Out-of-plane microtube arrays for drug delivery—liquid flow properties and an application to the nerve block test

We have proposed fabricating very fine out-of-plane silicon-dioxide microtube arrays using a selective vapor–liquid–solid (VLS) growth technique and microfabrication processes. In this study, we elucidated the liquid-flow properties of microtubes with different inner diameters. Our fabricated microtubes were 0.5 μm in wall thickness; 20 μm in height; and either 2.5 μm, 4.1 μm, 4.6 μm, or 6.4 μm in inner diameter. We determined the relationship between the flow pressure and the liquid flow rate through the microtube. We also conducted a nerve block test, in which a microtube with 4.6 μm inner diameter was used to administer lidocaine solution (Na channel blocker) to the rat sciatic nerve. This successful test represents the first reported use of a microtube for drug delivery to the peripheral nerve of a rat. We conclude that the proposed microtube array and its fabrication process might contribute to developing pharmacological devices.