Multifunctional microvalves control by optical illumination on nanoheaters and its application in centrifugal microfluidic devices

Abstract

Valving is critical in microfluidic systems. Among many innovative microvalves used in lab-on-a-chip applications, phase change based microvalves using paraffin wax are particularly attractive for disposable biochip applications because they are simple to implement, cost-effective and biocompatible. However, previously reported paraffin-based valves require embedded microheaters and therefore multi-step operation of many microvalves was a difficult problem. Besides, the operation time was relatively long, 2-10 s. In this paper, we report a unique phase change based microvalve for rapid and versatile operation of multiple microvalves using a single laser diode. The valve is made of nanocomposite materials in which 10 nm-sized iron oxide nanoparticles are dispersed in paraffin wax and used as nanoheaters when excited by laser irradiation. Laser light of relatively weak intensity was able to melt the paraffin wax with the embedded iron oxide nanoparticles, whereas even a very intense laser beam does not melt wax alone. The microvalves are leak-free up to 403.0 +/- 7.6 kPa and the response times to operate both normally closed and normally opened microvalves are less than 0.5 s. Furthermore, a sequential operation of multiple microvalves on a centrifugal microfluidic device using a single laser diode was demonstrated. It showed that the optical control of multiple microvalves is fast, robust, simple to operate, and requires minimal chip space and thus is well suited for fully integrated lab-on-a-chip applications.

Ionogel-based light-actuated valves for controlling liquid flow in micro-fluidic manifolds

“…In particular, valves made using photo-responsive gels are of great interest as functional materials within micro-fluidic systems since actuation can be controlled by simple light irradiation, without physical contact, offering improvements in versatility during manifold fabrication, and control of actuation [9,[14][15][16].…”

Review on miniaturized paraffin phase change actuators, valves, and pumps

“…In microvalves and dispensers, the force transmission has also been performed without an agent, i.e. by direct contact between the paraffin and a working fluid (Liu et al 2004a(Liu et al , 2004bPal et al 2004;Oh et al 2005;Yousef et al 2005;Park et al 2007;Bodén et al 2008b;Abi-Samra et al 2011;Baek et al 2013). Al-Faqheri et al (2013) used air as a force transmission agent, and used the paraffin to valve venting holes.…”

“…The most common approach to activation is through the use of resistive heaters, either integrated or positioned outside the actuator, although external activation has also been achieved through laser heating, assisted by absorbing particles in the paraffin (Park et al 2007). For some applications, e.g.…”

“…by an external gas pump (Pal et al 2004;Lin 2007, 2009), hydraulics; e.g. by the liquid flow in a channel (Liu et al 2004a), by centrifugal forces (Park et al 2007), and by an external magnet assisted by magnetic particles in the paraffin (Oh et al 2005). Latching has also been achieved with paraffin actuation alone Jonsson et al 2012).…”

“…By adding particles to paraffin, a composite material combining the thermal expansion of paraffin with electrical conductivity, e.g., for direct resistive heating (Goldschmidtböing et al 2008;Sant et al 2010), or magnetic susceptibility to enable magnetic actuation (Oh et al 2005), as well as infrared light absorption for optical activation (Park et al 2007) can be realized.…”