Basic Study of a Method for Supplying Drugs by Making Microneedles Warmed by Ultrasonic Heating

Many studies have been conducted on the application of microneedles (MNs) for drug administration in the medical field. In medical applications, large amounts of drugs need to be administered. We investigated the method of melting and diffusing a solidified regent on the punctured MN inside human skin by ultrasonic heating. This was because when the MN was punctured into human skin, the liquid did not migrate along the needle groove into the skin. As a countermeasure, the following method was adopted: after transporting liquid to the needle tip owing to capillary force, the liquid was solidified. Then the MN was punctured pseudo human skin (gel), and the solidified liquid was melted and diffused by ultrasonic heating. Temperature characteristics of the MN was investigated changing the needle material, needle diameter, and ultrasonic wave direction. In addition, the behavior of the liquid in the gel was observed under ultrasonic heating.