Porous Membranes

The investigation of matter on the nanoscale has been revolutionised by new imaging techniques such as Atomic Force Microscopy and Scanning Tunneling Microscopy. It is often said that the field of nano-technology was born with the invention of Scanning Tunneling Microscopy in the early 1980s. In this proposal we apply a completely new imaging technique, the scanning helium atom microscope, in the investigation of materials. In the scanning helium atom microscope a focused beam of neutral helium atoms is used as a probe to investigate materials. The two major advantages are the low energy of the helium beam (less than 100 meV) for a wavelength of 1 Å) and the fact that the atoms are uncharged. We propose to apply the helium microscopy technique to the investigation of: a) Artificial membranes. By focussing the helium beam onto the membrane and measuring the transmitted signal the local transmissivity (permeability) of the membranes can be determined, thus yielding information about the internal structure. This information will be used to improve the models for membrane creation and eventually tune the membrane properties for applications. No technique currently available can provide this information. b) Biological membranes. With the focused helium beam used in diffraction mode, structural information of fragile protein crystals will be obtained. Fragile protein crystals are easily damaged when investigated with standard diffraction techniques, which limits the resolution. Case-Study measurements will be carried out in transmission mode on 2D S-layer protein crystals (S-layer proteins are present in, among others, bacteria membranes).

The investigation of matter on the nanoscale has been revolutionised by new imaging techniques such as Atomic Force Microscopy and Scanning Tunneling Microscopy. It is often said that the field of nano-technology was born with the invention of Scanning Tunneling Microscopy in the early 1980s. In this proposal we apply a completely new imaging technique, the scanning helium atom microscope, in the investigation of materials. In the scanning helium atom microscope a focused beam of neutral helium atoms is used as a probe to investigate materials. The two major advantages are the low energy of the helium beam (less than 100 meV) for a wavelength of 1 Å) and the fact that the atoms are uncharged. We propose to apply the helium microscopy technique to the investigation of: 1. Artificial membranes. By focussing the helium beam onto the membrane and measuring the transmitted signal the local transmissivity (permeability) of the membranes can be determined, thus yielding information about the internal structure. This information will be used to improve the models for membrane creation and eventually tune the membrane properties for applications. No technique currently available can provide this information. 2. Biological membranes. With the focused helium beam used in diffraction mode, structural information of fragile protein crystals will be obtained. Fragile protein crystals are easily damaged when investigated with standard diffraction techniques, which limits the resolution. Case-Study measurements will be carried out in transmission mode on 2D S-layer protein crystals (S-layer proteins are present in, among others, bacteria membranes).