Roll-to-roll fabrication of touch-responsive cellulose photonic laminates

TLDR

Hydroxypropyl‑cellulose self‑assembles into helical nanostructures that produce vivid Bragg‑reflection colours, and its periodicity is highly pressure‑sensitive, yet scalable, real‑world applications remain limited. This study aims to roll‑to‑roll fabricate metre‑scale HPC laminates for pressure‑responsive photonic use. The laminates are produced by continuous coating and encapsulation, and their pressure response is quantified by measuring optical hue change and digital imaging. We demonstrate real‑time pressure mapping of a human foot‑print on the laminates, marking the first large‑area, cost‑effective method to generate pressure‑responsive photonic films readable with standard cameras.

Abstract

Abstract Hydroxypropyl-cellulose (HPC), a derivative of naturally abundant cellulose, can self-assemble into helical nanostructures that lead to striking colouration from Bragg reflections. The helical periodicity is very sensitive to pressure, rendering HPC a responsive photonic material. Recent advances in elucidating these HPC mechano-chromic properties have so-far delivered few real-world applications, which require both up-scaling fabrication and digital translation of their colour changes. Here we present roll-to-roll manufactured metre-scale HPC laminates using continuous coating and encapsulation. We quantify the pressure response of the encapsulated HPC using optical analyses of the pressure-induced hue change as perceived by the human eye and digital imaging. Finally, we show the ability to capture real-time pressure distributions and temporal evolution of a human foot-print on our HPC laminates. This is the first demonstration of a large area and cost-effective method for fabricating HPC stimuli-responsive photonic films, which can generate pressure maps that can be read out with standard cameras.