Geometrical strengthening and tip-sharpening of a microneedle array fabricated by X-ray lithography

Abstract

A novel fabrication method for LIGA (from the German ''Lithographie'', ''Galvanik'', and ''Abformung'') microneedles with through holes is presented. Such microneedles are in demand by most bio-medical MEMS applications and in some fluidic MEMS applications. We propose a technique that combines conventional deep X-ray lithography, plane-pattern to cross-section transfer (PCT) process, and alignment Xray lithography. The technique provides precise hole alignment with ± 3 lm tolerance. Finite-element simulations on various hole locations were performed to determine the optimum position. We previously fabricated a microneedle with a 100-lm base and a 300-lm height by a right-triangular mask. The resultant microneedle had a very sharp tip but was excessively steep, and thus resulted in a very low strength. Improved strength and tip sharpness was consequently achieved by changing the mask-pattern from a triangular pattern to a polygonal mask and changing the dimensions of the microneedle to have a 300-lm base with various heights between 350 and 800 lm. Using the proposed technique, we could produce a total of 100 hollow microneedles on a 5 · 5 mm 2 chip. Moreover, we successfully fabricated sharpened microneedles that were stronger than that we have fabricated so far. The molding process or electroplating and the cost list of the LIGA microneedle will also be included.

Optimization of square microneedle arrays for increasing drug permeability in skin

“…The Schematic diagram of solid and hollow microneedles. (2005) d. Teo et al (2005) e. Xie et al (2005) f. Wu et al (2007) g. Khumpuang et al (2007) h. Verbaan et al (2007) Optimization Function, g (-)…”

“…They conclude that the square mask shape has the optimum shape compared to other shapes (e.g., diamond and circular). Khumpuang et al (2007) have considered the optimum locations for various microneedle holes. The microneedle tip 100 radius has been optimized to improve the tip sharpness by Teo et al (2006).…”

Blood-mimicking delivery in polygonal structure of inner quadrupletip microneedle with valveless micro-pump

“…Needles are defined as sharp hypodermic needle that has a function to be painless while completing the task of penetrating the human outermost skin to withdraw blood or injecting fluid into the blood stream [1]~ [4]. The advancement of the research leads to the technologies of micro-needles in improving the flow and performance which includes attaching micropump at the microneedle [5]. While keeping microneedle in a longer length, the design parameters of the microchannels differ in order to obtain higher velocity.…”

Micro-Needle with Polygonal Structure of Micro-Channel for Stress and Blood or Drug Flow Optimization

“…Needles are defined as sharp hypodermic needle that has a function to be painless while completing the task of penetrating the human outermost skin to withdraw blood or injecting fluid into the blood stream [1][2][3][4]. From hypodermic needles to the current conventional micro-needle, the advancement of the researches leads to the technologies of microneedles in improving the flow and performance while completing the task of penetrating the human outermost skin [5]. In general, micro-channels are regarded as an effective method for the field of heat transfer in the application of various fluids and fluid velocity [6].…”

“…From hypodermic needle, the advancement of the researches leads to the technologies of micro-needles with the efforts to bypass the stratum corneum that enhance drug penetration. Penetrations up to 1.5mm are considered to be painless [12]. Sharper tip of needle ease the penetration process as the generated stress is only little compared to the blunt tip.…”