A rewritable optical storage medium of silk proteins using near-field nano-optics

Decoding of compressive data pages for optical data storage utilizing FFDNet

Coded aperture-based compression has proven to be an effective approach for high-density cold data storage. Nevertheless, its limited decoding speed represents a significant challenge for its broader application. We introduce a novel, to the best of our knowledge, decoding method leveraging the fast and flexible denoising network (FFDNet), capable of decoding a coded aperture-based compressive data page within 30.64 s. The practicality of the method has been confirmed in the decoding of monochromatic photo arrays, full-color photos, and dynamic videos. In experimental trials, the variance between decoded results obtained via the FFDNet-based method and the FFDNet-absent method in terms of average PSNR is less than 1 dB, while realizing a decoding speed enhancement of over 100-fold when employing the FFDNet-based method.

Decoding silkworm spinning programmed by pH and metal ions

Silk is one of the toughest fibrous materials known despite spun at ambient temperature and pressure with water as a solvent. It is a great challenge to reproduce high-performance artificial fibers comparable to natural silk by bionic for the incomplete understanding of silkworm spinning in vivo. Here, we found that amphipol and digitonin stabilized the structure of natural silk fibroin (NSF) by a large-scale screening in vitro, and then studied the close-to-native ultrastructure and hierarchical assembly of NSF in the silk gland lumen. Our study showed that NSF formed reversible flexible nanofibrils mainly composed of random coils with a sedimentation coefficient of 5.8 S and a diameter of about 4 nm, rather than a micellar or rod-like structure assembled by the aggregation of globular NSF molecules. Metal ions were required for NSF nanofibril formation. The successive pH decrease from posterior silk gland (PSG) to anterior silk gland (ASG) resulted in a gradual increase in NSF hydrophobicity, thus inducing the sol-gelation transition of NSF nanofibrils. NSF nanofibrils were randomly dispersed from PSG to ASG-1, and self-assembled into anisotropic herringbone patterns at ASG-2 near the spinneret ready for silkworm spinning. Our findings reveal the controlled self-assembly mechanism of the multi-scale hierarchical architecture of NSF from nanofibrils to herringbone patterns programmed by metal ions and pH gradient, which provides novel insights into the spinning mechanism of silk-secreting animals and bioinspired design of high-performance fibers.

A supramolecular polymer network constructed using a pillararene-based multi-functional monomer and its application as a rewritable fluorescent paper

A simple and mild stimulus-responsive fluorescent supramolecular polymer network was constructed from a pillararene-based multi-functional monomer through multiple noncovalent interactions and used as a rewritable paper.

Fabrication of a VO2-Based Tunable Metasurface by Electric-Field Scanning Probe Lithography with Precise Depth Control

Vanadium dioxide (VO₂) is widely employed in developing tunable optoelectronic devices due to its significant changes in optical and electric properties upon phase transition. To fabricate the VO₂-based functional devices down to the micro/nanoscale, a high-resolution processing technique is in demand. Scanning probe lithography (SPL) on the basis of a tip-induced electric field provides a promising approach for prototyping. Here, we demonstrated a precise VO₂ etching strategy by direct writing on a VO₂ film with a negative tip bias and subsequent sonication removal of the written area. The effects of bias voltage, sonication, and thermal treatment as well as the mechanical difference between the tip-modulated area and the pristine VO₂ film were investigated systematically. The results show that VO₂ can be etched layer by layer via alternately repeating tip modulation and sonication, and arbitrary patterns can be written. Based on this route, we designed a kind of metasurface by arranging VO₂-gold nanoblocks with different sizes and heights for spectrally selective tunable reflectivity in near- and mid-infrared. This electric-field SPL method demonstrates the prominent advantages of high resolution down to several tens of nanometers, quasi-3D patterning, and resist-free maskless direct writing, which should be applicable for prototyping other micro/nanodevices.

