Drug-Delivery Micropump Relies on Body Heat

Researchers at Purdue University have developed a new type of micropump that is activated by body heat. Eventually, the researchers foresee that their technology could be used in fermentation-powered drug-delivery patches using microneedle arrays to deliver a wider range of medications than is currently possible using conventional patches.

Measuring 1.5 cm in length, the prototype microorganism-powered thermopneumatic pump is made out of layers of polydimethylsiloxane, a rubberlike polymer that is used commercially for pump diaphragms. Contained in a small chamber, the pump's secret ingredients are baker's yeast and sugar. When water is added and the patch is placed on the skin, the water and the body heat the yeast and sugar, causing them to ferment and produce carbon dioxide gas. When the gas pushes against a membrane, it can continually pump for several hours.

"This just needs yeast, sugar, water and your own body heat," remarks Babak Ziaie, a Purdue University professor of electrical and computer engineering and biomedical engineering. And because the yeast is robust, it has a long shelf life, making the pump suitable for mass production, comments, doctoral student Manuel Ochoa. In addition, the technology does not require batteries, unlike many micropumps under development or in commercial use.

"Many drugs, including those for treating cancer and autoimmune disorders, cannot be delivered with patches because they are large molecules that won't go through the skin," according to Ziaie. "Although transdermal drug delivery via microneedle arrays has long been identified as a viable and promising method for delivering large hydrophilic molecules across the skin, a suitable pump has been hard to develop." The Purdue researchers' technology could be used to push the drugs through the microneedle arrays.