Drugs can be delivered into the body using a variety of different routes (1,2). The oral route is generally most popular, due largely to convenience for the patient. However, many drugs are degraded in the gastrointestinal tract or by ﬁrst-pass effects of the liver or are simply not absorbed across the intestinal epithelium. The usual alternative is delivery across the skin, typically using a hypodermic needle. Although the needle is highly effective to deliver drugs, it is often inconvenient and painful for patients.