All-Water Etching-Free Electron Beam Lithography for On-Chip Nanomaterials

Electron beam lithography uses an accelerated electron beam to fabricate patterning on an electron-beam-sensitive resist but requires complex dry etching or lift-off processes to transfer the pattern to the substrate or film on the substrate. In this study, etching-free electron beam lithography is developed to directly write a pattern of various materials in all-water processes, achieving the desired semiconductor nanopatterns on a silicon wafer. Introduced sugars are copolymerized with metal ions-coordinated polyethylenimine under the action of electron beams. The all-water process and thermal treatment result in nanomaterials with satisfactory electronic properties, indicating that diverse on-chip semiconductors (e.g., metal oxides, sulfides, and nitrides) can be directly printed on-chip by an aqueous solution system. As a demonstration, zinc oxide patterns can be achieved with a line width of 18 nm and a mobility of 3.94 cm² V^-1 s^-1. This etching-free electron beam lithography strategy provides an efficient alternative for micro/nanofabrication and chip manufacturing.

Engineering Silk Protein to Modulate Polymorphic Transitions for Green Lithography Resists

Silk protein is being increasingly introduced as a prospective material for biomedical devices. However, a limited locus to intervene in nature-oriented silk protein makes it challenging to implement on-demand functions to silk. Here, we report how polymorphic transitions are related with molecular structures of artificially synthesized silk protein and design principles to construct a green-lithographic and high-performative protein resist. The repetition number and ratio of two major building blocks in synthesized silk protein are essential to determine the size and content of β-sheet crystallites, and radicals resulting from tyrosine cleavages by the 193 nm laser irradiation induce the β-sheet to α-helix transition. Synthesized silk is designed to exclusively comprise homogeneous building blocks and exhibit high crystallization and tyrosine-richness, thus constituting an excellent basis for developing a high-performance deep-UV photoresist. Additionally, our findings can be conjugated to design an electron-beam resist governed by the different irradiation-protein interaction mechanisms. All synthesis and lithography processes are fully water-based, promising green lithography. Using the engineered silk, a nanopatterned planar color filter showing the reduced angle dependence can be obtained. Our study provides insights into the industrial scale production of silk protein with on-demand functions.

Highly sensitive photopolymer for holographic data storage

The insufficient photosensitivity of conventional organic recording materials such as phenanthraquinone-doped poly(methyl methacrylate) (PQ/PMMA) significantly limits the recording speed in holographic data storage. Accelerating the formation of free radicals using the photosensitizer PQ during the photoreaction process and increasing the C = C double bond concentration of the matrix are effective methods for improving the photosensitivity. Using the above methods, we doped PQ/PMMA with the co-photoinitiator triethanolamine and co-monomer acrylamide to improve the photosensitivity of the material. Compared with the original PQ/PMMA material, the photosensitivity was increased by 10 times, and the diffraction efficiency was increased by 20%. The role of each doping component was studied by characterization and analysis. In addition, the introduction of the cross-linking agent N,N'-methylene-bisacrylamide, having high sensitivity, reduced the shrinkage of the material. We verified the application of the new material in a collinear system, and its high sensitivity showed its great potential for holographic data storage.

Supertough and Highly Stretchable Silk Protein-based Films with Controlled Biodegradability

Naturally derived protein-based biopolymers are considered potential biomaterials in biomedical applications and eco-friendly materials for replacing current petroleum-based polymers due to their good biocompatibility, low environmental impact, and tunable degradability. However, current strategies for fabricating protein-based materials with superior properties and tailored functionality in a scalable manner are still lacking. Here, we demonstrate an aqueous-based scalable approach for fabricating silk protein-based films through controlled molecular self-assembly (CMS) of silk proteins with plasticizers and salt ions. The films fabricated using this method can achieve a toughness of up to 64±5 MJ/m³ with a stretchability of up to 574±31%. We also demonstrate the tunable enzymatic degradability, low in vitro cytotoxicity, and good in vivo biocompatibility of the films. Furthermore, the films can be patterned with predesigned complex structures through laser cutting and functionalized with bioactive components. The functional silk protein-based films show great potential in various applications, including flexible electronics, bioelectronics, tissue engineering, and bioplastic packaging. STATEMENT OF SIGNIFICANCE: Inspired by the naturally optimized multi-scale self-assembly of silk proteins in natural silks, we develop an aqueous-based approach for scalable production of superior protein-based films through controlled molecular self-assembly (CMS) of silk proteins with glycerol and calcium ions. The prepared silk films present outstanding mechanical properties, controlled enzymatic biodegradability, low in vitro cytotoxicity, and good in vivo biocompatibility. Notably, the films fabricated using this method can achieve a high toughness of 64±5 MJ/m³ with a stretchability of 594±31%. The approach introduced in this work provides a facile route toward making silk-based materials with superior properties. It also paves new avenues for developing functional protein-based materials with precisely controlled structures and properties for various applications.

