

Optical characterization of arch-shaped ARROW waveguides with liquid cores.

We present the characterization of the optical properties of integrated antiresonant reflecting optical (ARROW) waveguides with arch-shaped liquid cores. Optical mode shapes and coupling, waveguide loss, and polarization dependence are investigated. Waveguide loss as low as 0.26/cm with near-single-mode coupling and mode areas as small as 4.5microm2 are demonstrated. A detailed comparison to ARROW waveguides with rectangular cores is presented, and shows that arch-shaped cores are superior for many applications.