Programmable intelligent liquid matter: material, science and technology

Abstract

Intelligent responses, transformation and desired delivery of liquids involve the intersection among materials, physics, and chemistry. The precise programmed operation has been found rather significant in many emerging fields, such as microfluidic devices, digital fluids, intelligent matter, responsive liquid machines, interactive display, soft robotic system and drug delivery, etc. This article is dedicated to presenting a comprehensive review of recent advances in the programmable actuation of liquid matter controlled by unique substrate structures and various physical fields. First, the fundamental theories of asymmetric surface microstructure and specifically administrated external effects such as electric, magnetic, acoustic, light, and thermal fields to drive droplets are illustrated. Then, we compare the advantages and disadvantages of these typical technological strategies. Furthermore, the practical multifunctional extension of programmable liquids based on different actuation mechanisms is presented. Finally, we summarize the design schemes of programming units for liquid matter and give perspective on possible future research directions, providing a brief reference for researchers interested in the field.

Designing of anisotropic gradient surfaces for directional liquid transport: Fundamentals, construction, and applications

“… 1 The material systems that allow the spontaneous flow/penetration of liquid in only one direction are described as liquid diodes, which attract scientific and application interests in diverse fields such as liquid separation, water collection, digital microfluids 2 (enable fluidic functions at microscale for merging, splitting, transporting, mixing, and incubating, which makes them ideal for numerous biological and chemical platforms), energy, interface catalysis, and smart fabrics. 3 , 4 , 5 , 6 , 7 , 8 The anisotropic motion of droplets on a solid substrate was first observed by Greenspan in 1978. 9 The author pointed out that droplets tend to creep in a direction of greater adherence (lower contact angle) while retracting from weaker attachment regions (higher contact angle) because of the forces at the fluid/solid contact line.…”

Remote actuation based on magnetically responsive pillar arrays

“…As for the actuation strategies, the use of a magnetic field has been one of the most common methods due to its instantaneous response, nondestructive and untethered control [20,36,37]. Recently, some research reported positional manipulation of small objects by employing a magnetic field, liquid mixed with magnetic particles was used [38]. These methods mean that the transported objects must be magnetic or be attached with magnetism.…”