1. Structural design is a route to stretchability for rigid conductive materials. Examples of such structures include microcracks formed by metal thin films on elastic substrates, liquid metal deposited on such metal films, fractal design, serpentine structure, helical structure, outer plane wave structure, open grid (Open-mesh) structure, paper-cut (Kirigami) structure and three-dimensional porous structure.
2. In-plane serpentine structures are used to realize highly stretchable electronic circuits. The stretchability of the serpentine structure comes from the extension of its sinuous “two-dimensional spring” structure.
3. Out-of-plane wavy structures can be made with highly conductive metals or conductive nanomaterials into thin films or ribbons to make out-of-plane buckles which can achieve superelasticity of ≈1500% without electrical failure.
The article provides an overview of various types of flexible and stretchable sensors and their structures. It is well written and provides detailed information about the different types of structures that can be used to create flexible and stretchable sensors. However, there are some potential biases in the article that should be noted. For example, it does not provide any information about the potential risks associated with using these sensors or any counterarguments to the claims made in the article. Additionally, it does not present both sides equally as it only focuses on the advantages of using these sensors without exploring any potential drawbacks or limitations. Furthermore, some of the claims made in the article are unsupported and lack evidence which could lead readers to question its trustworthiness and reliability. Finally, there is a possibility that some promotional content has been included in order to increase sales for certain products mentioned in the article which could lead readers to doubt its impartiality.