Bioengineering materials: Siemens innovation

Surprising Symbiosis by Siemens:

Ceramics with the microstructure of trees, nanocatalysts in bacterial proteins, nerve cells on microchips—bioengineering is set to create a surpising symbiosis of nature and technology.

Electron micrograph of a snail nerve cell. The cell is held in place on a microchip by means of plastic studs, each of which is a mere 20 µm in size

It is a remarkably delicate architecture. Three elastic strands of collagen wind around each other in loops, forming neatly stacked and networked spiral columns that incorporate hollow spaces at regular intervals. Tiny crystals of hydroxyapatite, a mineral containing calcium phosphate, are directed to the correct locations in these spaces, where they grow and fill the gaps. The result is a living ceramic substance incorporating pores and channels where cells are anchored—in essence, a bone. The structure of the substance, a combination of soft proteins and hard minerals, lends it characteristics that at first seem contradictory. Bone is hard but not brittle, rigid but flexible. It is lightweight and porous, yet can bear considerable mechanical loads. Stable and yet constantly changing, bone can even heal itself. It is truly a wonder of nature.

In recent years, researchers have been studying the principles supporting such perfectly adapted biological structures, and materials developers are now trying to put that research to practical use. Inspired by nature’s capabilities, these experts are using cells, biomolecules and biological concepts to create new materials. “Nature has optimized its matter over millions of years—we’re trying to profit from that,” says Rainer Nies, who is working on potential applications in the field of bioengineering at Siemens Corporate Technology (CT) in Erlangen, Germany.

Researchers would like to duplicate organic materials’ precise structuring, which can be measured in nanometers (one billionth of a meter). Similarly precise synthetic materials would make it possible to further miniaturize electronic and optical components and enhance their properties. For instance, Prof. Peter Greil and his team at the University of Erlangen are using biomaterials as templates for industrial materials. In one process, Greil’s team decomposes a piece of wood in a nitrogen atmosphere at about 1,800 °C, leaving behind a skeleton of pure carbon. Liquid or gaseous silicon is then pumped into the chamber, bonding with the carbon to form silicon carbide, an extremely hard compound (see image below). The key point is that the wood’s cellular structure is preserved in a kind of “petrified” image; it’s almost impossible to produce a comparably porous ceramic material using conventional methods. Such biomorphic ceramics could someday be used as catalyst carriers, filters, high-temperature insulation or construction materials