Fraunhofer Institute for Biomedical Engineering
Trajectories of fluorescing nanobeads above interdigitated electrodes at a field frequency of 500 MHz. Superposition of 180 images, frame rate 0.5 Hz, false colour representation.
© Fraunhofer IBMT.
In electronics as well as chemical analytics there is a continuous development towards smaller devices. The geometrical dimensions of the smallest subunits are approaching molecular dimensions. Accordingly, conventional manufacturing methods being based on e. g. light reach their principal physical limits. A possible solution for this is the "bottom-up approach" in which such units are constructed from single molecules. Such syntheses happen in living cells at any time. Chemical compounds as well as complex structures are built that are quite similar to the envisages technical systems: chemical, mechanical and electrical sensors, transport and processing of matter and information, and actuators that act again in a chemical, mechanical or electrical way.
The Biomolecular Nanostructures Group is exploiting the ability of biological macromolecules to self-organize in order to manufacture nanometer sized objects "in the tube". Most promising are DNA and proteins since there exists a multiplicity of standard laboratory tools and methods for their synthesis, manipulation and characterization.
DNA is the carrier of genetic information, however, here it is used as a systematically constructed scaffold with a narrowly defined repeating pattern of 0.34 nm, which is the natural distance between adjacent base pairs in the DNA doublestrand. Characterization of the prepared nanostructures is performed by electrical, mechanical and optical means. Nano- and microelectrodes allow for concentration, alignment and temporal immobilization of the structures. By optical, especially fluorescence microscopy single molecules can be observed with nearly real time temporal resolution, still with a spatial resolution not below 200 nm. Better spatial resolution down to single molecules can be achieved by atomic force scanning microscopy, however, at the expense of temporal resolution.
An aim of the actual work is the construction of a sensor that is capable to detect a few molecules of just a single cell.