Computational and experimental study on silk fibroin and silk fibroin polymer electrolyte for application in transient energy storage devices

Transient implantable medical bionics (TIMBs), such as, degradable and biocompatible batteries that disappear after their operation, are gaining attention because they potentially facilitate the deployment of novel instructive biomaterials for regenerative medicine. In the wider context, the generation of degradable electronics potentially addresses problems associated with electronic waste (E-waste) and these materials can influence biological processes in a controllable manner, (e.g. tissue regeneration and drug delivery via electrical stimulation). Implantable degradable and biocompatible batteries may be capable of satisfying the power requirements of some biomedical devices and then harmlessly degrading.1 Therefore, these batteries are of great interest and a number of different battery designs have been reported in the literature. In this work, Mg and Zn primary air batteries utilising a degradable and biocompatible polymer electrolyte (PE) (silk fibroin [SF] and choline nitrate [Ch]NO3] ionic liquid [IL]) is reported. The batteries detailed in this work offer up to 7.18 Wh L-1 and 3.89 Wh L-1, respectively, which is sufficient to power ultralow power devices (e.g. 10 to 1000 µW pacemakers).5 However, the chemistry that underpins the interactions and performance of the materials utilised in the batteries reported in the literature has yet to be fully explored. Therefore, classical molecular dynamics (MD) simulations have been employed to investigate the interactions between SF and water molecules which are essential to the functionality of the batteries detailed in this work.1 An alanine-glycine (Ala-Gly) crystal model is implemented to represent the SF11, 68 with 7.5 % water by weight, which is analogous to regenerated SF films.1, 116 The silk crystal structure, reported in this work, is in the silk I form (i.e. repeated β-turn type II conformation), because β-sheets are not the predominant secondary structure (ca. 26 %), instead, the 310-helix is the predominant secondary structure (ca. 37 %). Furthermore, the trajectory of water diffusion is reported to be anisotropic (diffusion is prominent along the X-axis of the crystal model) with a diffusivity calculated at 1.60x10-6 cm2 s-1 at 298 K. Similar results were observed for experimentally determined water diffusivity in SF films at 5.79x10-6 cm2 s-1 at 298 K, possessing 36 % β-sheet content. By drawing inspiration from experimental studies on degradable and biocompatible batteries in the literature and producing an appropriate computational model to represent the pertinent materials theoretically (and experimental validation of them), should result in an improved understanding of the science underpinning the interactions and performance of these devices. Thus, a greater control over these devices should be achieved and potentially enable new applications of transient energy storage devices

A Mini-Review of Shape-Memory Polymer-Based Materials:Stimuli-responsive shape-memory polymers

Shape-memory polymers (SMPs) enable the production of stimuli-responsive polymer-based materials with the ability to undergo a large recoverable deformation upon the application of an external stimulus. Academic and industrial research interest in the shape-memory effects (SMEs) of these SMP-based materials is growing for task-specific applications. This mini-review covers interesting aspects of SMP-based materials, their properties, how they may be investigated and highlights examples of the potential applications of these materials

Atomistic Simulation of Water Incorporation and Mobility in Bombyx mori Silk Fibroin

Bombyx mori silk fibroin (SF) is a biopolymer that can be processed into materials with attractive properties (e.g., biocompatibility and degradability) for use in a multitude of technical and medical applications (including textiles, sutures, drug delivery devices, tissue scaffolds, etc.). Utilizing the information from experimental and computational SF studies, a simplified SF model has been produced (alanine–glycine [Ala–Gly]n crystal structure), enabling the application of both molecular dynamic and density functional theory techniques to offer a unique insight into SF-based materials. The secondary structure of the computational model has been evaluated using Ramachandran plots under different environments (e.g., different temperatures and ensembles). In addition, the mean square displacement of water incorporated into the SF model was investigated: the diffusion coefficients, activation energies, most and least favorable positions of water, and trajectory of water diffusion through the SF model are obtained. With further computational study and in combination with experimental data, the behavior/degradation of SF (and similar biomaterials) can be elucidated. Consequently, greater control of the aforementioned technologies may be achieved and positively affect their potential applications

