Fig. 3: Overcoming the adhesion paradox through controlling surface roughness at the macro-scale.
From: Shape memory polymer surfaces with controllable roughness for multiscale switchable dry adhesion
a Schematic illustrations of the modulation of surface roughness on the nanotipped SMP surface, along with SEM images contrasting the original nanotipped SMP surface and its flattened surface, exhibiting reduced surface roughness. b 3D optical profiles of the nanotipped SMP surface and its flattened surface captured using a 3D confocal scanning microscope (Optelics hybrid C3, Lasertec, Japan) and (c) their roughness power spectra. d Optical microscopy image of a fabric and the nanotipped SMP surface adhering to the fabric (The character image is provided by POSTECH). e Switchable adhesion of the nanotipped SMP surface on the fabric (The character image is provided by POSTECH). f The nanotipped SMP surface adhering to a wet fabric. (i) Heat the nanotipped SMP surface above its Tg. (ii) Wet the fabric. (iii) Press the heated nanotipped SMP surface onto the wet fabric and cool it down. (iv) The nanotipped SMP surface adheres well even to the wet fabric (The character image is provided by POSTECH). g Adhesion switchability of the nanotipped SMP surface on various types of surfaces (Adhesion tests were conducted five times for each type of surface). Data are presented as mean values with error bars indicating the minimum and maximum values. h Easy self-release of the nanotipped SMP surface due to its extreme adhesion switchability. (i) Both the nanotipped SMP surface and the flat SMP surface strongly adhere to the glass beaker. (ii) Hot water is poured into the beaker. (iii) Only the nanotipped SMP surface can self-release.
