Charles H. Barty-King

1 Introduction Hydroxypropyl cellulose (HPC) is well established in the medical, pharmaceutical, and food industries as a widely applicable non-toxic, and cost-effective raw material.[1-15] More recently however, HPC has gained interest as an applied photonic material specifically,[16-21] due to its remarkable mechanochromic properties (i.e., changes of color with strain).[22-25] Shown to have great potential for optical strain sensing applications,[16-18, 26-28] mechanochromic HPC can be...

Abstract Hydroxypropyl cellulose (HPC) is an edible, cost-effective and widely used derivative of cellulose. Under lyotropic conditions in water, HPC forms a photonic, liquid crystalline mesophase with an exceptional mechanochromic response. However, due to insufficient physical cross-linking photonic HPC can flow freely as a viscous liquid, preventing the exploitation of this mechanochromic material in the absence of any external encapsulation or structural confinement.

The HPC lamination process starts with R2R coating of an HPC solution, followed by an edge sealing coating and curing, and a continuous film-to-film lamination to encapsulate the HPC film (Fig. 1a–e). All our coatings are performed on a customised Smartcoater 28 (Coatema Coating Machinery GmbH) R2R tool on 75 µm thick polyethylene terephthalate (PET) films.