Abstract
A new approach for droplet coalescence in microfluidic channels based on selective surface energy alteration is demonstrated. The proposed method involves patterning the surface of cyclic olefin copolymer (COC), a hydrophobic substrate attached to a polydimethylsiloxane hydrophobic microchannel, with graphene oxide (GO) using standard microfabrication techniques. Surface wettability and adhesion analyses confirmed the enhancement of the COC surface energy upon GO patterning and the stability of the GO film on COC. Three representative cases are illustrated to demonstrate the effectiveness of the method on the coalescence of droplets for different droplet flow regimes, as well as the effect of changing the size of the patterned surface area on the fusion process. The method achieves droplet coalescence without the need for precise synchronization.
Highlights
Coalescence of droplets in microfluidic systems offers many advantages such as high mixing rates, continuous separation of multiphase systems, and creating reaction-controlled nanoliter-sized individual reactors [1,2,3]
In the present paper we report a new approach for droplet coalescence based on selective alteration of the surface wettability of the microfluidic channel using graphene oxide (GO)
This approach involves the fabrication of a polydimethylsiloxane (PDMS) microchannel on a hydrophobic planar cyclic olefin copolymer (COC) substrate patterned with hydrophilic graphene oxide (GO) using standard microfabrication techniques
Summary
Coalescence of droplets in microfluidic systems offers many advantages such as high mixing rates, continuous separation of multiphase systems, and creating reaction-controlled nanoliter-sized individual reactors [1,2,3]. Recent studies of geometrically induced coalescence included inducing droplet coalescence in the merging zone of Y- and T-junction channels [15,16], and by introducing microgrooves [16], micropillars [17], micro-lancet [14], and by microexpansion techniques [18], and microfluidic traps [19]. In the present paper we report a new approach for droplet coalescence based on selective alteration of the surface wettability of the microfluidic channel using graphene oxide (GO) This approach involves the fabrication of a polydimethylsiloxane (PDMS) microchannel on a hydrophobic planar cyclic olefin copolymer (COC) substrate patterned with hydrophilic graphene oxide (GO) using standard microfabrication techniques
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