Active optics with silk

Giulia Guidetti,Fiorenzo G Omenetto,Yu Wang

doi:10.1515/nanoph-2020-0358

Abstract

AbstractOptical devices have been traditionally fabricated using materials whose chemical and physical properties are finely tuned to perform a specific, single, and often static function, whereby devices’ variability is achieved by design changes. Due to the integration of optical systems in multifunctional platforms, there is an increasing need for intrinsic dynamic behavior, such as devices built with materials whose optical response can be programmed to change by leveraging the material’s variability. Here, regenerated silk fibroin is presented as an enabler of devices with active optical response due to the protein’s intrinsic properties. Silk’s abilities to controllably change conformation, reversibly swell and shrink, and degrade in a programmable way affect the form and the response of the optical structure in which it is molded. Representative silk-based devices whose behavior depends on the silk variability are presented and discussed with a particular focus on structures that display reconfigurable, reversibly tunable and physically transient optical responses. Finally, new research directions are envisioned for silk-based optical materials and devices.

Highlights

Optical devices have been fabricated so that their structure, material and, designed function would either remain unchanged with time, being virtually immutable, or could undergo changes only due to external adaptations of their constructs. This design strategy ensures a practically constant performance as a function of time within the individual components’ functional lifetime; it is based on materials whose properties have been highly engineered to fulfill one specific aim and are, optically, of very high quality [1]. This approach is very advantageous for the fabrication of optical devices that require high specialization and long durability; despite this, optical components built following this design strategy are strongly limited in multifunctionality and often lack inherent physical/chemical sensitivity and specificity to analytes, as they are programmed not to change
The past decade has witnessed a continuous growth in the development of silk-based stimuli-responsive optical devices, including reconfigurable photonic crystals, reversibly tunable optical structures, and physically transient devices
In spite of the opportunities enabled by the conformational transitions of silk, some critical questions remain unanswered: (i) how to fabricate “structurally patterned” silk matrices with high resolution over large areas; (ii) how to spatially and precisely control the protein’s conformation in thick structures

Summary

Introduction

Optical devices have been fabricated so that their structure, material and, designed function would either remain unchanged with time, being virtually immutable, or could undergo changes only due to external adaptations of their constructs. This design strategy ensures a practically constant performance as a function of time within the individual components’ functional lifetime; it is based on materials whose properties have been highly engineered to fulfill one specific aim and are, optically, of very high quality [1]. We comment on new research possibilities that can be enabled by silk’s variable properties

Silk for active optics

Reconfigurable optics

Reversibly tunable optics

Physically transient optics

Conclusion and outlook