An integrated channel selector system employing thermoreversible gelation of a polymer was developed. Here, we show a system with arrayed microchannels having nine crossing points. Infrared laser irradiation was used to form gel areas at several crossing points in arranging a flow path from the inlet to one of the nine outlets passing through certain junctions and channels. The multipoint irradiation by the infrared laser was realized using a personal-computer-controlled digital mirror device. The system was demonstrated to be able to direct flow to all nine outlets. Finally, we achieved to produce flexible paths for flowing particles including side trips. 1. Introduction Microfluidic technologies are recognized as powerful tools in many fields such as chemistry, biology, and medicine [1–3]. These technologies make it possible, for example, to analyze a tiny amount of samples and allow the development of quite-homogeneous reactor systems called microprocess servers. In the microfluidic systems that have been developed, fluids are usually moved in one direction through prebuilt channels, which provide only limited flexibility. To increase flexibility and complexity in changing flow direction, numerous valve systems controlled by various forces have been developed, for example, a pneumatically controlled valve constructed of soft material, miniaturized mechanical valves fabricated using micromachining technologies, and regulation of flow resistance changes in a microchannel employing pH-sensitive or temperature-sensitive gelation or light-driven wettability changes [4–12]. Among these valves, the pneumatically controlled valve has been applied in many types of devices because of its simplicity of fabrication and the possibility of multiple-valve manipulation [4, 7]. However, the operation of the pneumatic valve is controlled by an off-chip solenoid valve, and the large-scale integration of microvalves requires the same numbers of off-chip control solenoid valves and world-to-chip connectors [13]. We have developed flow control systems that have one input and two to five outputs thermoreversible gelation of hydrogel with infrared (IR) laser-induced local heating [14–16]. We succeeded to direct the flow selectively in a noncontact way, but the techniques based on the flow switching at only one junction. Here, we extend the flow control mechanism to the flow control on a flexible pathway junction with independently regulated 18 valves. 2. Materials and Methods 2.1. Structure of a Microchannel Matrix We designed an integrated channel selector as a matrix of
References
[1]
C. Aoyama, A. Saeki, M. Noguchi et al., “Use of folded micromachined pillar array column with low-dispersion turns for pressure-driven liquid chromatography,” Analytical Chemistry, vol. 82, no. 4, pp. 1420–1426, 2010.
[2]
Y. Xu, K. Jang, T. Yamashita, Y. Tanaka, K. Mawatari, and T. Kitamori, “Microchip-based cellular biochemical systems for practical applications and fundamental research: from microfluidics to nanofluidics,” Analytical and Bioanalytical Chemistry, vol. 402, pp. 99–107, 2012.
[3]
Y. Song, M. Noguchi, K. Takatsuki et al., “Integration of pillar array columns into a gradient elution system for pressure-driven liquid chromatography,” Analytical Chemistry, vol. 84, pp. 4739–4745, 2012.
[4]
I. E. Araci and S. R. Quake, “Microfluidic very large scale integration (mVLSI) with integrated micromechanical valves,” Lab on a Chip, vol. 12, pp. 2803–2806, 2012.
[5]
T. Arakawa, T. Sameshima, Y. Sato et al., “Rapid multi-reagents exchange TIRFM microfluidic system for single biomolecular imaging,” Sensors and Actuators B, vol. 128, no. 1, pp. 218–225, 2007.
[6]
G. Chen, F. Svec, and D. R. Knapp, “Light-actuated high pressure-resisting microvalve for on-chip flow control based on thermo-responsive nanostructured polymer,” Lab on a Chip, vol. 8, no. 7, pp. 1198–1204, 2008.
[7]
J. W. Hong and S. R. Quake, “Integrated nanoliter systems,” Nature Biotechnology, vol. 21, no. 10, pp. 1179–1183, 2003.
[8]
M. Krishnan and D. Erickson, “Optically induced microfluidic reconfiguration,” Lab on a Chip, vol. 12, pp. 613–621, 2012.
[9]
M. Krishnan, J. Park, and D. Erickson, “Optothermorheological flow manipulation,” Optics Letters, vol. 34, no. 13, pp. 1976–1978, 2009.
[10]
D. S. Reichmuth, T. J. Shepodd, and B. J. Kirby, “On-chip high-pressure picoliter injector for pressure-driven flow through porous media,” Analytical Chemistry, vol. 76, no. 17, pp. 5063–5068, 2004.
[11]
B. Stoeber, C. M. J. Hu, D. Liepmann, and S. J. Muller, “Passive flow control in microdevices using thermally responsive polymer solutions,” Physics of Fluids, vol. 18, no. 5, Article ID 053103, 2006.
[12]
G. Takei, M. Nonogi, A. Hibara, T. Kitamori, and H. B. Kim, “Tuning microchannel wettability and fabrication of multiple-step Laplace valves,” Lab on a Chip, vol. 7, no. 5, pp. 596–602, 2007.
[13]
S. Shoji and K. Kawai, “Flow control methods and devices in micrometer scale channels,” Topics in Current Chemistry, vol. 304, pp. 1–25, 2011.
[14]
H. Sugino, K. Ozaki, Y. Shirasaki, T. Arakawa, S. Shoji, and T. Funatsu, “On-chip microfluidic sorting with fluorescence spectrum detection and multiway separation,” Lab on a Chip, vol. 9, no. 9, pp. 1254–1260, 2009.
[15]
Y. Shirasaki, J. Tanaka, H. Makazu et al., “On-chip cell sorting system using laser-induced heating of a thermoreversible gelation polymer to control flow,” Analytical Chemistry, vol. 78, no. 3, pp. 695–701, 2006.
[16]
H. Sugino, T. Arakawa, Y. Nara et al., “Integration in a multilayer microfluidic chip of 8 parallel cell sorters with flow control by sol-gel transition of thermoreversible gelation polymer,” Lab on a Chip, vol. 10, no. 19, pp. 2559–2565, 2010.
[17]
S. Y. Lee, Y. Lee, J. E. Kim, T. G. Park, and C. H. Ahn, “A novel pH-sensitive PEG-PPG-PEG copolymer displaying a closed-loop sol-gel-sol transition,” Journal of Materials Chemistry, vol. 19, no. 43, pp. 8198–8201, 2009.
