Wet‐Spinning Fabrication of Flexible Conductive Composite Fibers from Silver Nanowires and Fibroin

High-performing fiber electrodes based on a gold-shelled silver nanowire framework for bioelectronics

Flexible fiber electrodes offer new opportunities for bioelectronics and are reliable in vivo applications, high flexibility, high electrical conductivity, and satisfactory biocompatibility are typically required. Herein, we present an all-metal flexible and biocompatible fiber electrode based on a metal nanowire hybrid strategy, i.e., silver nanowires were assembled on a freestanding framework, and further to render them inert, they were plated with a gold nanoshell. Our fiber electrodes exhibited a low modulus of ∼75 MPa and electrical conductivity up to ∼4.8 × 106 S m-1. They can resist chemical erosion with negligible leakage of biotoxic silver ions in the physiological environment, thus ensuring satisfactory biocompatibility. Finally, we demonstrated the hybrid fiber as a neural electrode that stimulated the sciatic nerve of a mouse, proving its potential for applications in bioelectronics.

Fabrication of robust silver plated conductive polyamide fibres based on tannic acid modification

A novel method for the preparation of silver plated conductive polyamide fibres (PA/Ag) based on tannic acid modification was reported in this work. The highly adhesive tannic acid was grafted onto the surface of sulphuric acid roughened polyamide fibres to sensitize the fibre. Then, the sensitized polyamide fibres were activated by low-concentration silver nitrate to form reactive centers. Chemical silver plating was finally carried out using silver ammonia solution with glucose. The surface morphology and chemical properties of the prepared polyamide fibres were analyzed and the surface resistance, fastness to washing, thermal decomposition properties, electrothermal properties, sensing properties and practical applications of the silver-plated polyamide fibres were also tested. The test results show that the prepared conductive fibres have excellent conductivity and stability, and have potential applications in flexible electronic devices and sensing fields.

Recent applications of electrical, centrifugal, and pressurised emerging technologies for fibrous structure engineering in drug delivery, regenerative medicine and theranostics

Advancements in technology and material development in recent years has led to significant breakthroughs in the remit of fiber engineering. Conventional methods such as wet spinning, melt spinning, phase separation and template synthesis have been reported to develop fibrous structures for an array of applications. However, these methods have limitations with respect to processing conditions (e.g. high processing temperatures, shear stresses) and production (e.g. non-continuous fibers). The materials that can be processed using these methods are also limited, deterring their use in practical applications. Producing fibrous structures on a nanometer scale, in sync with the advancements in nanotechnology is another challenge met by these conventional methods. In this review we aim to present a brief overview of conventional methods of fiber fabrication and focus on the emerging fiber engineering techniques namely electrospinning, centrifugal spinning and pressurised gyration. This review will discuss the fundamental principles and factors governing each fabrication method and converge on the applications of the resulting spun fibers; specifically, in the drug delivery remit and in regenerative medicine.

Nature-derived materials for the fabrication of functional biodevices

Nature provides an incredible source of inspiration, structural concepts, and materials toward applications to improve the lives of people around the world, while preserving ecosystems, and addressing environmental sustainability. In particular, materials derived from animal and plant sources can provide low-cost, renewable building blocks for such applications. Nature-derived materials are of interest for their properties of biodegradability, bioconformability, biorecognition, self-repair, and stimuli response. While long used in tissue engineering and regenerative medicine, their use in functional devices such as (bio)electronics, sensors, and optical systems for healthcare and biomonitoring is finding increasing attention. The objective of this review is to cover the varied nature derived and sourced materials currently used in active biodevices and components that possess electrical or electronic behavior. We discuss materials ranging from proteins and polypeptides such as silk and collagen, polysaccharides including chitin and cellulose, to seaweed derived biomaterials, and DNA. These materials may be used as passive substrates or support architectures and often, as the functional elements either by themselves or as biocomposites. We further discuss natural pigments such as melanin and indigo that serve as active elements in devices. Increasingly, combinations of different biomaterials are being used to address the challenges of fabrication and performance in human monitoring or medicine. Finally, this review gives perspectives on the sourcing, processing, degradation, and biocompatibility of these materials. This rapidly growing multidisciplinary area of research will be advanced by a systematic understanding of nature-inspired materials and design concepts in (bio)electronic devices.