Tip fabrication methods of hollow metal microneedles

Hollow microneedles can penetrate the corneum of the skin and various biological barriers. Drugs can enter through a minimally invasive path or bodily fluid can be collected from the epidermis or dermis. This makes hollow microneedles (MN) a promising tool for drug delivery and body fluid sensing in a painless manner. Here, we propose a nickel microneedle with a length of 720 µm, an inner diameter of 27 µm, and an outer diameter of 87 µm. To construct the metal hollow microneedle model, we introduce three different manufacturing methods. The three methods are laser cutting, re-dissolution by SU-8 coating, and ultrasonic blade cutting. To verify the penetration capability, the microneedle array was tested to penetrate of the rabbit skin without rupture. The microneedle array was also repeatedly used in a film puncture experiment to verify the reliability of the structure. These microneedles can be combined with syringes and other drug delivery devices to achieve accurate quantitative and controllable flow rates of drug delivery. Through mechanical test and solution delivery test, we demonstrated that the microneedle structure has strong mechanical strength and a controllable rate of drug delivery, which is feasible as a drug delivery device.