Abstract

An electrolyte is a substance containing mobile ions. Electrolytes are within us and surround us at every scale: they mediate molecular processes in all living systems, they fill the phone batteries in our pockets, they are the oceans, even interstellar plasmas. Despite the enormous ubiquity and importance of electrolytes, and after two centuries of study, these most ‘ordinary’ of materials continue to challenge us with fascinating puzzles. All electrolytes must obey the same fundamental laws of electrostatics and statistical mechanics, yet the lengthscales and energy of a system can combine in different ways and the result is a multitude of colourful and puzzling phenomena.

In my laboratory we perform high-resolution measurements of the optical and mechanical properties of thin liquid films using a Surface Force Balance (SFB). In this seminar I will present some examples of recent experiments with highly concentrated electrolytes and ionic liquids. I will describe several curious observations, including oscillating charge density in electrical double layers, and anomalously long electrostatic screening lengths observed at high salt concentration.