Perforated support foils with pre-defined hole size, shape and arrangement

Perforated support foils with holes of pre-defined size, shape and arrangement and with hole sizes down to the sub-micrometer range, named Quantifoil, are presented. The foils are fabricated using semiconductor lithographic techniques. For the first time, a sacrificial layer that consists of a biopolymer, i.e. glutaraldehyde cross-linked gelatin, is used. This layer is removed by proteinase treatment, thus introducing an enzymatic reaction as a tool in microsystems technology. The foils are particularly beneficial in electron microscopy, when a specimen support is required with holes smaller than those attainable with metal grids (∼10 μm). Their advantages in cryo-electron microscopy, for example, are illustrated. Furthermore, foils with a specific hole size and arrangement permit a further automation of electron microscopic (EM) data acquisition procedures.