Mg/Zn metal-air primary batteries using silk fibroin-ionic liquid polymer electrolytes

Batteries are utilized in a multitude of devices encountered in our daily lives. Here we describe a comparative study of Magnesium-air and Zinc-air primary batteries using silk fibroin-ionic liquid polymer electrolytes (composed of Bombyx mori silk fibroin and choline nitrate). The ionic conductivity of the films was of the order of mS cm−1 which is sufficient to satisfy the conductivity requirements for many battery applications, the open circuit voltages (V) for the Mg 1:1 SF:IL and 1:3 SF:IL batteries just after fabrication were ca. 1.8 and 1.7 V, respectively; the 1:1 SF:IL battery had a capacity of 0.84 mAh cm−2, whereas the 1:3 SF:IL battery had a capacity of 0.68 mAh cm−2. The open circuit voltages (V) for the Zn 1:1 SF:IL and 1:3 SF:IL batteries were in the range of 1.3 and 1.2 V just after fabrication; the 1:3 SF:IL battery displayed a capacity of 0.96 mAh cm−2 and the 1:3 SF:IL battery displayed a capacity of 0.72 mAh cm−2. Integration of the PE and substitution of the carbon cloth electrodes with degradable materials would offer routes to production of transient primary batteries helping to address the global issue of electronic waste (e-waste)

Thermo-responsive and electroconductive shape-memory polymer composites for useful applications

Shape-memory polymers (SMPs) are stimuli-responsive materials with the ability to undergo a large recoverable deformation upon the application of an external stimulus. International research interest into the shape-memory effects (SMEs) of these polymers is rapidly growing. Unique polymer composites combining the properties of existing SMPs with electroconductive polymers (CPs) have been produced via direct laser writing or multiphoton fabrication (using a Photonic Nanoscribe). The modified SMPs will be reported for the first time, in addition, their properties are investigated and prove insightful for potential applications of these materials

Creating 3D objects with integrated electronics via multiphoton fabrication in vitro and in vivo

3D objects with integrated electronics were produced using an additive manufacturing approach relying on multiphoton fabrication (direct laser writing, DLW). Conducting polymer-based structures (with micrometer-millimeter scale features) were printed within exemplar matrices, including an elastomer (polydimethylsiloxane, PDMS) widely investigated for biomedical applications. The fidelity of the printing process in PDMS was assessed by optical coherence tomography, and the conducting polymer structures were demonstrated to be capable of stimulating mouse brain tissue in vitro. Furthermore, the applicability of the approach to printing structures in vivo was demonstrated in live nematodes (Caenorhabditis elegans). These results highlight the potential for such additive manufacturing approaches to produce next-generation advanced material technologies, notably integrated electronics for technical and medical applications (e.g., human-computer interfaces)

Creating 3D Objects with Integrated Electronics via Multiphoton Fabrication In Vitro and In Vivo

3D objects with integrated electronics are produced using an additive manufacturing approach relying on multiphoton fabrication (direct laser writing, (DLW)). Conducting polymer-based structures (with micrometer-millimeter scale features) are printed within exemplar matrices, including an elastomer (polydimethylsiloxane, (PDMS)) have been widely investigated for biomedical applications. The fidelity of the printing process in PDMS is assessed by optical coherence tomography, and the conducting polymer structures are demonstrated to be capable of stimulating mouse brain tissue in vitro. Furthermore, the applicability of the approach to printing structures in vivo is demonstrated in live nematodes (Caenorhabditis elegans). These results highlight the potential for such additive manufacturing approaches to produce next-generation advanced material technologies, notably integrated electronics for technical and medical applications (e.g., human-computer interfaces)