Pumpless dispensing of a droplet by breaking up a liquid bridge formed by electric induction

Abstract

Dispensing uniform pico-to-nanoliter droplets has become one of essential components in various application fields from high-throughput bio-analysis to printing. In this study, a new method is suggested and demonstrated for dispensing a droplet on the top plate with an inverted geometry by using electric field. The process of dispensing droplets consists of two stages: (i) formation of liquid bridge by moving up the charged fluid mass using the electrostatic force between the charges on the fluid mass and the induced charges on the substrate and (ii) its break-up by the motion of the top plate. Different from conventional electrohydrodynamic methods, electric induction enables the droplets to be dispensed on various surfaces including non-conducting substrate. The use of capillarity with an inverted geometry removes the need of external pumps or elaborates control for constant flow feed. The droplet diameter has been characterized as a function of the nozzle-to-plate distance and the plate moving velocity. The robustness of the present method is shown in terms of nozzle length and applied voltage. Finally, its practical applicability is confirmed by rendering a 19 by 24 array of highly uniform droplets with only 1.8% size variation without use of any active feedback control.

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

“…The inner wall functionalization prevent in‐needle adhesion, enabling superior control over droplet release and size, while resisting contamination by capillary rise (Figure b,c). The need to break capillary‐bridges for droplet detachment is also prevented, further reducing the risk of contaminating the inner walls with liquid residues. The outer surface functionalization prevents contamination by creep during droplet generation and immersion in liquids (Figure d,e).…”

“…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 .…”

“…These latter designs may experience contamination stemming from liquid residue adhering to the surfaces of tips or nozzles . Despite numerous advantages, these techniques have strict requirements such as high voltages, heat injection, and laser drilling, which increase complexity of manufacturing and limits end‐user compatibility and, in some instances, scalability.…”

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.…”

“…[1][2][3][4][5][6] 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. [7][8][9][10] However, the traditional nozzles and dispensing methods still face many limitations. For instance, the driving equipment usually makes the dispensing system become bulky and also increase the complexity of operation.…”