Structural Protein-Based Whispering Gallery Mode Resonators

Abstract

Nature provides a set of solutions for photonic structures that are finely tuned, organically diverse, and optically efficient. Exquisite knowledge of structure−property relationships in proteins aids in the design of materials with desired properties for building devices with novel functionalities, which are difficult to achieve or previously unattainable.Here we report whispering-gallery-mode (WGM) microresonators fabricated entirely from semicrystalline structural proteins (i.e., squid ring teeth, SRT, from Loligo vulgaris and its recombinant) with quality factors as high as 10 5 . We first demonstrate versatility of protein-based devices via facile doping, engaging secondary structures. Then we investigate thermorefractivity and find that it increases with β-sheet crystallinity, which can be altered by methanol exposure and is higher in the selected recombinant SRT protein than its native counterpart. We present a set of photonic devices fabricated from SRT proteins such as add-drop filters and fibers. Protein-based microresonators demonstrated in this work are highly flexible and robust where quality factors and spectral position of resonances are unaffected from mechanical strain. We find that the thermooptic coefficients of SRT proteins are nearly 100× larger than silica and more than 10× larger than polydimethylsiloxane. Finally, we demonstrate an optical switch utilizing the surprisingly large thermorefractivity of SRT proteins. Achieving 41 dB isolation at an input power of 1.44 μW, all-protein optical switch is 10× more energy efficient than a conventional (silica) thermo-optic switch.

Composites of Proteins and 2D Nanomaterials

“…The amino acid sequence of proteins determines their secondary and tertiary structures; hence they provide a variety of structural conformations . Proteins can often self‐assemble in order to form natural materials with extraordinary properties such as extremely high durability or elasticity . Hence, designing new proteins using biotechnology tools has been an interest for materials scientists for modifying and assembling novel morphologies and molecular architectures .…”

“…Proteins can often self‐assemble in order to form natural materials with extraordinary properties such as extremely high durability or elasticity . Hence, designing new proteins using biotechnology tools has been an interest for materials scientists for modifying and assembling novel morphologies and molecular architectures . The amino acid sequences of the proteins can be controlled to prescribe the alignment of 2D layers that form the substrate of composites, ultimately dictating different functional properties (e.g., mechanical, optical, electrical, and thermal).…”

Squid-Inspired Tandem Repeat Proteins: Functional Fibers and Films

“…Ordered domains like β-sheet structures provide mechanical strength (e.g., SRT and silk fibroin are β-sheet-rich structural proteins with modulus in the GPa range), while disordered domains provide elasticity and flexibility to the material (e.g., similar to disordered resilin in the wing tendon of insects) (Cheng et al, 2010; Guerette et al, 2013; Yarger et al, 2018). The secondary structure content does not only influence the mechanical properties of SRT-based materials, but also their thermal (Jung et al, 2017), conducting (Pena-Francesch et al, 2018b), and optical properties (Yilmaz et al, 2016, 2017). The morphology of disordered domains also plays an important role in defining the bulk properties of protein-based SRT materials.…”

Dielectrophoretic separation of randomly shaped protein particles

“…By combining the concept of biomimicry and theoretical foundations of block copolymers, these structural motifs have been exploited to design protein-based materials with remarkable new properties. Many reports have shown that these new materials can have interesting and useful mechanical, optical, and thermal properties [4][5][6][7][8][9][10][11]. Moreover, tandem repeat proteins govern the assembly of composites materials such as graphene oxide and MXenes (Ti3C2Tx) for 2D layered structures as well as self-healing characteristics of conducting polymers for applications in flexible electronics and biocompatible electronics [12][13][14].…”