Microwave in Microfluidics

Microwave in microfluidics studies the interaction of microwaves with materials involved in microfluidics and the effective method for controlling microwave power with an ultimate goal of developing microwave systems and components that can add functionalities to microfluidic platforms. 

Moschou et al. used the compact disc microfluidic platform that is spun to allow the centripetal force to achieve pumping of the mobile phase through the channel. They incorporated a poly(2-hydroxyethyl methacrylate-co-ethylene dimethacrylate-co-[2-(methacryloyloxy) ethyl] trimethylammonium chloride) monolith in the channel of a poly(dimethylsiloxane) (PDMS) chip. The unusual feature of this preparation is the use of irradiation with microwaves in a common domestic microwave oven to initiate the polymerization reaction, which is then completed in only 4.5 min. This is a significantly shorter time compared to 20 h required to obtain monolith using thermally initiated polymerization of the same mixture. This monolith was then used for the purification of enhanced green fluorescent protein in ion-exchange mode. 

Issadore D, Humphry KJ, Brown KA, Sandberg L, Weitz DA, Westervelt RM (2009) Microwave dielee-tric heating of drops in microfluidic devices. Lab Chip 9(12) 1701-1706... 

Coplanar waveguide structures are used for transmission line-based sensing methods. Booth et al. used the coplanar waveguide structure between the microfluidic channel and the quartz substrate. The microfluidic channel and the transmission line are aligned so that the microwave power propagation and the fluid flow directirui are orthogruial as shown in Fig. 8. As a result, the microwave power experiences three types of transmissirui fines ... 

In Ref. [6], the complex permittivity of PDMS is also measured which is an important data for engineers in developing microwave components for microfluidic platforms. The complex permittivity of PDMS is fitted to the Cole-Cole function... 

Shah JJ, Sunderesan SG, Geist J, Reyes DR, Booth JC, Rao MV, Gaitan M (2007) Microwave dielectrie heating of fluids in an integrated microfluidic device. J Micromech Microeng 17(11) 2224—2230... 

Recently, the synthesis of crystalline tungsten oxide nanoparticles within benzyl alcohol droplets was achieved by using microwave dielectric heating of non-aqueous droplets in a microfluidic device with a reaction time of just 64 ms [112]. The microwave-assisted nonaqueous routes are also relevant for the synthesis of non-oxide nanomaterials such as metals and metal chalcogenides [113]. 

Flexible electronic devices are increasingly capturing the attention of researchers in radio frequency (RF) technologies and metamaterials physics, and are not limited to electronics applications such as light emitting diodes (7). These devices are driven by the pliable, conformal, and stretchable characteristics of elastomeric substrates [7-13], Examples of RF and terahertz devices demonstrated on flexible device platforms include curved antennas [12], millimeter-wave patch flexible antennas and coupled line filters [13], coplanar waveguide antenna [14], stretchable microfluidic RF antenna [15], frequency selective surfaces and metamaterials [8], microwave frequency switches [16], tunable metamaterials [17, 18], and tunable dielectric and magnetic properties [10]. 

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