Abstract
In this paper we present various pneumatically actuated microfluidic valves to enable user-defined fluid management within a microfluidic chip. To identify a feasible valve design, certain valve concepts are simulated in ANSYS to investigate the pressure dependent opening and closing characteristics of each design. The results are verified in a series of tests. Both the microfluidic layer and the pneumatic layer are realized by means of soft-lithographic techniques. In this way, a network of channels is fabricated in photoresist as a molding master. By casting these masters with PDMS (polydimethylsiloxane) we get polymeric replicas containing the channel network. After a plasma-enhanced bonding process, the two layers are irreversibly bonded to each other. The bonding is tight for pressures up to 2 bar. The valves are integrated into a microfluidic cell handling system that is designed to manipulate cells in the presence of a liquid reagent (e.g. PEG – polyethylene glycol, for cell fusion). For this purpose a user-defined fluid management system is developed. The first test series with human cell lines show that the microfluidic chip is suitable for accumulating cells within a reaction chamber, where they can be flushed by a liquid medium.
Highlights
The integration of new characteristics into a cellular system is an essential challenge in modern biotechnology
With about 15 μm in the central region of the valve the opened cross-section of this valve type is clearly smaller than the channel itself, as can be seen in the ANSYS simulations (Fig. 10, 11)
In the test series with human cell lines U937 and L540 we showed that the microfluidic chip is suitable for user-defined cell handling
Summary
The integration of new characteristics into a cellular system is an essential challenge in modern biotechnology. Fusion is traditionally performed in a cell bulk of two mixed cell lines The drawback of this traditional type of cell fusion within a bulk is the statistical combination of the cells. The use of microfluidic systems has become an eligible method for applications like biochemical assays, medical diagnostics, drug delivery, cell sorting and cell manipulation, as they enable transportation, isolation and manipulation of small amounts of liquids and cells or even single cells. This microfluidic system enables the user to select certain cells which should be manipulated or investigated. Polydimethylsiloxane (PDMS) is a well suited material for these applications, as microfluidic systems can be developed very cheaply and rapidly by methods of soft lithography [1, 2]
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