Optothermally actuated capillary burst valve

Abstract

We demonstrate the optothermal actuation of individual capillary burst valves in an all-polymer microfluidic device. The capillary burst valves are realised in a planar design by introducing a fluidic constriction in a microfluidic channel of constant depth. We show that a capillary burst valve can be burst by raising the temperature due to the temperature dependence of the fluid surface tension. We address individual valves by using a local heating platform based on a thin film of near infrared absorber dye embedded in the lid used to seal the microfluidic device [L. H. Thamdrup et al., Nano Lett. 10, 826–832 (2010)]. An individual valve is burst by focusing the laser in its vicinity. We demonstrate the capture of single polystyrene 7 μm beads in the constriction triggered by the bursting of the valve.

A Review of Capillary Pressure Control Valves in Microfluidics

“…Due to the interrelationship between fluid surface tension and temperature, increasing the temperature can make the CPCV meniscus rupture. Johan Eriksen et al embedded the near-infrared absorption dye film into a sealed microfluidic device and used laser local heating to open a single valve [135], shown in Figure 5C.…”

“…Reprinted with permission from [134]. (C) The laser drive is used to capture particles.Reprinted with permission from[135]. Copyright 2017 American Institute of Physics.…”

Capillary stop valve actuation by thermo-pneumatic- pressure for lab-on-chip systems

“…For resumption of flow, a suitable actuation mechanism of the stop valve is required which would breach the capillary barrier of the structure (Irimia 2008). Several novel methods have been successfully employed to do this like pressure from bubble generated by electrolysis reported by Man et al 1998, by lowering the surface tension opto-thermally by using a laser directed at the valve meniscus demonstrated by Eriksen et al 2017 or by means of centrifugal force as described in Cho et al 2007 etc. We adopt thermo-pneumatic pressure in this paper for the actuation of capillary stop valve. Some earlier works have already been done on thermo-pneumatic principle.…”