Planar digital nanoliter dispensing system based on thermocapillary actuation

Abstract

We provide guidelines for the design and operation of a planar digital nanodispensing system based on thermocapillary actuation. Thin metallic microheaters embedded within a chemically patterned glass substrate are electronically activated to generate and control 2D surface temperature distributions which either arrest or trigger liquid flow and droplet formation on demand. This flow control is a consequence of the variation of a liquid's surface tension with temperature, which is used to draw liquid toward cooler regions of the supporting substrate. A liquid sample consisting of several microliters is placed on a flat rectangular supply cell defined by chemical patterning. Thermocapillary switches are then activated to extract a slender fluid filament from the cell and to divide the filament into an array of droplets whose position and volume are digitally controlled. Experimental results for the power required to extract a filament and to divide it into two or more droplets as a function of geometric and operating parameters are in excellent agreement with hydrodynamic simulations. The capability to dispense ultralow volumes onto a 2D substrate extends the functionality of microfluidic devices based on thermocapillary actuation previously shown effective in routing and mixing nanoliter liquid samples on glass or silicon substrates.

Reducing Adhesion for Dispensing Tiny Water/Oil Droplets and Gas Bubbles by Femtosecond Laser‐Treated Needle Nozzles: Superhydrophobicity, Superoleophobicity, and Superaerophobicity

“…Generation and manipulation of tiny liquid droplets (down to micro‐ or nanoliter scale) and fine bubbles have attracted an ever increasing amount of interest because of the broad applications, such as liquid transportation, inkjet printing, high‐resolution three‐dimensional (3D) printing, cell engineering, micro‐reactor, bio‐analysis, bio‐sensing, energy production, chemical engineering, and environmental remediation . Signicant efforts have been devoted from scientific and industrial communities to produce smaller droplets by reducing the nozzle size or through assistance of special driving mechanisms (e. g., mechanical‐, electrical‐, and thermal‐driven equipments) in the past . However, the traditional nozzles and dispensing methods still face many limitations.…”

Superamphiphobic Bionic Proboscis for Contamination‐Free Manipulation of Nano and Core–Shell Droplets

“…These water‐in‐oil droplet systems drastically increase throughput rates as each nanoliter droplet functions as a separate reaction vessel. Despite progress, development of compact low‐cost tools capable of contamination‐free nanoliter droplet manipulation remains elusive, and current approaches are based on bulky mechanical‐, thermal, electrical, and pyroelectrodynamics‐driven systems. These latter designs may experience contamination stemming from liquid residue adhering to the surfaces of tips or nozzles .…”

Applications of EWOD Systems for DNA Reaction and Analysis

“…Different methods of droplet actuation have been studied including thermocapillarity force [3][4][5][6], surface acoustic waves (SAWs) [7][8][9], dielectrophoresis [10][11][12][13], optoelectrowetting [14][15][16][17], mechanical actuation [18][19][20] and eletrowetting-ondielectic (EWOD) [1,[21][22][23][24][25][26][27][28][29]. Among these methods, EWOD is well-known and promising technique in a digital droplet-based microfluidic system, an open structure where discrete droplets are manipulated on substrate surface using electrowetting.…”