Interfacial Stress in Physically Transient Layered Structures: An Experimental and Analytical Approach

Transient materials are an emerging class of materials that are designed to undergo disintegration at a predefined rate and a predefined manner. Transient materials are utilized in structures and devices to enable device transiency, in particular, transient electronics. While interfacial stress in layered structures is well studied and-to a large extent-well understood, the same in transient layered structures remains a challenging matter to study and understand. This is solely because of the dynamic chemical and physical properties of the transient materials as well as swelling-induced stress that is introduced to the interface due to the mismatch in physical properties of the dissimilar materials forming layers. In this work, interfacial interactions of a particular case of polymeric substrate with lithium titanate electrode coating layer are studied and reported. The structure is analogous to that of the anode in a type of lithium-ion batteries; yet, it can be extended to more general cases of soft electronics. This coordinated experimental-analytical simulation study exhibits formation, accumulation, and propagation of swelling-induced stress through the membrane-coating interface, when in transient mode. Swelling-induced stress as a function of electrode thickness is studied; the analytical data and simulations are verified by experimental results. The stress analysis method can be extended to analyze interfacial stress in a wide range of layered structures with dynamic properties.