Predicting the Electrical, Mechanical, and Geometric Contributions to Soft Electroadhesives through Fracture Mechanics.

Electroadhesion is the modulation of adhesive forces through electrostatic interactions and has potential applications in a number of next-generation technologies. Recent efforts have focused on using electroadhesion in soft robotics, haptics, and biointerfaces that often involve compliant materials and nonplanar geometries. Current models for electroadhesion provide limited insight on other contributions that are known to influence adhesion performance, such as geometry and material properties.

Geometry-controlled instabilities for soft-soft adhesive interfaces.

Soft materials interfaces can develop complex morphologies, such as cavities or finger-like features, during separation as a result of a mechanical instability. While the onset and growth of these instabilities have been investigated previously for interfaces between rigid and soft materials, no existing predictive model provides insight for controlling the separation morphology associated with these instabilities when both "sides" of the interface are soft. Here, we expand previous models to account for the geometry and materials properties of two soft materials that form an interface.

Branched Side Chains Govern Counterion Position and Doping Mechanism in Conjugated Polythiophenes.

Predicting the interactions between a semiconducting polymer and dopant is not straightforward due to the intrinsic structural and energetic disorder in polymeric systems. Although the driving force for efficient charge transfer depends on a favorable offset between the electron donor and acceptor, we demonstrate that the efficacy of doping also relies on structural constraints of incorporating a dopant molecule into the semiconducting polymer film. Here, we report the evolution in spectroscopic and electrical properties of a model conjugated polymer upon exposure to two dopant types: one that directly oxidizes the polymeric backbone and one that protonates the polymer backbone.

Morphology controls the thermoelectric power factor of a doped semiconducting polymer.

The electrical performance of doped semiconducting polymers is strongly governed by processing methods and underlying thin-film microstructure. We report on the influence of different doping methods (solution versus vapor) on the thermoelectric power factor (PF) of PBTTT molecularly p-doped with F TCNQ ( = 2 or 4). The vapor-doped films have more than two orders of magnitude higher electronic conductivity (σ) relative to solution-doped films.

Sub-particle reaction and photocurrent mapping to optimize catalyst-modified photoanodes.

The splitting of water photoelectrochemically into hydrogen and oxygen represents a promising technology for converting solar energy to fuel. The main challenge is to ensure that photogenerated holes efficiently oxidize water, which generally requires modification of the photoanode with an oxygen evolution catalyst (OEC) to increase the photocurrent and reduce the onset potential. However, because excess OEC material can hinder light absorption and decrease photoanode performance, its deposition needs to be carefully controlled--yet it is unclear which semiconductor surface sites give optimal improvement if targeted for OEC deposition, and whether sites catalysing water oxidation also contribute to competing charge-carrier recombination with photogenerated electrons.