Bioinspired Materials for Self-Cleaning and Self-Healing

Abstract

Biological systems have the ability to sense, react, regulate, grow, regenerate, and heal. Recent advances in materials chemistry and micro-and nanoscale fabrication techniques have enabled biologically inspired materials systems that mimic many of these remarkable functions. This issue of MRS Bulletin highlights two promising classes of bioinspired materials systems: surfaces that can self-clean and polymers that can self-heal. Self-cleaning surfaces are based on the superhydrophobic effect, which causes water droplets to roll off with ease, carrying away dirt and debris. Design of these surfaces is inspired by the hydrophobic micro-and nanostructures of a lotus leaf. Self-healing materials are motivated by biological systems in which damage triggers a site-specific, autonomic healing response. Self-healing has been achieved using several different approaches for storing and triggering healing functionality in the polymer. In this issue, we examine the most successful strategies for self-cleaning and self-healing materials and discuss future research directions and opportunities for commercial applications. Bioinspired Materialsfor Self-Cleaning and Self-Healing Jeffrey P. Youngblood and Nancy R. Sottos, Guest Editors water droplets. 11-13 Self-healing materials are inspired by living systems in which minor damage (e.g., a contusion or bruise) triggers an autonomic healing response. Successful healing relies on seamless integration of reactive chemical functionality into a polymer or polymer composite at the microscale, nanoscale, or molecular level. Although these two functions are quite different, together they represent the wide range of autonomic responses achievable through bioinspired design. In this article, we separately introduce the key elements of self-cleaning and self-healing materials systems and identify the scientific challenges and successful strategies for continued advancement of these nascent fields. Self-Cleaning SurfacesInterest in self-cleaning surfaces has been rekindled because of the newfound ability to structure surfaces on the submicron scale over large planar areas relevant to macroscale wetting. These structured surfaces allow the so-called "lotus-leaf effect," whereby water droplets are shed easily from certain structures, carrying away dirt and other debris. 11-13 Such bioinspired topographical methods toward self-cleaning are the focus of this review.

Biomimetics: lessons from nature–an overview

“…Fibroblast cells migrate to the wound site, enabling the creation of granulation tissue to fill the wound (Singer & Clark 1999). (b) Demonstration of bioinspired damage-triggered release of a microencapsulated healing agent in a polymer specimen: (i) schematic of compartmentalized healing agent stored in a matrix, (ii) release of dyed healing agent into the crack plane, which leads to a synthetic slotting (polymerization) process to bond the crack faces, and (iii) one-half of the fracture surface revealing ruptured capsules ( Youngblood & Sottos 2008). damaged living tissues can heal themselves by the formation of an intermediate tissue (based on the response to inflammation) followed by the scar tissue (Fratzl & Weinkamer 2007).…”

The design and applications of superomniphobic surfaces

“…These issues are similar to the challenges faced by hierarchically structured superhydrophobic surfaces. The industrial perspective on the challenges associated with durability of superhydrophobic surfaces is perhaps best provided by Extrand, as noted in his previous work 88 : 'during one of our technology update forums, we showed water bouncing off a super-hydrophobic surfaceyThe initial response was a combination of amazement and excitement. Enthusiasm quickly waned when one of our executives innocently touched the surface with his finger, destroying its superhydrophobic nature.'…”

Assessing durability of superhydrophobic surfaces

“…As such, the success of a SHS depends not only on its wetting performances but also on its ability to last over time and resist to erosion and abrasion. 14,15 Nonetheless, only few papers so far have addressed the durability issues, each of them using a different method to assess surface durability, [16][17][18] so that a Assessing durability of superhydrophobic surfaces Malavasi, Bernagozzi, Antonini and Marengo systematic approach to the issue of durability is still lacking in the literature.…”