In-Plane, Hollow Microneedles Via Polymer Investment Molding

Abstract

Investment molding is used to create hollow, in-plane, polymer microneedles. Sacrificial investment pieces (.32 µm-diameter aluminum bond wires) are bonded into silicon micromachined molds. Needles are formed by filling these molds with Cyclic Olefin Copolymer (Ticona Topas ® ) using an injection molding machine. These needles are immersed in etchant, dissolving the investment and leaving a hollow part. Two micromachining techniques are used to make molds, RIE and KOH. The RIE molds deliver microneedles 280 µm in length with rectangular (130 µm x 100 µm) crosssections and inner diameter of ~35 µm. The KOH molds are used to create 300 µm long microneedles with 150 µm wide triangular shafts with tapered tips.

Potential of biodegradable microneedles as a transdermal delivery vehicle for lidocaine

“…As a substantial number of biodegradable microneedles are classed polymers, a supposedly third fabrication technique called investment moulding has been used suitably for hollow non-biodegradable polymers in which a drug solution flows through the hollow part of the microneedles into the skin (Lippmann 2007;Lippmann and Pisano 2006). Melt injection processes in investment moulding are suitable for thermoplastics because in adaptation of micromoulding, very high shear is required to allow for lower viscous melt and low resistant flow but heat generation can cause degradation of the drug formulation (Zhao et al 2003).…”

Polyglycolic acid microneedles modified with inkjet-deposited antifungal coatings

“…Lippmann and Pisano studied investment molding of Cyclic Olefin Copolymer (Ticona Topas V R ) to create hollow plastic microneedles. 16 Silicon molds were created with either reactive ion etching or potassium hydroxide etching. Aluminum bond wires were placed within the mold to form the sacrificial investment components.…”