Research On Femtosecond Laser Direct Writing And Functionalities Of Protein-based Photonic Micro/Nano-devices

Protein is the important material basis of life activities. Owing to a long period ofnatural evolution, a variety of proteins are endowed with diverse molecular structures,properties and intrinsic functions, most of which are difficult to imitate and substituteby artificial materials. In recent years, various biomaterials based on proteins andtheir derivatives are organically combined with advanced micro/nano-precisionprocessing and integration technologies. Consequently, proteins (and derivatives) arewidely used as the important, key and even core materials to construct new-typemicro/nano-scale structures, components and integrated systems with variousfunctionalities. This has become one of the most significant edge-cutting directionsand trends of protein-based materials’ research and applications. In particular, thenovel applications of proteins and their derivatives are in the ascendant formultidisciplinary fields related to micro/nano-level optics and electronics. However,it might be the lack of true three-dimensional (3D) ability with sub-micron and evennano-scale precision that further micro/nano-level utilizations of protein-basedbiomaterials are greatly limited especially for3D optics and photonics. On the otherhand, many optical, photonic micro/nano-devices have been fabricated with various2D/3D geometries and high quality via femtosecond laser direct writing (FsLDW).However, most of them are based on traditional artificial materials like syntheticpolymers, and the prototyped functions generally rely more on different geometricstructures of devices. This largely hinders the multifunctionalzation ofFsLDW-fabricated photonic micro/nano-devices and their development in manyareas like sensing and bio-related engeering. To solve problems above, we useFsLDW to customize kinds of protein-based functionalized photonic micro/nano-devices in this paper. The main research contents are as follows:I. Protein-based functional lens micro-devices fabricated via FsLDW:1, for theprotein-based spherical microlenses and harmonic diffractive continuous reliefmicrolenses, the excellent device quality, optical properties, biocompatibility, andespecially the "smart" environment-responsive dynamic adjustment (such as pH, ionstrength) are achieved;2, on the premise of its good prototype optical properties, theprotein-based phase-diffractive microlenses have the features of immunity toenvironmental stilumi, flexibility including stretching and bending, andbiodegradability.II. FsLDW customization and functionalization of protein-based opticalwaveguide micro/nano-devices:1, the protein-based single-nanowire opticalwaveguides are proved of optical windows (~600nm) close to that of body tissuesand transmission light loss, as well as optical specific sensing via copolymerizationof "probe" proteins during FsLDW;2, flexible design and preparation of variousprotein-based multifunctional micro/nano-waveguide devices (such as multimodeinterference light-power microsplitters, Y-junction-based light-power microsplitters).III. protein-based whispering-gallery-mode (WGM) true-3D micro-lasers:1,high-quality protein-based WGM true-3D micro-disks are FsLDW-fabricated fromaqueous ink comprehensively relying on processing-parameter optimization,high-viscosity protein protogel, and "conformal" scanning mode;2, withoutpost-annealing, the protein-based WGM true-3D micro-lasers exhibit stable andhigh-Q (~3300) lasing action in air and aqueous environments, better thansynthetic-polymer-based similar devices;3, environmental stimuli responsive (e.g.,salt concentration) lasing peak wavelengths are experimentally demonstrated,IV. FsLDW customization of regenerated-silk-fibroin-centered (RSF, as"core-module" material) diverse functional micro/nano-devices:1, all-RSF-basedFsLDW multiphoton lithograpy is implemented, and obtained pure RSF2D/3Dmicro/nano-stuctures own mechanical strength much higher than otherFsLDW-prepared protein micro/nano-hydrogels (Young’s modulus,~2.2GPa in the air, and~0.22GPa in water);2, Femtosecond laser simultaneously inducescrosslinking of RSF and reduction and loading of metals, so that the RSF/silver andRSF/gold composite micro/nano-scale structures and devices are fabricated.Especially, the RSF/silver composite microwire show good electric conductivity withlong-term stability in air;3, the metal content in RSF/metal composites are"multi-dimensionally" controlled via reduction and loading with pre-exposure, pHvalue, and solution composition;4, ATR-FTIR characterizations of all kinds ofRSF-centered micro/nano-structures prove the β-folding crystallization of silk fibroinwhich causes the high mechanical strength; also, fluorescence property has beencharacterized;5, for the first time, the possible mechanism of silk-fibroin-basedFsLDW is proposed.In summary, in this paper, first of all, various high-quality2D and3Dprotein-based photonic/electric micro/nano-devices are constructed with sub-micronand even nano-level precision via protein-based FsLDW approach. Their prototypefunctions are well realized. Proteins are successfully utilized here as an idealeco/bio-compatible alternative of artificial synthetic polymers. Then, the obtainednovel devices are endowed with a variety of features and functions by fullyexcavating intrinsic properties of protein. Further, functions can be facilelycustomized for the protein-based photonic/electric micro/nano-devices by means ofblending, chemical modification and mineralization loading before, during or afterFsLDW. Consequently, the "double" designability and controllability are achieved onboth material properties and geometrical configuration of the protein-basedphotonic/electric micro/nano-devices to implement diverse features andfunctionalities, helping significantly to promote their diversified applications.