Investigation of Laplace Barriers for Arrayed Electrowetting Lab-on-a-Chip

Abstract

Partial-post Laplace barriers have been postulated as a means to allow electrowetting transport and geometrical reshaping of fluids, followed by the preservation of fluid geometry after the electrowetting voltage is removed. Reported here is the first investigation of Laplace barriers with the arrayed electrodes and splitting/merging transport functions for an electrowetting lab-on-a-chip. Laplace barriers optimized for 500 × 500 μm(2) electrodes and 78 μm channel height are shown to provide geometrical control of fluid shape down to radii of curvature of ~70 μm. The Laplace barriers increase the splitting volume error, but with proper electrical control, the average error in the split volume is reduced to 5%. Improved programmable fluid storage in droplets or reservoirs and continuous channel flow are also shown. This work confirms the potential benefits of Laplace barriers for lab-on-a-chip and also reveals the unique challenges and operation requirements for Laplace barriers in lab-on-a-chip applications.

Oil Motion Control by an Extra Pinning Structure in Electro-Fluidic Display

“…Electrowetting has shown its power in manipulating micro-fluidics, which inspired applications like microfluidic chips [ 1 , 2 ] as well as electro-fluidic displays (EFD) [ 3 ]. To EFD, an oil/water two-phase microfluidic system, the oil motion control is the key for its optical performance, like gray scale, switching response, maximum aperture ratio, oil contraction direction, and so on [ 4 , 5 ].Therefore, the dynamic of oil/water interfacial movement attracts great attention in this field [ 6 , 7 , 8 , 9 , 10 , 11 ]. For a typical EFD pixel ( Figure 1 ), which is sub-millimeterin size, the dominant driving forces for oil motion are recognized as interfacial tension and electrostatic force [ 12 ].…”

“…The artificially designed difference in the electric field distribution shows reasonable guidance in the final location of oil contraction for pixel switching-on [ 4 ]. However, the in-smooth electrode edge brought by “notch” may generate localized high Maxwell stress, which increasesthe risk of dielectric breakdown and oil motion disturbance [ 7 , 11 , 14 , 15 ]. On the other hand, the driving schemes with different rising gradients also show significant influence on oil motion patterns inside pixels.…”

Effect of an external electric field on capillary filling of water in hydrophilic silica nanochannels

“…2,[20][21][22][23] In addition, water molecules are highly polar and hence, molecular ordering of water within ultraconfined structures can be altered by exposure to electromagnetic fields. [23][24][25] In this context, a variety of techniques like direct modification of the surface charge density, 26,27 , tuning the solid-liquid interfacial tension by applying electric potentials 28 , field effects induced by surface embedded electrodes 29,30 and electric, 24,31,32 and magnetic far field effects 33 have been used for manipulation of aqueous solutions in nanoconfinement. Furthermore, recent studies have revealed the significant effect of varying external applied electric fields on flow control by tuning the electrical double layer thickness, 29,34 the electro-osmotic flow velocity [35][36][37] and the pressurized water flow rates.…”

Bio-Inspired Polymeric Structures with Special Wettability and Their Applications: An Overview

“…For technical applications, wettability is an essential property in painting [7,8], printing [9,10,11], anti-fogging [12,13,14], anti-fouling [15,16,17,18], transportation [19,20,21,22], waterproof products [23,24,25], oil recovery [26,27,28], anti-corrosion [29,30,31], water recycling, etc. [4,32,33,34,35,36,37,38,39] On the micro-/nanoscale, wettability affects micromachining, such as microfluidic channels [40,41,42], nanoprinting [43,44], and lab-on-a-chip systems [45,46].…”