Bioinspired Tip-Guidance Liquid Jetting and Droplet Emission at a Rotary Disk via a Surface Energy Gradient

Abstract

Effective droplet emission is of fundamental importance for practical application, such as agricultural sprays to painting, atomization, emulsification, and catalytic action. Highly viscous liquids are commonly used, such as printing inks, which hinder the ejection at the nozzle. A big challenge faced by people is how to obtain stable and controllable liquid droplets in a wide range of viscosities. Inspired by the rotation shaking of droplets on fiber clusters and the rotary spraying disk technique, here, we demonstrate uniform microdroplet (1–2000 mPa·s) generation in a tip-guided way that replaces the commonly confined nozzle by a double-layer spinning “sandwich” multitip disk (SSMD). A surface energy gradient induced by the margin structure of the alternating gas wedge and solid tip guides liquid to move along the solid tip, which is ejected at the end of the tip, forming a ring of droplet clusters. SSMD improves the effective droplet-jet process to 7/10 of the whole drainage process and enhances the efficiency with a production drop volume of ∼3.19 × 107 μL/h and production droplet numbers of ∼3.3 × 104 per second. Droplets can be fine-tuned between 0.1 and 1.0 mm via the tip structure, liquid property, and spinning angular velocity with a narrow size distribution. This facile tip-guided design could inspire the possibility of energy-efficient droplet production techniques in various fluid applications, such as spraying and printing. It may further improve other fluid systems that serve as a crucial component for high-speed droplet manipulation, liquid transport, and water vapor capturing.

Introduction to the biomimetic design of interfacial materials for water overflow control

“…Wang et al prepared the multi-tip spinning devices via integrating the behavioral bionics and the morphologic bionics of the unique curvature structure of the leaf tip. 35 Confined by the tip structure, the emission of droplets with a wide range of viscosities and radii of 0.1-10 mm was realized (Fig. 6(c)).…”

“…38 with permission from Wiley-VCH, copyright 2017 38 Since 2013, overflow in multiple length scales, from macroscales to micro-scales, has aroused broad concerns. Researches and evolutions of overflow manipulation technology profoundly influence many aspects of our lives, and examples include dispensing with precise volume, 9,35 walking or travelling without unwanted splash, 11 uni-directional transport of liquid over a long-distance and high-speed, [25][26][27][28][29][30][31][32] and effective drainage facility and agricultural applications. [38][39][40][41][42][43][44][45][46] As a perspective, we wish the overflow control technology will become a reality to collect fog or mist from air for irrigation and for precise deposition [40][41][42][43][44][45][46] of sprays 35 for agricultural production (Fig.…”

“…Conventional agricultural spray involves a wide range of medicines such as powder and emulsifiable concentrate as pesticides or nutrients, 35 which can improve the viscosity of liquids. A critical problem is the efficient and stable atomization of high-viscosity liquids, which favors clogging the nozzle and hindering the ejection.…”

Dynamics of Drop Release from the Edge of a Spinning Disc

“…Peng et al have studied regime changes with flow rate and rotational speed using high-speed imaging. The improved control on drop release in ligament mode has led to studies on discs of different designs. − Guided drop formation in ligament mode is recently achieved by Wang et al using a stacked serrated disc. The authors suggest that pointed tips in their disc increase the frequency of drop formation by promoting jet formation for low-to-moderate viscosity liquids.…”

Announcing the 2020 ACS Nano Award Lecture Laureates

“…Lei Jiang is a member of the Chinese Academy of Sciences (CAS) and on the faculty of the CAS Technical Institute of Physics and Chemistry, as well as the dean of the School of Chemistry of Beihang University. He is a world leader in understanding and synthetic recapitulation of the interesting and useful properties of natural materials with nanoscale structures. − He serves on our editorial advisory board and is a frequent advisor and author. He is exceptionally creative and is known for his insightful and entertaining lectures.…”