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Seminar: Klaus Mathwig (Twente)

28 Jan 2013 11:00
building 2.4w, seminar room 309b

Seminar of the PGI-8 / ICS-8:

Title: Electrical Spectroscopy in Nanofluidic Channels

Speaker: Klaus Mathwig (Nanoionics, MESA+ Institute of Technology, University of Twente)

Date: 28 January 2013 Time: 11:00

Venue: building 2.4w, seminar room 309b

In nanofluidic thin layers cells, electroactive molecules undergo redox cycling in between two closely spaced (100 nm) electrodes. This leads to a high gain of the detected faradaic current and makes the most sensitive electrochemical detection possible; even single molecules can be detected in these nanogap sensors.

Due to the Brownian motion undergone by analyte molecules, their number fluctuates considerably in a nanoscale detection volume. These mesoscopic number fluctuations contain a multiplicity of microscopic information, which is explored by techniques such as fluorescence correlation spectroscopy. Here, we introduce the equivalent electrochemical cross-correlation spectroscopy.

Moreover, using an electrical flash-release, molecules can be accumulated or depleted locally in the nanochannel. By monitoring the transient equilibration, we can conduct electrochemical transient spectroscopy to study adsorptivity and diffusivity of molecules.

We demonstrate the utility of our methods by measuring ultra-low flow rates. Liquid flow is driven through a nanochannel and molecular number fluctuations (or a concentration plug) is transported along. By employing two consecutive sensors in a single nanochannel, we can then perform a time-of-flight measurement to detect record-low flow rates below 1 pL/min.

Seminar: Klaus Mathwig (Twente)a) Nanofluidic chip. b) Top view micrograph of a nanofluidic device bonded to an additional microfluidic layer. c) Transient current response to potential step. The peaks correspond to the time of flight of the molecules along the nanochannel.

K. Mathwig., D. Mampallil, S. Kang, S. G. Lemay, Phys. Rev. Lett. 109, 118302 (2012).