Hydrogel composition effects on microchannel formation using a direct-deposition hydrogel molding process for microfluidic devices fabrication

摘要

Introduction: Microfluidic devices are widely used in biomedical applications because of their inherent advantages[1]. It is known that microfluidic devices are often manufactured using microfabrication processes, which require specialized equipment; researchers are developing alternative microfabrication-free techniques. One of the developed techniques is hydrogel molding method (HGM). This paper presents a direct-deposition HGM-based fabrication process for producing microchannels without using microfabrication techniques. The objective of this study is to examine effects of hydrogel composition on microchannel formation and workability at room temperature. Materials and Methods: Agarose (Sigma-Aldrich) and glycerin aqueous solutions were used to generate channels. Three compositions examined were (a) 2% w/v agarose and 16% v/v glycerin, (b) 4% w/v agarose and 16% v/v glycerin, and (c) 4% w/v agarose and 8% v/v glycerin. The base material was PDMS (polydimethylsiloxane) (SYLGARD184, Dow Coming). The fabrication process consisted of: (1) pour PDMS into a mold; (2) place PDMS in vacuum for 20 minutes and then cure at 60 °C for one hour to form a base layer; (3) direct-deposit hydrogel as a filament on to the base-layer using blunt-tip dispensing-needles to form microchannel; (4) pour top layer of PDMS over the channel molds; (5) place in vacuum for 20 minutes and then cure at room temperature for 24 hours; (6) pneumatically flush out hydrogel after reheating. 20,22, and 25 gauge needles were used to control the filament diameter. A microscope coupled with a DinoCapture 2.0 was used to image the formed micro channels. Cross-section diameter and its variation along the channel direction were examined. Two approaches for integrating inlets and outlets (10mm long and1/32" ID silicon tubes) to the devices were also examined: (ⅰ) deposit extra hydrogel at the inlet and outlet positions during Step (3), insert silicon tubes after Step (6), then seal the connection with PDMS; (ⅱ) place the silicon tubes in place vertically and deposit hydrogel support around tubes during Step (3) with no additional sealing. Flow tests were conducted to determine the functionality of the inlets and outlets. Results: Table 1 displays the effects of hydrogel composition on channel diameter. Figure 1 compares the variation of channel diameter along the channel direction for composition (b). Table 2 compares the average diameter and standard deviation for various deposition-needle gauges. The results show that the process produces microchannels of good precision. It was also observed that compositions (b) and (c) had good workability during deposition, while (a) melted easily at room temperature. Figure 2 shows a simple device fabricated using the second integration method, however, producing more complex channels is possible. Figure 1: Channel diameter along the channel direction for composition (b) Figure 2: Example device fabricated using outlined process Conclusion and Future Work: In this study, we examined the hydrogel composition effects on microchannel formation using direct-deposition HGM. Results suggest that the method is an inexpensive, rapid and flexible method for generating microchannels. Implementing a precision x-y stage is in progress to allow for producing complex channels; and a wider range of hydrogel composition will be studied to optimize workability at room temperature.