Magnetization-induced self-assembly method: Micro-needle array fabrication

• A novel magnetization-induced self-assembled method (MSM) was proposed.
• The formation process of micro-needle array was analyzed and observed.
• The main effect factors on the shape of MA were investigated.

Magnetization-induced self-assembly method (MSM) was proposed to fabricate micro-needle array (MA). Curable magnetic fluid droplet array was extruded from the holes of perforated mask and meanwhile drawn to form the MA shape by magnetic force. MA was heated and cross linking solidified. The formation mechanism of magnetization-induced self-assembly micro-needle was analyzed and its process was divided into three stages: powders magnetizing, chain and aggregation, formation of micro-needle tip, and formation of micro-needle. The formation process was observed by high-speed camera. It was found that the formation process was consistent with the theoretical analysis. The effects of mask-hole diameter, powder-to-volume ratio and magnetic field intensity on MA fabrication were investigated by experiments. The results showed that the sharpness of micro-needle decreased with the decrement of mask-hole diameter and the increment of magnetic field intensity. The height of micro-needle increased with magnetic field intensity and powder-to-volume ratio. We anticipate that MSM will be suitable to fabricate MA-substrate for biomedical engineering fields such as biosensor, bio-electrode and transdermal drug delivery.

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