Eric Jensen

In-situ SEM microchip setup for electrochemical experiments with water based solutions.

Studying electrochemical (EC) processes with electron microscopes offers the possibility of achieving much higher resolution imaging of nanoscale processes in real time than with optical microscopes. We have developed a vacuum sealed liquid sample electrochemical cell with electron transparent windows, microelectrodes and an electrochemical reference electrode. The system, called the EC-SEM Cell, is used to study electrochemical reactions in liquid with a standard scanning electron microscope (SEM). The central component is a microfabricated chip with a thin (50 nm) Si-rich silicon nitride (SiNx) window with lithographically defined platinum microelectrodes. We show here the design principles of the EC-SEM system, its detailed construction and how it has been used to perform a range of EC experiments, two of which are presented here. It is shown that the EC-SEM Cell can survive extended in-situ EC experiments. Before the EC experiments we characterized the beam current being deposited in the liquid as this will affect the experiments. The first EC experiment shows the influence of the electron-beam (e-beam) on a nickel solution by inducing electroless nickel deposition on the window when increasing the current density from the e-beam. The second experiment shows electrolysis in EC-SEM Cell, induced by the built-in electrodes.

Monolithic Chip System with a Microfluidic Channel for In Situ Electron Microscopy of Liquids

Electron microscopy of enclosed liquid samples requires the thinnest possible membranes as enclosing windows as well as nanoscale liquid sample thickness to achieve the best possible resolution. Today liquid sample systems for transmission electron microscopy (TEM) are typically made from two sandwiched microchips with thin membranes. We report on a new microfabricated chip system based on a monolithic design that enables membrane geometry on the scale of a few micrometers. The design is intended to reduce membrane deflection when the system is under pressure, a microfluidic channel for improved flow geometry, and a better space angle for auxiliary detectors such as energy-dispersive X-ray spectroscopy. We explain the system design and fabrication and show the first successful TEM images of liquid samples in the chips.

Optofluidic microscope with 3D spatial resolution

This paper reports on-chip based optical detection with three-dimensional spatial resolution by integration of an optofluidic microscope (OFM) in a microfluidic pinched flow fractionation (PFF) separation device. This setup also enables on-chip particle image velocimetry (PIV). The position in the plane perpendicular to the flow direction and the velocity along the flow direction of separated fluorescent labeled polystyrene microspheres with diameters of 1 microm , 2.1 microm , 3 microm and 4 microm is determined by the OFM. These results are bench marked against those obtained with a PFF device using conventional fluorescence microscope readout. The size separated microspheres are detected by OFM with an accuracy of <or=0.92 microm . The position in the height of the channel and the velocity of the separated microspheres are detected with an accuracy of 1.4 microm and 0.08 mm/s respectively. Throughout the measurements of the height and velocity distribution, the microspheres are observed to move towards the center of the channel in regard to its height.

Revealing the Working Active Sites of M1 phase for Ethane Oxidation

1. Physical & Computational Sciences Directorate, Pacific Northwest National Laboratory, Richland, WA 99352, USA 2. Environmental Molecular Sciences Laboratory and Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, WA 99352, USA 3. Department of Chemistry and Catalysis Research Center, Technical University of Munich, Garching 85748, Germany 4. Department of Materials Science and Engineering, University of Washington, Seattle, WA 98195, USA

Three-dimensional positioning with optofluidic microscope

This paper reports on-chip based optical detection with three-dimensional spatial resolution by integration of an optofluidic microscope (OFM) in a microfluidic pinched flow fractionation (PFF) separation device. This setup also enables on-chip particle image velocimetry (PIV). The position in the plane perpendicular to the flow direction and the velocity along the flow direction of separated fluorescent labeled polystyrene microspheres with diameters of 1 μm, 2.1 μm, 3 μm and 4μm is measured using the OFM readout. These results are bench marked against those obtained with a PFF device using a conventional fluorescence microscope as readout. The size separated microspheres are detected by OFM with an accuracy of ≤ 0.92μm. The position in the height of the channel and the velocity of the separated microspheres are detected with an accuracy of 1.4 μm and 0.08mm/s respectively. Throughout the measurements of the height and velocity distribution, the microspheres are observed to move towards the center of the channel in regard to its height.