Experimental study on capillary flow through polymer microchannel bends for microfluidic applications

Abstract

Microchannel bends of rectangular cross-section were fabricated on polymethylmethacrylate (PMMA) by hot embossing, with a range of channel widths from 55 μm to 400 μm. The capillary movement of the interface between air and dyed water through the microchannels was recorded and analysed. The microfluidic flow behaviour as a function of the channel aspect ratio was studied. The evaluated Reynolds number was always less than 1.0 in each channel of every device. The air-water interface velocity in the devices was proportional to the channel aspect ratio. The air-water interface velocity shows a prominent increase at 90 • separation angle. We observed an increasing trend of the air-water interface velocity with increasing channel aspect ratio. We have studied the separation of 10 μm polystyrene microparticles using a simple microchannel bend structure. We have obtained approximately 100% efficiency for the combined separation and clog-free blocking of 10 μm polystyrene microparticles using the above capillary flow behaviour in a modified microchannel bend structure.

Advances in passively driven microfluidics and lab-on-chip devices: a comprehensive literature review and patent analysis

“…The effects of channel aspect ratio and different separation angles were studied for uid ow. 160 Eventually, Alphonsus et al explained in a short review on microuidic immunoassay that the capillary pressure in the channel pushed the sample, causing the uid to ow within the device. 161 Kim et al realized that the surfactant-added PDMS could be used to increase the hydrophobicity of PDMS to increase the lling rate of blood by capillary action.…”

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

“…An SU8 stamp-on-silicon-wafer was fabricated using an SF100 maskless photolithograph system (Intelligent Micro Patterning, LLC, USA) using an established SU8 processing method [ 5 , 25 , 26 ]. Briefly, SU8 50 was coated onto the silicon substrate using a spin coater at 1000 RPM to make the SU8 stamp, patterned following a soft bake by exposure to UV light at an intensity of 310 μW/cm 2 for 25 s, and developed following post-exposure bake in EC solvent for 10 min, following which the stamp was hard baked.…”

“…Briefly, SU8 50 was coated onto the silicon substrate using a spin coater at 1000 RPM to make the SU8 stamp, patterned following a soft bake by exposure to UV light at an intensity of 310 μW/cm 2 for 25 s, and developed following post-exposure bake in EC solvent for 10 min, following which the stamp was hard baked. The PMMA channels were fabricated from the stamp using a hot embossing system (EVG520, EVG Group, Austria) [ 5 - 7 , 9 ] operating at 125°C and 10 kN for 2 min. Finally, a direct bonding technique was used [ 5 , 27 ] to seal the PMMA devices to a PMMA lid.…”

“…In recent years, microfluidics has become an indispensable component of microelectromechanical systems (MEMS) technology [ 1 - 3 ], with polymer devices establishing a greater role in the development of disposable microfluidic systems [ 4 ]. One such polymer is polymethylmethacrylate (PMMA) which is used in the fabrication of a wide variety of microfluidic devices [ 4 , 5 ], from micro-reactors [ 4 ] to high aspect ratio microstructures [ 6 ], blood filters [ 7 ], and waveguide devices [ 8 ]. Additionally, PMMA microfluidic systems may be fabricated using a wide range of techniques, including injection molding, hot embossing, laser photo-ablation, and X-ray lithography [ 3 , 4 , 6 , 7 , 9 ].…”

Microchannel Thermocured Silicone Rubber

“…Washing with water leads to the formation of pores. Creation of microchannels is carried out photolithography [4], capillary force lithography [5], mould and hot embossing [6,7], sputtering on a sacrificial polymer fiber [8] and a hot roller embossing process [9]. These ways provide products with a strictly set network of microchannels.…”