Insights into Nanoscale Adhesion via In Situ Transmission Electron Microscopy

Adhesion governs the performance of material interfaces, from large-scale applications such as the energy loss in an automobile engine to small-scale applications such as the stability of nanoparticles. An emerging technique for investigating nanoscale adhesion is performing nanoscale contact-and-separation tests via <i>in situ </i>transmission electron microscopy. In this work, we used this technique to reveal fundamental principles of nanoscale adhesion. First, we showed that nanoscale adhesion is governed primarily by strength-limited separation, rather than by fracture as previously believed. Here our adhesion tests of nanoscale contacts demonstrated the need for a different paradigm in interpreting nanoscale adhesion data. Next, we measured the nanoscale adhesion of noble-metal nanoparticles to their oxide supports, a critical parameter related to the efficiency and lifetime of nanoparticle technologies. In addition to validating our measurements with reported trends in adhesion energy, the flexibility of our technique enabled the characterization of new combinations of nanoparticles and supports. Finally, we demonstrated that the adhesive strength between a nanoparticle and its support is highly sensitive to the properties of the nanoparticles such as composition and size. Together, these results enable new fundamental insight into nanoscale adhesion that will inform the design of emerging technologies.