Skin patches may well replace needles and syringes for most medical injections, but scientists are still working to create the ideal alternative that balances the desire for a flexible, comfortable-to-wear patch with an effective needle that penetrates the skin.

Researchers at the KTH Royal Institute of Technology in Stockholm, Sweden, think they may have solved the problem by embedding an array of stainless steel microneedles in a polymer patch.

KTH patch combines a flexible polymer base with stainless steel needles. KTH patch combines a flexible polymer base with stainless steel needles. The soft, flexible material makes it comfortable to wear, while the stiff needles ensure reliable skin penetration. Researchers say they believe it’s the first patch of its type to be scientifically studied.

Unlike epidermal patches, microneedles penetrate the upper layer of the skin, just enough to avoid touching the nerves, but far enough to deliver drugs. Beside drug delivery, the patch also could be used to extract physiological signals for fitness monitoring devices, extract body fluids for real-time monitoring of glucose, pH level and other diagnostic markers, as well as for bioelectric and cosmetic skin treatments, researchers say.

Most microneedle arrays being tested today are “monoliths,” says Frank Niklaus, professor of micro and nanofabrication at KTH. That means that the needles and their supporting base are made of the same, often stiff and uncomfortable material. On the other hand, patches made completely of softer material use needles that are less reliable for penetrating the skin.

“To the best of our knowledge, flexible and stretchable patches with arrays of sharp and stiff microneedles have not been demonstrated to date,” he says.

KTH researchers tested two variations of their concept. One was stretchable and slightly more flexible than the other. The more flexible patch had a base of molded thiol-ene-epoxy-based thermoset film, and conformed well to deformations of the skin surface. Each of the 50 needles penetrated the skin during a 30-minute test.

This type of microneedle patch could have implications for healthcare delivery, says co-researcher Niclas Roxhed, research leader at the KTH Department of Micro and Nano Systems. Notably, he says, those with chronic conditions would no longer have to endure the discomfort of daily injections. More broadly, the risk of spreading infections through improper handling of needles would be reduced since the patch does not enter the bloodstream.