Smart Anisotropic Wetting Surfaces with Reversed pH‐Responsive Wetting Directions

Abstract

Smart pH‐responsive surfaces that could autonomously induce unidirectional wetting of acid and base with reversed directions are fabricated. The smart surfaces, consisting of chemistry‐asymmetric “Janus” silicon cylinder arrays (Si‐CAs), are prepared by precise modification of functional groups on each cylinder unit. Herein, amino and carboxyl groups are chosen as typical pH‐responsive groups, owing to their protonation/deprotonation effect in response to pH of the contacted aqueous solution. One side of the Si‐CAs is modified by poly(2‐(dimethylamino)ethyl methacrylate), while the other side is modified by mixed self‐assembled monolayers of 1‐dodecanethiol and 11‐mercaptoundecanoic acid. On such surfaces, it is observed that acid and base wet in a unidirectional manner toward corresponding directions that are modified by amino or carboxyl groups, which is caused by asynchronous change of wetting property on two sides of the asymmetric structures. The as‐prepared Janus surfaces could regulate the wetting behavior of acid and base and could direct unidirectional wetting of water with reversed directions when the surfaces are treated by strong acid or base. Due to the excellent response capability, the smart surfaces are potential candidates to be applied in sensors, microfluidics, oil/water separation, and smart interfacial design.

Biaxially Morphing Droplet Shape by an Active Surface

“…[ 18–21 ] Recent advances have brought diverse approaches to create specific wetting performance by using chemical treatment, [ 22–24 ] dedicated pattern designs, [ 25–27 ] and functional materials. [ 28,29 ] Notably, Quéré and co‐workers [ 16 ] manipulated the droplet shape on an elastic surface with soft pillars. Park and Kim used a shape memory polymer‐based structure to shape droplets with adjustable surface morphology.…”

Design of Active Interfaces Using Responsive Molecular Components

“…Patterning has proved to be useful to introduce a new dimension of functionality at interfaces. For example, Ge et al reported pH‐responsive surfaces that could differentiate between basic and acidic aqueous solutions and show an inverse anisotropic wetting behavior ( Figure a–f) . Key elements are Janus silicon cylinder arrays (Si‐CAs).…”

“…f) Photographs of droplets at pH values between 0.98 and 13.05. Adapted with permission . Copyright 2018, Wiley‐VCH.…”

Cellulose Fibrils Extracted from Bamboo Chips as a Reinforcing Material for Prolonged Drug Release

“…[20] Furthermore, 2-(Dimethylamino) ethyl methacrylate (DMAEMA), which is a kind of intelligent polymer with both temperature and pH sensitivity, has been a potential polycationic carrier and can adjust the phase transition at 14 ∼ 50°C with the protonation degree of the side chain tertiary amine group, both in vitro and in vivo. [21] Combining PEI and PDMAEMA could improve transgene expression efficiency without decreasing cell viability for in vivo systems, and make it a potential combination of applications in biomaterials. [22,23] These reports suggested that, for stimuliresponsive system, the effective combination of cellulose, PEI and PDMAEMA would benefit from an integrative strategy, but is this technically possible?…”