Responsive polymer materials can adapt to surrounding environments, regulate transport of ions and molecules, change wettability and adhesion of different species on external stimuli, or convert chemical and biochemical signals into optical, electrical, thermal and mechanical signals, and vice versa. These materials are playing an increasingly important part in a diverse range of applications, such as drug delivery, diagnostics, tissue engineering and 'smart' optical systems, as well as biosensors, microelectromechanical systems, coatings and textiles. We review recent advances and challenges in the developments towards applications of stimuli-responsive polymeric materials that are self-assembled from nanostructured building blocks. We also provide a critical outline of emerging developments.

The English-language dictionary defines wrinkles as ''small furrows, ridges, or creases on a normally smooth surface, caused by crumpling, folding, or shrinking''. In this paper we review the scientific aspects of wrinkling and the related phenomenon of buckling. Specifically, we discuss how and why wrinkles/buckles form in various materials. We also describe several examples from everyday life, which demonstrate that wrinkling or buckling is indeed a commonplace phenomenon that spans a multitude of length scales. We will emphasize that wrinkling is not always a frustrating feature (e.g., wrinkles in human skin), as it can help to assemble new structures, understand important physical phenomena, and even assist in characterizing chief material properties.

. Here we show that model elastomeric artifi cial skins wrinkle in a hierarchical pattern consisting of self-similar buckles extending over fi ve orders of magnitude in length scale, ranging from a few nanometres to a few millimetres. We provide a mechanism for the formation of this hierarchical wrinkling pattern, and quantify our experimental fi ndings with both computations and a simple scaling theory. Th is allows us to harness the substrates for applications. In particular, we show how to use the multigeneration-wrinkled substrate for separating particles based on their size, while simultaneously forming linear chains of monodisperse particles.Wrinkling, buckling and other mechanical instabilities have been typically treated as a nuisance to be avoided rather than an exquisite pattern to be exploited. Although this view is changing with the growing understanding of how ubiquitous these phenomena are 9 , the utilization of wrinkling in applications has been hampered by the absence of a detailed understanding of the phenomena, as well as the ability to control it experimentally. Here we focus on the tunable hierarchical wrinkling of model stiff elastomeric artifi cial skins supported on a soft base. These wrinkles are fabricated by uniaxially stretching poly(dimethyl siloxane) (PDMS) network sheets (thickness ∼0.5 mm, Young modulus ∼1 MPa) 10 in a custom-designed stretching apparatus 11 and exposing them to ultraviolet/ozone (UVO) radiation for extended periods of time (30-60 minutes). Previous studies established that the UVO treatment of PDMS converts the fi rst ∼5 nm of the PDMS surface into a stiff 'skin' 12 , whose density is approximately a half of that of silica 13 . Optical microscopy and scanning force microscopy (SFM) experiments confi rm that the surfaces are originally fl at in the presence of strain.After the UVO treatment, the strain is removed from the specimen and, the skin buckles perpendicularly to the direction of the strain. The buckle morphology depends on the strain removal rate. Specifically, stretched and UVO-modified specimens released at a fast rate (strain removed abruptly)

In this review, a brief synopsis of superhydrophobicity (i.e. extreme non-wettability) and its implications on marine fouling are presented. A short overview of wettability and recent experimental developments aimed at fabricating superhydrophobic surfaces by tailoring their chemical nature and physical appearance (i.e. substratum texture) are reviewed. The formation of responsive/"smart" surfaces, which adjust their physico-chemical properties to variations in some outside physical stimulus, including light, temperature, electric field, or solvent, is also described. Finally, implications of tailoring the surface chemistry, texture, and responsiveness of surfaces on the design of effective marine fouling coatings are considered and discussed.

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