Medicines sometimes must be administered in extremely small doses, sometimes just a few tenths of a milliliter. Micro-pumps, offering tiny liquid portions, have tried to do the job for a number of years, but there have always been drawbacks: most often they worked just in one direction and from a fixed pump, had bubbles form in the liquid which impaired their operation, contained too many valves or cogs, or just didn't tolerate bothersome particles.

Now, German researchers may have perfected a low-maintenance mini-pump that mimics our own throats. Indeed, the newly-developed miniature pump is so flexible tiny quantities of medicine are secreted in variable doses with extreme accuracy while going own own peristaltic system one better--moving the medicines along both backward and forward.

According to the Fraunhofer Institute for Mechanics of Materials IWM, its Freiburg-based partners from research institutes and industry have developed a "smart" controllable peristaltic pump system that resolves past drawbacks of earlier micro-pumps.

"The peristaltic pump is a highly complex system," explains IWM project manager Dr. Barbel Thielicke. "It contracts in waves in a similar way to the human esophagus, and thus propels the liquid along, (but) it changes shape of its own accord. To achieve this, we had to use a whole range of different materials and special material composites."

The Fraunhofer team used lead-zirconate-titanate (PZT) films that are joined in a suitable way with bending elements made of carbon-fiber-reinforced plastic and a flexible tube. These PZT materials change their shape as soon as an electrical field is applied, making the pump electronically controlled. Special adhesives additionally hold the various components of the pump system together.

The peristaltic pump system has passed its first functional tests; now the researchers are working to adapt their micro-pump to various medical applications.

"We work with special simulation models to do this," Dr. Thielicke adds. "We calculate in advance how the structure of the pump needs to be modified in order to administer other dosages of other liquids. This helps us save time and money during the development stage."