Far-Field and Non-Intrusive Optical Mapping of Nanoscale Structures

Far-field high-density optics storage and readout involve the interaction of a sub-100 nm beam profile laser to store and retrieve data with nanostructure media. Hence, understanding the light–matter interaction responding in the far-field in such a small scale is essential for effective optical information processing. We present a theoretical analysis and an experimental study for far-field and non-intrusive optical mapping of nanostructures. By a comprehensive analytical derivation for interaction between the modulated light and the target in a confocal laser scanning microscopy (CLSM) configuration, it is found that the CLSM probes the local density of states (LDOSs) in the far field rather than the sample geometric morphology. With a radially polarized (RP) light for illumination, the far-field mapping of LDOS at the optical resolution down to 74 nm is obtained. In addition, it is experimentally verified that the target morphology is mapped only when the far-field mapping of LDOS coincides with the geometric morphology, while light may be blocked from entering the nanostructures medium with weak or missing LDOS, hence invalidating high-density optical information storage and retrieval. In this scenario, nanosphere gaps as small as 33 nm are clearly observed. We further discuss the characterization for far-field and non-intrusive interaction with nanostructures of different geometric morphology and compare them with those obtainable with the projection of near-field LDOS and scanning electronic microscopic results.

A Hierarchically Encoded Data Storage Device with Controlled Transiency

In the era of information explosion, high-security and high-capacity data storage technology attracts more and more attention. Physically transient electronics, a form of electronics that can physically disappear with precisely controlled degradation behaviors, paves the way for secure data storage. Herein, the authors report a silk-based hierarchically encoded data storage device (HEDSD) with controlled transiency. The HEDSD can store electronic, photonic, and optical information simultaneously by synergistically integrating a resistive switching memory (ReRAM), a terahertz metamaterial device, and a diffractive optical element, respectively. These three data storage units have shared materials and structures but diverse encoding mechanisms, which increases the degree of complexity and capacity of stored information. Silk plays an important role as a building material in the HEDSD thanks to its excellent mechanical, optical, and electrical properties and controlled transiency as a naturally extracted protein. By controlling the degradation rate of storage units of the silk-based HEDSD, different degradation modes of the HEDSD, and multilevel information encryption/decryption have been realized. Compared with the conventional memory devices, as-reported silk-based HEDSD can store multilevel complex information and realize multilevel information encryption and decryption, which is highly desirable to fulfill the future demands of secure memory systems and implantable storage devices.

Scattering-type Scanning Near-Field Optical Microscopy of Polymer-Coated Gold Nanoparticles

Scattering-type scanning near-field optical microscopy (s-SNOM) has emerged over the past years as a powerful characterization tool that can probe important properties of advanced materials and biological samples in a label-free manner, with spatial resolutions lying in the nanoscale realm. In this work, we explore such usefulness in relationship with an interesting class of materials: polymer-coated gold nanoparticles (NPs). As thoroughly discussed in recent works, the interplay between the Au core and the polymeric shell has been found to be important in many applications devoted to biomedicine. We investigate bare Au NPs next to polystyrenesulfonate (PSS) and poly(diallyldimethylammonium chloride) (PDDA) coated ones under 532 nm laser excitation, an wavelength matching the surface plasmon band of the custom-synthesized nanoparticles. We observe consistent s-SNOM phase signals in the case of bare and shallow-coated Au NPs, whereas for thicker shell instances, these signals fade. For all investigated samples, the s-SNOM amplitude signals were found to be very weak, which may be related to reduced scattering efficiency due to absorption of the incident beam. We consider these observations important, as they may facilitate studies and applications in nanomedicine and nanotechnology where the precise positioning of polymer-coated Au NPs with nanoscale resolution is needed besides their dielectric function and related intrinsic optical properties, which are also quantitatively available with s-SNOM.

