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The preform-to-fiber thermal drawing of thermoplastic elastomers enables the fabrication of soft multi-material optical fibers with complex architectures. It offers unprecedented opportunities to realize complex soft optical fibers for transmission and sensing.

Fibers that harvest mechanical energy via the triboelectric effect are excellent candidates as power sources for wearable electronics and functional textiles. Thus far however, their fabrication remains complex, and exhibited performances are below the state-of-the-art of 2D planar configurations, making them impractical. Here, we demonstrate the scalable fabrication of micro-structured stretchable triboelectric fibers with efficiencies on par with planar systems. We use the thermal drawing process to fabricate advanced elastomer fibers that combine a micro-textured surface with the integration of several liquid metal electrodes. Such fibers exhibit high electrical outputs regardless of repeated large deformations, and can sustain strains up to 560%. They can also be woven into deformable machine-washable textiles with high electrical outputs up to 490 V, 175 nC. In addition to energy harvesting, we demonstrate self-powered breathing monitoring and gesture sensing capabilities, making this triboelectric fiber platform an exciting avenue for multi-functional wearable systems and smart textiles., Current triboelectric fibers suffer from complex fabrication schemes and relatively poor performance. Here the authors use a highly scalable thermal drawing process to make soft and resilient micro-structured triboelectric fibers and textiles with applications both as sensors and energy harvesters.

International audience

Stretchable optical and electronic fibers constitute increasingly important building blocks for a myriad of applications, particularly in robotics, soft prosthesis, surgical tools and implants, and smart medical textiles. The integration of multimaterial architectures and complex functionalities within soft fibers has however for a long time remained difficult to achieve, limiting the performance and functionalities of medical fibers and textiles. In this contribution, we will show how the thermal drawing process used to fabricate optical fibers, and traditionally associated with rigid glasses or thermoplastic, can be applied to a certain class of thermoplastic elastomers. We will demonstrate that optical polymers, liquid metals, and conductive polymer composites could be co-drawn with prescribed architectures within a thermoplastic elastomer cladding. This allowed us to successfully fabricate super-elastic fibers with complex optical as well as electronic functionalities relevant for a myriad of applications in health-care. We will show in particular how such fibers can be used as precise and robust pressure, strain or more generally deformation sensors that can be seamlessly integrated within surgical tools, prosthesis, fabrics or robots. We will also discuss their potential as advanced optical probes, regenerative scaffolds or stimulating implants. This work opens novel opportunities for sensing and monitoring, scaffolds and implants, medical robotics and personalized care.

International audience; A key point of Fifth Generation (5G) wireless networking will be the exploitation of higher frequency bands in the millimeter wave (mm-Wave) spectrum to provide unprecedented data rates to mobile users. In such a perspective, the PHYsical (PHY) layer design priorities should be reconsidered. In this paper, we investigate Constant-Envelope Multicarrier (CE-MC) waveforms for future adoption in mm-Wave 5G transmissions, namely: Constant-Envelope Orthogonal Frequency Division Multiplexing (CE-OFDM) and Constant-Envelope Single-Carrier OFDM (CE-SC-OFDM). These waveforms are obtained by imposing a nonlinear phase modulation to a real-valued OFDM and SC-OFDM signal, respectively. Thanks to their 0dB Peak-to-Average-Power Ratio, such unconventional signaling formats are insensitive to nonlinear distortions and allow to exploit the flexibility of conventional multicarrier systems together with augmented resilience against multipath fading and phase noise. CE-OFDM and CE-SC-OFDM have been assessed by means of computer simulations in a short-range mm-Wave 5G scenario, i.e., downlink transmission in outdoor picocells. Simulation results demonstrate that CE multicarrier waveforms enhance robustness and increase coverage and capacity in the proposed scenario, as compared to conventional OFDM and SC-OFDM counterparts.

