In situ tunable droplet adhesion on a super-repellent surface via electrostatic induction effect

A comprehensive understanding on droplets

Droplets are ubiquitous and necessary in natural phenomena, daily life, and industrial processes, which play a crucial role in many fields. So, the manipulation of droplets has been extensively investigated for meeting widespread applications, consequently, a great deal of progresses have been achieved across multiple disciplines ranging from chemistry to physics, material, biological, and energy science. For example, microdroplets have been utilized as reactors, colorimetric or electrochemical sensors, drug-delivery carriers, and energy harvesters. Moreover, droplet manipulation is the basis in both fundamental researches and practical applications, especially the combination of smart materials and external fields for achieving multifunctional applications of droplets. In view of this background, this review initiates discussion of the manipulation strategies of droplets including Laplace pressure, wettability gradients, electric field, magnetic force, light and temperature. Thereafter, based on their manipulation strategies, this review mainly summarizes the applications of droplets in the fields of robot, green energy, sensors, biomedical treatments, microreactors and chemical reactions. Application related basic concepts, theories, principles and progresses also have been introduced. Finally, this review addresses the challenges of manipulation and applications of droplets and provides the potential directions for their future development. By presenting these results, we aim to provide a comprehensive overview of water droplets and establish a unified framework that guides the development of droplets in various fields.

Microfluidics-Enabled Soft Manufacture of Materials with Tailorable Wettability

Microfluidics and wettability are interrelated and mutually reinforcing fields, experiencing synergistic growth. Surface wettability is paramount in regulating microfluidic flows for processing and manipulating fluids at the microscale. Microfluidics, in turn, has emerged as a versatile platform for tailoring the wettability of materials. We present a critical review on the microfluidics-enabled soft manufacture (MESM) of materials with well-controlled wettability and their multidisciplinary applications. Microfluidics provides a variety of liquid templates for engineering materials with exquisite composition and morphology, laying the foundation for precisely controlling the wettability. Depending on the degree of ordering, liquid templates are divided into individual droplets, one-dimensional (1D) arrays, and two-dimensional (2D) or three-dimensional (3D) assemblies for the modular fabrication of microparticles, microfibers, and monolithic porous materials, respectively. Future exploration of MESM will enrich the diversity of chemical composition and physical structure for wettability control and thus markedly broaden the application horizons across engineering, physics, chemistry, biology, and medicine. This review aims to systematize this emerging yet robust technology, with the hope of aiding the realization of its full potential.