Semiconductor diodes are basic building blocks of modern computation, communications and sensing. As such, incorporating them into textile-grade fibres can increase fabric capabilities and functions,  to encompass, for example,  fabric-based communications or physiological monitoring. However, processing challenges have so far precluded the realization of semiconducting diodes of high quality in thermally drawn fibres. Here we demonstrate a scalable thermal drawing process of electrically connected diode fibres. We begin by constructing a macroscopic preform that hosts discrete diodes internal to the structure alongside hollow channels through which conducting copper or tungsten wires are fed. As the preform is heated and drawn into a fibre, the conducting wires approach the diodes until they make electrical contact, resulting in hundreds of diodes connected in parallel inside a single fibre. Two types of in-fibre device are realized: light-emitting and photodetecting p-i-n diodes. An inter-device spacing smaller than 20 centimetres is achieved, as well as light collimation and focusing by a lens designed in the fibre cladding. Diode fibres maintain performance throughout ten machine-wash cycles, indicating the relevance of this approach to apparel applications. To demonstrate the utility of this approach, a three-megahertz bi-directional optical communication link is established between two fabrics containing receiver-emitter fibres. Finally, heart-rate measurements with the diodes indicate their potential for implementation in all-fabric physiological-status monitoring systems. Our approach provides a path to realizing ever more sophisticated functions in fibres, presenting  the prospect of a fibre 'Moore's law' analogue  through the increase of device density and function in thermally drawn textile-ready fibres.

A promising path for introducing rapid modulation into fibres would be through the piezoelectric effect [10][11] . Embedding piezoelectric domains would allow fibres to be electrically actuated over broad frequencies on the one hand, and to function as sensitive broadband microphones on the other. However, fibres for the most part have been made of materials in the disordered glassy state precluding the crystalline symmetry requirements necessary for piezoelectricity.Recent progress in drawing of fibres made of a multiplicity of materials 12 present new opportunities for re-examining this challenge. With this approach, fibre materials are drawn from 3 preforms in a regime dominated by viscous forces allowing for internal low viscosity domains to be arranged in non-equilibrium cross sections confined by viscous glassy boundary layers. In fact constructing a piezoelectric fibre could be accomplished in a straightforward manner by assembling a preform made of a piezoelectric material poly(vinylidene fluoride) (PVDF) 13-14 , with metal electrodes and an insulating polymer, which would be followed by a thermal draw.The stress present during the fibre draw should in principle induce the non-polar α to the ferroelectric β phase transition in the PVDF layer 13,[15][16] . The process should yield many metres of fibre with built-in internal electrodes which could be utilized to establish the large electric field necessary for poling the PVDF layer. However, upon detailed examination a number of significant challenges and seemingly conflicting requirements arise. The necessity to utilize crystalline materials both for the piezoelectric layer and the electrical conductors leads to the formation of multiple adjacent low viscosity and high aspect ratio domains. These domains undergoing a reduction in cross sectional dimensions are susceptible to capillary breakup and mixing during fibre drawing due to flow instabilities. Layer thickness non-uniformity either in the lateral or in the longitudinal directions [17][18] precludes the formation of the coercive field needed for poling. Moreover, even if capillary breakup were kinetically averted and uniform sections of fibres were to emerge they would not exhibit piezoelectricity because the stress and strain conditions necessary to induce the thermodynamic phase transition in PVDF cannot be sustained in the fibre draw process.To address these challenges we choose to focus our attention on the ability to maintain geometric coherence and layer thickness uniformity. A viscous and conductive carbon-loaded poly(carbonate) (CPC) is used to confine the low viscosity crystalline piezoelectric layer during 4 the draw process. The CPC layers exhibit high viscosity (10 5~1 0 6 Pa·s) at the draw temperature and adequate conductivity (1~10 4 ohm·m) over the frequency range from DC to tens of MHz, thus facilitating short range (hundreds of microns) charge transport on length scales associated with the fibre cross section. Then a piezoelectric polymer which crystallizes into the appropriate phase...

Infrared (IR) fibers offer a versatile approach to guiding and manipulating light in the IR spectrum, which is becoming increasingly more prominent in a variety of scientific disciplines and technological applications. Despite well-established efforts on the fabrication of IR fibers in past decades, a number of remarkable breakthroughs have recently rejuvenated the field-just as related areas in IR optical technology are reaching maturation. In this review, we describe both the history and recent developments in the design and fabrication of IR fibers, including IR glass and single-crystal fibers, multimaterial fibers, and fibers that exploit the transparency window of traditional crystalline semiconductors. This interdisciplinary review will be of interest to researchers in optics and photonics, materials science, and electrical engineering.