Stretchable optical and electronic fibers constitute increasingly important building blocks for a myriad of emerging applications, such as smart textile, robotics, or medical implants. Yet, it remains challenging to fabricate efficient and advanced soft fiber-base devices in a simple and scalable way. Conventional fiber manufacturing methods, such as wet and dry spinning, or extrusion, are not well adapted to fabricate multi-material functional fibers. The preform-to-fiber thermal drawing technique on the other hand is an emerging powerful platform to fabricate multi-material fibers with complex architectures and functionalities. Thus far however, this fabrication approach has been restricted to rigid thermoplastic or glass fibers. In this contribution we will show how we could revisit the selection criteria for cladding materials compatible with the thermal drawing process. In particular, thanks to a deeper rheological characterization, we could identify thermoplastic elastomers that could be drawn from a solid preform at high viscosity. Subsequently, we will demonstrate that thermoplastics, metals, and conductive polymer composites could be co-drawn with prescribed architectures within thermoplastic elastomer cladding. This allowed us to successfully fabricate stretchable optical and electronic fibers that are used as precise and robust pressure and strain sensors, as well as soft and stretchable waveguides as we will show via concrete examples, the ability to thermally draw soft multi-material fibers open new opportunities not only for exploring new academic research directions, but also in industrializing fiber-based flexible and stretchable devices for applications in sensing, health care, robotics and smart textiles.

Elastic optical fiber and sensors are fabricated via thermal drawing by identifying the proper thermoplastic elastomers. It offers unprecedented opportunities to realize flexible and stretchable optical fiber sensors.

Stretchable multi-material optical fibers are fabricated via the thermal drawing technique by identifying the proper thermoplastic elastomers. It offers unprecedented opportunities to realize complex soft optical fiber sensors.

Electronic and photonic fiber devices that can sustain large elastic deformation are becoming key components in a variety of fields ranging from healthcare to robotics and wearable devices. The fabrication of highly elastic and functional fibers remains however challenging, which is limiting their technological developments. Simple and scalable fiber-processing techniques to continuously codraw different materials within a polymeric structure constitute an ideal platform to realize functional fibers and devices. Despite decades of research however, elastomeric materials with the proper rheological attributes for multimaterial fiber processing cannot be identified. Here, the thermal drawing of hundreds-of-meters long multimaterial optical and electronic fibers and devices that can sustain up to 500% elastic deformation is demonstrated. From a rheological and microstructure analysis, thermoplastic elastomers that can be thermally drawn at high viscosities (above 103 Pa s), allowing the encapsulation of a variety of microstructured, soft, and rigid materials are identified. Using this scalable approach, fiber devices combining high performance, extreme elasticity, and unprecedented functionalities, allowing novel applications in smart textiles, robotics, or medical implants, are demonstrated.

Mechanical sensing is a key functionality in soft electronics intended for applications in health monitoring, human–machine interactions and soft robotics. Current methods typically use intricate networks of sensors specific to one type of deformation and one point in space, which limits their sensing capabilities. An alternative approach to distributed sensing is electrical reflectometry, but it is challenging to build the necessary transmission lines out of soft materials. Here, we report the scalable fabrication of microstructured elastomeric fibres that integrate tens of liquid metal conductors and have the length and cross-sectional integrity necessary to successfully apply time-domain reflectometry. Our soft transmission lines allow the detection of the mode, magnitude and position of multiple simultaneous pressing and stretching events. Furthermore, as a result of the dynamically responsive conductors, the pressure sensitivity is improved by a factor of 200 compared to rigid line probes. By integrating a single soft transmission line with a single interface port into a larger fabric, our technique can be used to create an electronic textile that can decipher convoluted mechanical stimulation. A microstructured liquid metal fibre can be used as a soft transmission line probe for reflectometry, allowing electronic textiles to be created that can decipher convoluted mechanical stimulation.

Soft robots are envisioned as the next generation of safe biomedical devices in minimally invasive procedures. Yet, the difficulty of processing soft materials currently limits the size, aspect-ratio, manufacturing throughput, as well as, the design complexity and hence capabilities of soft robots. Multi-material thermal drawing is introduced as a material and processing platform to create soft robotic fibers imparted with multiple actuations and sensing modalities. Several thermoplastic and elastomeric material options for the fibers are presented, which all exhibit the rheological processing attributes for thermal drawing but varying mechanical properties, resulting in adaptable actuation performance. Moreover, numerous different fiber designs with intricate internal architectures, outer diameters of 700 mu m, aspect ratios of 10(3), and a fabrication at a scale of 10s of meters of length are demonstrated. A modular tendon-driven mechanism enables 3-dimensional (3D) motion, and embedded optical guides, electrical wires, and microfluidic channels give rise to multifunctionality. The fibers can perceive and autonomously adapt to their environments, as well as, probe electrical properties, and deliver fluids and mechanical tools to spatially distributed targets.