Ernest F. Hasselbrink

Biomolecular motor-driven molecular sorter

We have developed a novel, microfabricated, stand-alone microfluidic device that can efficiently sort and concentrate (bio-)analyte molecules by using kinesin motors and microtubules as a chemo-mechanical transduction machine. The device removes hundreds of targeted molecules per second from an analyte stream by translocating functionalized microtubules with kinesin across the stream and concentrating them at a horseshoe-shaped collector. Target biomolecule concentrations increase up to three orders of magnitude within one hour of operation.

Biomolecular motor-driven microtubule translocation in the presence of shear flow: Analysis of redirection behaviours

We suggest a concept for powering microfluidic devices with biomolecular motors and microtubules to meet the demands for highly efficient microfluidic devices. However, to successfully implement such devices, we require methods for active control over the direction of microtubule translocation. While most previous work has employed largely microfabricated passive mechanical patterns designed to guide the direction of microtubules, in this paper we demonstrate that hydrodynamic shear flow can be used to align microtubules translocating on a kinesin-coated surface in a direction parallel to the fluid flow. Our evidence supports the hypothesis that the mechanism of microtubule redirection is simply that drag force induced by viscous shear bends the leading end of a microtubule, which may be cantilevered beyond its kinesin supports. This cantilevered end deflects towards the flow direction, until it is subsequently bound to additional kinesins; as translocation continues, the process repeats until the microtubule is largely aligned with the flow, to a limit determined by random fluctuations created by thermal energy. We present statistics on the rate of microtubule alignment versus various strengths of shear flow as well as concentrations of kinesin, and also investigate the effects of shear flow on the motility.

Mobile Flow Control Elements for High-Pressure Micro-Analytical Systems Fabricated Using in-Situ Polymerization

A method for rapidly fabricating a family of robust fluid control elements in microfluidic channels is presented. The polymer devices are lithographically defined in situ in glass microfluidic channels in a few seconds on a benchtop. The devices are capable of controlling fluid flow in microchannels at pressures exceeding 5000 psi (340 bar) and can be actuated in milliseconds. In this work we demonstrate chip-based devices, including a piston, check-valve, and a 10 nanoliter pipette.

The physics and limits of femtosecond laser micromachining

Laser-induced optical breakdown by femtosecond pulses is extraordinarily precise when the energy is near threshold. We examine the limits of femtosecond machining through studies of damage induced by tightly focused pulses in a variety of materials.

Limits of ultrafast nanomachining: bubble dynamics and acoustics

Acoustic phenomena during nanochannel machining by fs laser pulses are found to have an unexpected strong influence on the machining efficiency. Analysis of acoustic nodes that strongly limit machining efficiency allows strategies to be identified for fabrication of high aspect ratio channels. Based on an analytic solution for node formation, it is found that increasing the speed of acoustic transmission can produce a two-fold increase in the length of the channels; this can be accomplished by maximizing the mole fraction of hydrogen in the gas phase. The model is further reinforced by the effects of varying pressure.

A computational model of a novel biomolecular microfluidics pump

We are developing a novel microfluidics pump, which is powered by biomolecular motors. The performance and feasibility of this pump design is investigated using the boundary element method.