Electron beam fabrication of a microfluidic device for studying submicron-scale bacteria.

Background: Controlled restriction of cellular movement using microfluidics allows one to study individual cells to gain insight into aspects of their physiology and behaviour. For example, the use of micron-sized growth channels that confine individual Escherichia coli has yielded novel insights into cell growth and death. To extend this approach to other species of bacteria, many of whom have dimensions in the sub-micron range, or to a larger range of growth conditions, a readily-fabricated device containing sub-micron features is required.

Calibration of the optical torque wrench.

The optical torque wrench is a laser trapping technique that expands the capability of standard optical tweezers to torque manipulation and measurement, using the laser linear polarization to orient tailored microscopic birefringent particles. The ability to measure torque of the order of kBT (∼4 pN nm) is especially important in the study of biophysical systems at the molecular and cellular level. Quantitative torque measurements rely on an accurate calibration of the instrument.

Electron beam fabrication of birefringent microcylinders.

Numerous biological and biotechnological applications rely on the use of micrometer- and nanometer-scale particles, benefiting tremendously from quantitative control of their physical and chemical properties. Here, we describe the use of electron beam lithography for the design, fabrication, and functionalization of micrometer-scale birefringent quartz cylinders for use in sensing and detection. We demonstrate excellent control of the cylinders' geometry, fabricating cylinders with heights of 0.

Controlling the surface properties of nanostructures for studies of polymerases.

We report the successful functionalization of optically accessible nanostructures, suitable for single-molecule experiments at physiological substrate concentrations, with polyethylene glycol. Characterization of the coating in terms of roughness, protein repellence, and specific immobilization of DNA is described. We present an application of this technique in the detection of polymerase activity within nanostructures, which demonstrates the opportunities made possible through the integration of nanofabricated structures with surface functionalization.

Navigation in a small world with local information.

It is commonly known that there exist short paths between vertices in a network showing the small-world effect. Yet vertices, for example, the individuals living in society, usually are not able to find the shortest paths, due to the very serious limit of information. To study this issue theoretically, here the navigation process of launching messages toward designated targets is investigated on a variant of the one-dimensional small-world network (SWN).