Artificial muscles may accelerate the development of robotics, haptics, and prosthetics. Although advances in polymer-based actuators have delivered unprecedented strengths, producing these devices at scale with tunable dimensions remains a challenge. We applied a high-throughput iterative fiber-drawing technique to create strain-programmable artificial muscles with dimensions spanning three orders of magnitude. These fiber-based actuators are thermally and optically controllable, can lift more than 650 times their own weight, and withstand strains of >1000%. Integration of conductive nanowire meshes within these fiber-based muscles offers piezoresistive strain feedback and demonstrates long-term resilience across >10 5 deformation cycles. The scalable dimensions of these fiber-based actuators and their strength and responsiveness may extend their impact from engineering fields to biomedical applications.

Nanowires are arguably the most studied nanomaterial model to make functional devices and arrays. Although there is remarkable maturity in the chemical synthesis of complex nanowire structures, their integration and interfacing to macro systems with high yields and repeatability still require elaborate aligning, positioning and interfacing and post-synthesis techniques. Top-down fabrication methods for nanowire production, such as lithography and electrospinning, have not enjoyed comparable growth. Here we report a new thermal size-reduction process to produce well-ordered, globally oriented, indefinitely long nanowire and nanotube arrays with different materials. The new technique involves iterative co-drawing of hermetically sealed multimaterials in compatible polymer matrices similar to fibre drawing. Globally oriented, endlessly parallel, axially and radially uniform semiconducting and piezoelectric nanowire and nanotube arrays hundreds of metres long, with nanowire diameters less than 15 nm, are obtained. The resulting nanostructures are sealed inside a flexible substrate, facilitating the handling of and electrical contacting to the nanowires. Inexpensive, high-throughput, multimaterial nanowire arrays pave the way for applications including nanowire-based large-area flexible sensor platforms, phase-changememory, nanostructure-enhanced photovoltaics, semiconductor nanophotonics, dielectric metamaterials,linear and nonlinear photonics and nanowire-enabled high-performance composites.

We produced kilometer-long, endlessly parallel, spontaneously piezoelectric and thermally stable poly(vinylidene fluoride) (PVDF) micro- and nanoribbons using iterative size reduction technique based on thermal fiber drawing. Because of high stress and temperature used in thermal drawing process, we obtained spontaneously polar γ phase PVDF micro- and nanoribbons without electrical poling process. On the basis of X-ray diffraction (XRD) analysis, we observed that PVDF micro- and nanoribbons are thermally stable and conserve the polar γ phase even after being exposed to heat treatment above the melting point of PVDF. Phase transition mechanism is investigated and explained using ab initio calculations. We measured an average effective piezoelectric constant as -58.5 pm/V from a single PVDF nanoribbon using a piezo evaluation system along with an atomic force microscope. PVDF nanoribbons are promising structures for constructing devices such as highly efficient energy generators, large area pressure sensors, artificial muscle and skin, due to the unique geometry and extended lengths, high polar phase content, high thermal stability and high piezoelectric coefficient. We demonstrated two proof of principle devices for energy harvesting and sensing applications with a 60 V open circuit peak voltage and 10 μA peak short-circuit current output. (Figure Presented). © 2014 American Chemical Society

