Nanoscale surface modifications to control capillary flow characteristics in PMMA microfluidic devices

Abstract

Polymethylmethacrylate (PMMA) microfluidic devices have been fabricated using a hot embossing technique to incorporate micro-pillar features on the bottom wall of the device which when combined with either a plasma treatment or the coating of a diamond-like carbon (DLC) film presents a range of surface modification profiles. Experimental results presented in detail the surface modifications in the form of distinct changes in the static water contact angle across a range from 44.3 to 81.2 when compared to pristine PMMA surfaces. Additionally, capillary flow of water (dyed to aid visualization) through the microfluidic devices was recorded and analyzed to provide comparison data between filling time of a microfluidic chamber and surface modification characteristics, including the effects of surface energy and surface roughness on the microfluidic flow. We have experimentally demonstrated that fluid flow and thus filling time for the microfluidic device was significantly faster for the device with surface modifications that resulted in a lower static contact angle, and also that the incorporation of micro-pillars into a fluidic device increases the filling time when compared to comparative devices.

Self-Powered Triboelectric Nanosensor for Microfluidics and Cavity-Confined Solution Chemistry

“…To correct the difference between the results obtained in those two approaches, we introduce the coefficient of channel resistance f c and the cross section area S of the microchannel in a relationship between v f and V pump as given by The fluid flowing in microchannels is quite different from that in macrochannels. As the surface roughness and the dimensions of microchannel have great impact on the flow dynamics; there are many factors that will determine the channel resistance ( f ) in microchannels. , How to measure and compare the channel resistance in different microchannels is an important issue in related research application. Microchannels with a rectangular cross section are designed for the measurement and comparison (Figure S2); is the length of the cross section is b and the width is a , the equivalent diameter d e of microchannel with rectangular cross section is The relationship between the volume flow rate V pump and the in situ flow velocity ( v f ) in microchannel is Here f c is the channel resistance coefficient caused by the liquid passing the microchannel with different cross section area ( S = a × b ).…”

“…As the surface roughness and the dimensions of microchannel have great impact on the flow dynamics; there are many factors that will determine the channel resistance (f) in microchannels. 36,37 How to measure and compare the channel resistance in different microchannels is an important issue in related research application. Microchannels with a rectangular cross section are designed for the measurement and comparison (Figure S2); is the length of the cross section is b and the width is a, the equivalent diameter d e of microchannel with rectangular cross section is…”

Surface modification of polymers by reduction of diazonium salts: polymethylmethacrylate as an example

“…Surface modication of PMMA has been achieved mainly by plasma irradiation. Atmospheric pressure air 26,27 and oxygen [28][29][30][31] discharge plasma increase the surface oxygen-containing polar groups such as alcohols, ketones, carboxylic acids and the hydrophylicity of the surface, 29 these groups permit further functionalization with, for example, streptavidin. 28 2-Hydroxyethylmethacrylate (HEMA) was immobilized on PMMA intraocular lens by dielectric barrier discharge plasma; hydrophilicity of the samples was signicantly and permanently improved.…”

Diamond materials for microfluidic devices

“…PMMA microchannels with a micropillar array structure and modifi ed channel surfaces with DLC coatings are presented in Mukhopadhyay et al (2011). This study investigated the effects of surface modifi cations such as changes in surface energy and surface chemistry.…”