A multi-purpose microfluidic perfusion system with combinatorial choice of inputs, mixtures, gradient patterns, and flow rates

Abstract

Microfluidic perfusion systems, characterized by deterministic flow, low reagent consumption, small dead volumes, large integration in small footprints, high-throughput operation, and low-cost fabrication, are being increasingly used for cell culture studies in applications such as basic cell biology, molecular biological assays, tissue engineering, and systems biology. We report a multipurpose, pressure-driven and computer-controlled microfluidic perfusion device containing sixteen inlets and a large cell culture chamber. The user can choose, with sub-second temporal resolution, (a) to feed the chamber with one of 16 inlets, all 16 inlets, or one of 64 combinations of 2, 4, or 8 inlets using a binary multiplexer; (b) to introduce into the chamber a heterogeneous laminar flow of the inlets, a smoothened gradient, or a fully homogenized mixture; (c) to bypass the chamber in order to purge the inlet lines so as to minimize the dead volume; (d) to generate asymmetrical and curvilinear flow patterns within the chamber by opening side outlets; and (e) to slow down the flow by combinatorially adding segments of high fluid resistance (sixteen different levels of flow rates are possible using only four valves). All functionalities are combined to create complex gradient patterns and sequential perfusions within the central chamber.

Recent developments in microfluidic large scale integration

“…Improved designs for fundamental components include normally closed valves (NCVs) [16 ,17], structured valves [18], cell traps [19], and capacitors and diodes ( Figure 1a) [20,21]; higher-level components that have been introduced include a chamber array [22], a high performance separation column [23 ], a gradient selector (Figure 1b) [23 ], a long term gradient generator [24 ], a 2D spatial gradient controller [25], an agar filled chamber [26] and a mutilaminate mixer [27].…”

“…Likewise, valves placed in various configurations can generate temporal [24 ] or spatial control [25] over concentration gradients, while mutilaminate mixers provide fast and efficient mixing using underpass channels (Figure 1b) [27].…”

Microvalves and Micropumps for BioMEMS

“…Here the PDMS membrane is contact-transferred as a film, "sandwiched" between the control channel and the flow channel. The valve is then formed by a small pad of PDMS membrane suspended over a control channel and is positioned under the wall separating two microchannels (hence the name "doormat") [7,8,44,46]. As negative pressure is applied to the control channel, the membrane pad deflects downward and the two sides of the microchannel communicate under the wall.…”

“…This design can be fabricated entirely with SU-8 photolithography, bypassing the need for photoresist reflow and allowing for microchannels with rectangular cross-sections. PDMS-molded channels [7,44,46] and micromachined glass [8] have been used as the materials of choice for assembling doormat microvalves. Using the closed valve architecture, micromixer arrays [44], latching valves [47], and pneumatically-actuated logical structures [47,48] have been demonstrated.…”

Optical microscopy and spectroscopy of analyte-sensitive functionalized gold nanoparticles in microfluidic systems

“…This is useful for synthetic chemistry 6 , as well as in the synthesis 7,8 and functionalization of nanoparticles. In continuous flow microfluidics, where flows are laminar, control over mixing has been amply demonstrated in the form of chemical concentration gradient generators 9 , which allows for the parallelized screening of a host of different chemical compositions.…”