Integration of movable structures in PDMS microfluidic channels

Abstract

In this paper, we analyzed the behavior of moving structures in a check valve micropumping system and proposed a method to improve the freedom of motion of such structures. A model ball valve in a microchannel system was designed for this study. The behavior of the glass sphere, which acted as an independent flow check valve in the PDMS microfluidic channel, was analyzed. We found that the motion of the ball valve in the microchannel was sensitive to the properties of the interface between the ball, channel, and liquid. The glass ball valve moved freely when methanol or ethanol was introduced into the PDMS channel. However, the ball valve adhered to the PDMS channel when deionized (DI) water or cell culture media was introduced. Such behavior inhibits the applicability of this micropump to biological systems. The adhesion properties were modeled using the theory of interfacial actions between heterogeneous materials. The theoretical model successfully predicted the interaction properties that governed ball valve motion in the PDMS microchannels. To ameliorate the excessive adhesion in DI water or cell culture media, a hybrid inorganic/organic polymer (HR4) was used to coat the PDMS channel. In the HR4-coated ball valve micropump, the glass ball moved freely in DI water and cell culture media. Finally, the biocompatibility of the HR4 coating was evaluated by pumping human mesenchymal stem cells (hMSCs) suspended in media, and the pumped cells were cultured and evaluated for viability. A good viability demonstrated that the HR4 pump was biocompatible.

On importance of surface forces in a microfluidic fluidized bed

“…1. The free energies obtained from the combinations for a triplet were then used to obtain the averages and standard deviations shown in All calculations but one predict glass microparticles will be attracted to a PDMS wall when immersed in water; only when the PDMS parameters of Hu et al (2010) are used with the glass parameters of van Oss (2008) do we get a positive free energy (ΔG 1w2 = 5.12 mJ/m 2 ) indicating repulsion between the two materials in the presence of water.…”

Functionality integration in stereolithography 3D printed microfluidics using a “print-pause-print” strategy

“…Passive valves are also part of the classical fluidic toolbox, especially check valves (or diodes) that allow the flow only in an open direction, and block the flow from a close direction. [39][40][41] Here, we propose to reproduce a design from Morgan et al where a stainless steel ball can be pushed against a silicone O-ring to block the flow (close direction), or sent in a larger channel by a flow in the opposite, open direction (see Fig. 6c).…”

Silicone rubber films modified by ethylenoxy moieties: Characterization and drug delivery properties

“…Materials based on silicone rubber (SR) elastomers [e.g., crosslinked poly(dimethylsiloxanes) (PDMS)], because of their attractive properties of biocompatibility,1, 2 good mechanical and thermal properties and chemical inertness, have drawn significant interest over the past years since they can be used in numerous applications. Relevant examples involve tissue engineering,3 bioelectrodes,4 microfluidic5, 6 as well as various medical devices,7–9 contact lenses10 and drug delivery systems 11–17. Although advantageous in many areas, PDMS is by nature an inherently hydrophobic material which limits markedly its range of applications.…”