Electrostatic interactions determine the key properties of several materials that promise to enable revolutionary nanotechnologies. For example, the power delivered by ionic liquid-based supercapacitors, and the curing time of bio-inspired surgical adhesives, both hinge on the collective behavior of large ensembles of ions in confined interfaces. However, a comprehensive framework for understanding and influencing electrostatic interactions in highly concentrated electrolytes remains elusive. We address this knowledge gap by using nanoscale force-distance measurements to investigate and tune electrostatic interactions in interfaces containing high ionic densities, with an aim of providing quantitative molecular foundations to guide nanomaterials design.

In this dissertation, we first review our extension of the Surface Forces Apparatus technique (SFA) to enable force-distance measurements with in situ electrochemical control (the EC SFA). Next, we discuss how EC SFA experiments were combined with temperature-controlled SFA measurements to demonstrate that the electrostatic screening properties of ionic liquids can be rationalized using mean-field theories by focusing on local excess charge densities, as opposed to explicitly accounting for the distribution of every ion. Finally, we illustrate the pivotal role of electrostatic interactions in governing the adhesive performance of mussel-mimetic peptides and conclude with an analysis of how natural proteins provide molecular themes that may guide the design of biomedical adhesives.