Water-responsive pressure-sensitive adhesive with reversibly changeable adhesion for fabrication of stretchable devices

Owing to the extremely low stiffness of elastomeric materials commonly used as substrates of stretchable devices, fabrication of stretchable devices is usually performed with an elastic film attached to a rigid temporary substrate. The problem is that the stress applied to the elastic film during peeling induces a severely large deformation of the film, resulting in performance degradation of the devices formed thereon. To address this, a water-induced, softly peelable, pressure-sensitive adhesive (wisp-PSA) was developed by synthesizing a new amphiphilic oligomer and mixing it with acryl-based PSA. As amphiphilic oligomers facilitate more water uptake in the adhesive layer, hydrogen bonding between the polymers and water molecules weakens the hydrogen bonding in the polymers and to the substrate, resulting in decrease in adhesion. The initial adhesion strength of the wisp-PSA, which reached about 152 N/m, was dramatically dropped to about 8 N/m after immersing in water. Through the use of wisp-PSA, polyurethane film with Ag nanowires formed thereon could be safely peeled, without damage, from the glass after immersion in warm water. Furthermore, the adhesion strength lowered by the water treatment was almost restored when the water absorbed by the oligomer was dried, revealing that the developed wisp-PSA is reusable.