Low voltage picoliter droplet manipulation utilizing electrowetting-on-dielectric platforms

Abstract

Picoliter droplets actuated on an electrowetting-on-dielectric (EWD) actuator are demonstrated. In this study, the physical scaling of electrodes for 33 μm and 21 μm EWD devices resulted in droplets of 12 pl and 5 pl being dispensed respectively in conjunction with 3 μm SU8 gaskets. The stacked multi-layer insulators in the actuators consisted of 200 nm tantalum pentoxide (Ta2O5) and 200 nm parylene C films deposited and coated with 70 nm of CYTOP. The voltages for dispensing droplets on chips without any external pressure sources are 17.1 Vrms and 22 Vrms for these two sets of devices. A 12 pl droplet can be split into two 6 pl daughter droplets at 18.7 Vrms with 33 μm electrode devices. Droplet manipulation is also demonstrated with paramagnetic beads and buffer solutions with proteins. In addition, electrodes with interlocking protrusions and special featured reservoir gasket are designed to facilitate droplet dispensing on these scaled EWD devices. In order to improve sealing of the two-piece sandwich EWD structure, a soft material, Norland Optical Adhesive (NOA), was coated on the top plate along with pressure on top. We demonstrate that based on fundamental theories and experiments, the dimensional scaling of EWD devices has not yet met a limitation as long as the EWD device can be sealed well.

Constructing 3D heterogeneous hydrogels from electrically manipulated prepolymer droplets and crosslinked microgels

“…1K, are possible. The electromicrofluidic platform is capable of manipulating droplets with large viscosity [1000 cSt ( 21 )] and small volume [5 pl ( 23 )].…”

Creating monodispersed droplets with electrowetting-on-dielectric step emulsification

“…Therefore, it is reasonable to use the contact angle as a tool to adjust the droplet size and offset the effect of fluctuations in the flow rate in step emulsification. The electrowetting-on-dielectric technique 11,12 is well established in digital (i.e. dropletbased) microfluidics to effectively regulate the contact angle.…”

Improving the dielectric properties of an electrowetting-on-dielectric microfluidic device with a low-pressure chemical vapor deposited Si3N4 dielectric layer

“…26 Lin et al used 17 V rms for manipulation of a water droplet. 27 Lee and Kong used a multi-layered dielectric layer composed of amorphous fluoropolymer (AF1600), Si 3 N 4 , and titania (TiO 2 ) to enhance the dielectric quality. 15 deposited on the SiO 2 , Si 3 N 4 , and parylene C films as the composite dielectrics.…”