Professor Kristian S. Mølhave, DTU Nanolab, Technical University of Denmark

Exploring Physical, Chemical, and softmatter processes with Nanofluidic Transmission Electron Microscopy

Liquid Phase Transmission Electron Microscopy (LPTEM) has over the past twenty years opened up for atomic level imaging of processes in liquids allowing unprecedented insights into complex nanoscale processes and materials in liquids. I will illustrate our ongoing work with applications in physics, chemistry, electrochemistry, materials science, softmatter and biotechnology.

To achieve high resolution the encapsulation and liquid layer must be well controlled on the 100 nm scale. Using microfabrication methods we create novel microchip based nanochannel systems and systems clamping two chips with membranes that work as miniature laboratories in the TEM. These provide the required ultrathin liquid encapsulation, to obtain insight to complex nanoscale processes.

Combining LPTEM systems with electron holographic measurements we are beginning to explore directly mapping electric potentials and charge distributions on the nanoscale[i], which we are also beginning to probe by electrokinetic measurements. The methods also allow mapping hydration levels in softmatter.

A different nanofluidic system is the nanoscale eutectic droplets at the tip of growing nanowires at high temperature, where we use monocrystalline microcantilever heaters to control nanowire growth processes inside an Environmental TEM (ETEM) capable of providing a precursors gas atmosphere for III-V nanowire growth. By simultaneously applying electric potentials to the cantilevers we can probe how electrical fields influence the droplet and growth[ii], giving new insights to nanowire crystal phase control, surface tension and wetting angle influence.

These microchip-based systems opens up for what could be called ‘Nanofluidic Electron Microscopy’ with new capabilities in a wide range of scientific fields to probe processes in liquids with atomic scale resolution.

Speaker:

Kristian S. Mølhave is Professor in Nanotechnology Systems for In situ Electron Microscopy Applications at DTU Nanolab. He is working on developing novel microchip-based microscopy methods for high resolution imaging especially for electron microscopes in order to provide new insights into physical, chemical and biological processes on the nanoscale.