In nature, interfacial molecular interactions are at the heart of all biological processes and are mediated by diverse stimuli. Inspired by nature's responsive mechanisms and our increased capability to manipulate matter at the molecular level, new bio-interface materials are being developed that respond efficiently to a variety of external stimuli. In this Review, we discuss emerging methods for imparting surfaces with dynamic properties and how this, in turn, is leading to increased functional complexity at the bio-interface. We examine how recent advances are becoming important in providing new insights into cell behaviour and spurring substantial progress in the fields of regenerative medicine and tissue engineering. These advances provide new opportunities to address the complex issues associated with biofouling and facilitate the production of implantable on-demand sensing devices and highly effective delivery, bioseparation and bioelectrocatalytic systems. Although progress is being made, we also highlight that current methods are still limited in their capability to impart complex functionality onto the bio-interface to fully address the current challenges in biotechnology and biomedicine. Exciting prospects include the incorporation of full reversibility of interactions, a broad repertoire of multi-responsiveness and bidirectional actuation at the bio-interface, as well as the capability to incorporate the developed systems in practical applications.