A typical application for glass capillaries supplied by Hilgenberg GmbH is found in microbiology, where they are used as “vacuum cleaners” during cell manipulation. For this purpose, their tips have miniature openings to which single cells can be attached – a procedure that has become known from the discussions about cloning.
Now, a new approach has resulted in a quantum leap regarding the reduction of the tip opening – from diameters in the micron region (10-6 m) down to the nanoscale (10-9 m). This permits glass capillaries to be produced, whose tip openings are able to capture even single molecules such as proteins or DNA. In combination with ultra-sensitive current amplifiers, this enables proteins or DNA to be detected, which permits a precise definition of length, size, and quantity of molecules that pass through the tip of the glass capillary.
This extreme reduction of the tip opening was made possible by introducing heat energy from an electron microscope into the glass, which consists mainly of silicon oxide. The process was discovered almost coincidentally by the scientist Lorenz Steinbock, when he exposed a glass capillary to an electron microscope's beam for too long. Hereby, he noticed that the diameter of the tip opening decreased continuously due to a temperature increase in the glass surface caused by the electron beam, thereby rearranging the atoms.
This nanoscale shrinkage of the tip opening under the electron microscope beam is comparable with a glass blower who shapes a workpiece by means of a flame, rotation, and the application of air pressure. In the same way that a glass blower subjects his workpiece to heat in a controlled manner, the intensity of the electron beam can be controlled and stopped as soon as the nanoscale tip opening reaches the required diameter.
Thanks to this discovery, the application range for Hilgenberg glass capillaries has been increased significantly.