The objective of this proposal is to establish a new basis of far field nanoscopic velocimetry and apply this novel method to study fundamentals of transport phenomena in nanofluidic systems through directly measuring the transient flow velocity and velocity distribution in nanochannels. The proposed research will (1) explore both the science and technology necessary to realize a novel diagnostic technology capable of measuring the transient flow velocity distribution in a nanochannel with high temporal (~1 ìs) and spatial (10-20 nm) resolution; (2) apply this enabling farfield nanoscopic measurement system to study transport phenomena, velocity distribution and slip length, and gain a more fundamental understanding of different phenomena in nanofluidics. If successful, this will be achieved through a nanoscale focused laser beam, an essential component for achieving spatial resolution beyond the well known Abbe's diffraction resolution limit. The combination of a nanoscale focused laser beam with a molecular tracer based velocimetry has the potential to serve as the foundation for the proposed nanovelocimetry capable of unprecedented velocity measurements in nanofluidics. The success of the proposed project will be transformative in providing the basis for in depth studies in nanofluidics related biological transport phenomenon as well as nanofluidic devices, such as sample preconcentration and separation.
Intellectual Merit:
Interest in nanofluidics is rapidly growing as investigators begin to explore the relevant physics, chemistry and biology at the nanoscale, and the relevant nanoscale devices. Transport phenomena and velocity distribution play key roles in determining the performance of nanofluidic devices. The relevant dynamics of flow in confined geometries, such as in nano- and microfluidic devices, can be accurately described only if the physics of the flow at the interface between the fluid and the wall is thoroughly understood. One of the most important steps towards this understanding lies in determining if the flow on the solid wall is a slip or non-slip flow, and the corresponding velocity gradient at the interface. This has been a debate over the past two centuries, but a convincing conclusion is still lacking. In order to resolve unsolved questions in the nanofluidics, it is crucial to be able to accurately characterize the fluid flow velocity fields in the nanochannel. Although there has been considerable research performed in the area of nanofluidics focused on the study of velocity fields, currently only theoretical or simulation predictions exist. The reason for the lack of experimental evidence is simply that no nanovelocimeter currently exists to measure the flow velocity in nanofluidic studies. Without the capability of directly measuring the velocity field in nanofluidics, fluid dynamics models for nanochannel predictions cannot be validated.
Broader Impacts:
The novel measuring capability will have broad, cross-disciplinary impact through facilitation of efforts aimed at understanding the fundamental physics, chemistry and biology that are crucial at the nanoscale. In the area of nanofluidics, the addition to measurement science will allow scientists to probe basic nanoscale issues in areas such as the limitations and ultimate breakdown of the classical continuum description of fluid dynamics for spatially confined fluids, slip flow conditions, electrokinetics and transient flow in nanoscale. Successfulness of the project will also enhance the development and application of nanofluidics based lab-on-a-chip devices, such as electrokinetic sample preconcentration and electrophoresis for separation in nanochannels, single molecule detection. The project will also integrate research with education by incorporating research findings into curriculum development and developing low cost experimental demonstration modules, that will aid graduate, undergraduate and K-12 students in realizing the value and impact of BioMEMS devices in life science, and help foster their interest in science and engineering for their career. The project will also actively solicit students from under represented groups to take part in the research of BioMEMS.