In situ infrared nanospectroscopy of the local processes at the Li/polymer electrolyte interface

Solid-state batteries possess the potential to significantly impact energy storage industries by enabling diverse benefits, such as increased safety and energy density. However, challenges persist with physicochemical properties and processes at electrode/electrolyte interfaces. Thus, there is great need to characterize such interfaces in situ, and unveil scientific understanding that catalyzes engineering solutions. To address this, we conduct multiscale in situ microscopies (optical, atomic force, and infrared near-field) and Fourier transform infrared spectroscopies (near-field nanospectroscopy and attenuated total reflection) of intact and electrochemically operational graphene/solid polymer electrolyte interfaces. We find nanoscale structural and chemical heterogeneities intrinsic to the solid polymer electrolyte initiate a cascade of additional interfacial nanoscale heterogeneities during Li plating and stripping; including Li-ion conductivity, electrolyte decomposition, and interphase formation. Moreover, our methodology to nondestructively characterize buried interfaces and interphases in their native environment with nanoscale resolution is readily adaptable to a number of other electrochemical systems and battery chemistries.

Solid-state batteries remain promising but essential insights into electrode-electrolyte interface are required. Here, the authors report in situ infrared nanospectroscopy of the lithium-polymer-electrolyte interface to reveal its intrinsic molecular, structural, and chemical heterogeneities.

Super-resolution mid-infrared spectro-microscopy of biological applications through tapping mode and peak force tapping mode atomic force microscope

Small biomolecules at the subcellular level are building blocks for the manifestation of complex biological activities. However, non-intrusive in situ investigation of biological systems has been long daunted by the low spatial resolution and poor sensitivity of conventional light microscopies. Traditional infrared (IR) spectro-microscopy can enable label-free visualization of chemical bonds without extrinsic labeling but is still bound by Abbe's diffraction limit. This review article introduces a way to bypass the optical diffraction limit and improve the sensitivity for mid-IR methods - using tip-enhanced light nearfield in atomic force microscopy (AFM) operated in tapping and peak force tapping modes. Working principles of well-established scattering-type scanning near-field optical microscopy (s-SNOM) and two relatively new techniques, namely, photo-induced force microscopy (PiFM) and peak force infrared (PFIR) microscopy, will be briefly presented. With ∼ 10-20 nm spatial resolution and monolayer sensitivity, their recent applications in revealing nanoscale chemical heterogeneities in a wide range of biological systems, including biomolecules, cells, tissues, and biomaterials, will be reviewed and discussed. We also envision several future improvements of AFM-based tapping and peak force tapping mode nano-IR methods that permit them to better serve as a versatile platform for uncovering biological mechanisms at the fundamental level.

Silk Microneedle Patch Capable of On-Demand Multidrug Delivery to the Brain for Glioblastoma Treatment

Glioblastoma (GBM) is the most common and aggressive primary brain tumor. Surgery followed by chemotherapy and radiotherapy remains the standard treatment strategy for GBM patients. However, challenges still exist when surgery is difficult or impossible to remove the tumor completely. Herein, the design, fabrication and application of a heterogenous silk fibroin microneedle (SMN) patch is reported for circumventing the blood-brain barrier and releasing multiple drugs directly to the tumor site for drug combination treatment. The biocompatible and biodegradable SMN patch can dissolve slowly over time, allowing the sustained release of multiple drugs at different doses. Furthermore, it can be triggered remotely to induce rapid drug delivery at a designated stage after implantation. In the GBM mouse models, two clinically relevant chemotherapeutic agents (thrombin and temozolomide) and targeted drug (bevacizumab) are loaded into the SMN patch with individually controlled release profiles. The drugs are spatiotemporally and sequentially delivered for hemostasis, anti-angiogenesis, and apoptosis of tumor cells. Device application is non-toxic and results in decreased tumor volume and increased survival rate in mice. The SMN patch with on-demand multidrug delivery has potential applications for the combined administration of therapeutic drugs for the clinical treatment of brain tumors when other methods are insufficient.

Fast Customization of Microneedle Arrays by Static Optical Projection Lithography

Customized microneedle arrays (CMNAs) hold great promise for precise transdermal delivery in a minimally invasive manner. Currently, the fast customization of microneedle arrays remains a great challenge. Here, we show a static optical projection lithography (SOPL) technology for fast 3D printing CMNAs. In this technology, the digital light is statically projected to induce the spatial polymerization of monomer solutions, and therefore microneedle formation can be precisely controlled by the intensity distribution of the projected light. The obtained CMNAs do not have the stair-like surface and layer-by-layer structure that are associated with the common 3D-printing technologies. This method enables fast fabrication of CMNAs with designed shape, size, and distribution in seconds without mechanical motion system. Up-conversion nanoparticles (UCNPs) were delivered into skin by the CMNAs, to form a personalized dot matrix for in vivo information storage. Under the irradiation of near-infrared (NIR) light, the UCNPs in skin displayed a visible dot matrix, presenting information encoded in the structure of CMNAs. This work demonstrates a SOPL technology for rapidly customizing high-quality microneedle arrays and a CMNA-mediated in vivo information storage strategy.

Deep learning enhanced terahertz imaging of silkworm eggs development

Terahertz (THz) technology lays the foundation for next-generation high-speed wireless communication, nondestructive testing, food safety inspecting, and medical applications. When THz technology is integrated by artificial intelligence (AI), it is confidently expected that THz technology could be accelerated from the laboratory research stage to practical industrial applications. Employing THz video imaging, we can gain more insights into the internal morphology of silkworm egg. Deep learning algorithm combined with THz silkworm egg images, rapid recognition of the silkworm egg development stages is successfully demonstrated, with a recognition accuracy of ∼98.5%. Through the fusion of optical imaging and THz imaging, we further improve the AI recognition accuracy of silkworm egg development stages to ∼99.2%. The proposed THz imaging technology not only features the intrinsic THz imaging advantages, but also possesses AI merits of low time consuming and high recognition accuracy, which can be extended to other application scenarios.

3D electron-beam writing at sub-15 nm resolution using spider silk as a resist

Electron beam lithography (EBL) is renowned to provide fabrication resolution in the deep nanometer scale. One major limitation of current EBL techniques is their incapability of arbitrary 3d nanofabrication. Resolution, structure integrity and functionalization are among the most important factors. Here we report all-aqueous-based, high-fidelity manufacturing of functional, arbitrary 3d nanostructures at a resolution of sub-15 nm using our developed voltage-regulated 3d EBL. Creating arbitrary 3d structures of high resolution and high strength at nanoscale is enabled by genetically engineering recombinant spider silk proteins as the resist. The ability to quantitatively define structural transitions with energetic electrons at different depths within the 3d protein matrix enables polymorphic spider silk proteins to be shaped approaching the molecular level. Furthermore, genetic or mesoscopic modification of spider silk proteins provides the opportunity to embed and stabilize physiochemical and/or biological functions within as-fabricated 3d nanostructures. Our approach empowers the rapid and flexible fabrication of heterogeneously functionalized and hierarchically structured 3d nanocomponents and nanodevices, offering opportunities in biomimetics, therapeutic devices and nanoscale robotics.

Emerging Silk Material Trends: Repurposing, Phase Separation and Solution-Based Designs

Silk continues to amaze. This review unravels the most recent progress in silk science, spanning from fundamental insights to medical silks. Key advances in silk flow are examined, with specific reference to the role of metal ions in switching silk from a storage to a spinning state. Orthogonal thermoplastic silk molding is described, as is the transfer of silk flow principles for the triggering of flow-induced crystallization in other non-silk polymers. Other exciting new developments include silk-inspired liquid-liquid phase separation for non-canonical fiber formation and the creation of "silk organelles" in live cells. This review closes by examining the role of silk fabrics in fashioning facemasks in response to the SARS-CoV-2 pandemic.

Template-less Synthesis of Coded Au Nanowires

Morphological coding of nanostructures represents a capability in rapid modulation of structural features and most importantly, the transcription of information into nanoscale. Exploiting the regioselectivity in the template-less electrochemical synthesis of ultrathin Au nanowires, we show that rapid alternation of applied potential would cause corresponding change in the width of the emerging nanowire segments. By understanding the growth kinetics, a strong correlation between the nanowire morphologies and the deposition potential is established and applied in emulating the Morse code.