separated, there are positive and negative charges generated on coated electrodes depending on the triboelectric polarity of those dielectric materials. Therefore, a perfect design for a triboelectric nanogenerator (TENG) can be achieved by choosing the most distinct materials in terms of triboelectric polarity as well as diminishing of the feature sizes of those materials down to nanometer scale for obtaining maximum contact area. [ 20 ] A list of the triboelectric materials in accordance with their polarity is presented in Table S1, Supporting Information. Working mechanisms of TENG devices are based on two mechanical motion modes, contact and sliding mode. [ 20 ] Recent studies reveal that the sliding mode has a better voltage output. [ 13 ] However, it requires a more complicated device design. The output voltage of TENGs is enhanced above 1 kV by using different material combinations and device geometries. [ 12 ] In this study, we constructed core-shell nanostructures (polyethersulfone (PES) is in the core and As 2 Se 3 is in the shell) for building a 3D TENG device ( Figure 1 a-6,a-7). Aluminum tape was used as a substrate and contact electrode for both polyetherimide (PEI) nanopillars and As 2 Se 3 core-shell nanostructures (Figure 1 a-1,a-5). Detailed information about the fabrication of the As 2 Se 3 core-shell nanostructures and the PEI nanopillars is given in the Supporting Information (see Figure S1). The fl uorination process used in the fabrication of the PEI nanopillars and surface modifi cation of the As 2 Se 3 nanostructures is given in Figure S2 in the Supporting Information. Figure S3 in the Supporting Information illustrates the fabrication process of the nanopillars.Our device can be stimulated by both motion and acoustic waves at different frequencies. We combined fl uorinated As 2 Se 3 kilometer-long core-shell nanostructures, which are produced using an iterative fi ber-drawing technique, with PEI nanopillars, which are produced by a template-based method for the construction of the contact mode TENG in a multilayer fashion. Our device has an output of maximum 1.23 mW direct current (DC) and 0.51 W peak power and can power parallel connected 38 LEDs simultaneously. Our chalcogenide-based TENG has maximum 396 V and 1.6 mA peak-to-peak output voltage and current, respectively. In addition, a fi nite element model is developed to explain contact electrifi cation between core-shell nanostructures and nanopillars using COMSOL Multiphysics. A perfect match between analytically calculated open-circuit voltage (OCV) and OCV measurement for a single layer generator was presented.To enhance the performance of triboelectric devices, there are two important parameters that play a major role in the selection of material combinations: the surface properties and triboelectric polarity. [ 20 ] Since the surface properties can be modifi ed using various techniques, the triboelectric polarity is Scavenging waste energy is an alternative prominent solution, which may play an important role regarding the wor...

Fiber drawing enables scalable fabrication of multifunctional flexible fibers that integrate electrical, optical, and microfluidic modalities to record and modulate neural activity. Constraints on thermomechanical properties of materials, however, have prevented integrated drawing of metal electrodes with low‐loss polymer waveguides for concurrent electrical recording and optical neuromodulation. Here, two fabrication approaches are introduced: 1) an iterative thermal drawing with a soft, low melting temperature (Tm) metal indium, and 2) a metal convergence drawing with traditionally non‐drawable high Tm metal tungsten. Both approaches deliver multifunctional flexible neural interfaces with low‐impedance metallic electrodes and low‐loss waveguides, capable of recording optically‐evoked and spontaneous neural activity in mice over several weeks. These fibers are coupled with a light‐weight mechanical microdrive (1 g) that enables depth‐specific interrogation of neural circuits in mice following chronic implantation. Finally, the compatibility of these fibers with magnetic resonance imaging is demonstrated and they are applied to visualize the delivery of chemical payloads through the integrated channels in real time. Together, these advances expand the domains of application of the fiber‐based neural probes in neuroscience and neuroengineering.

No abstract

Cataloged from PDF version of article.This article introduces surface textured polymer fibers as a new platform for the fabrication of affordable microfluidic devices. Fibers are produced tens of meters-long at a time and comprise 20 continuous and ordered channels (equilateral triangle grooves with side lengths as small as 30 micrometers) on their surfaces. Extreme anisotropic spreading behavior due to capillary action along the grooves of fibers is observed after surface modification with polydopamine (PDA). These flexible fibers can be fixed on any surface - independent of its material and shape - to form three-dimensional arrays, which spontaneously spread liquid on predefined paths without the need for external pumps or actuators. Surface textured fibers offer high-throughput fabrication of complex open microfluidic channel geometries, which is challenging to achieve using current photolithography-based techniques. Several microfluidic systems are designed and prepared on either planar or 3D surfaces to demonstrate outstanding capability of the fiber arrays in control of fluid flow in both vertical and lateral directions. Surface textured fibers are well suited to the fabrication of flexible, robust, lightweight, and affordable microfluidic devices, which expand the role of microfluidics in a scope of fields including drug discovery, medical diagnostics, and monitoring food and water quality. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Integration of nanowires into functional devices with high yields and good reliability turned out to be a lot more challenging and proved to be a critical issue obstructing the wide application of nanowire-based devices and exploitation of their technical promises. Here we demonstrate a relatively easy macrofabrication of a nanowire-based imaging circuitry using a recently developed nanofabrication technique. Extremely long and polymer encapsulated semiconducting nanowire arrays, mass-produced using the iterative thermal drawing, facilitate the integration process; we manually aligned the fibers containing selenium nanowires over a lithographically defined circuitry. Controlled etching of the encapsulating polymer revealed a monolayer of nanowires aligned over an area of 1 cm 2 containing a 10 × 10 pixel array. Each light-sensitive pixel is formed by the contacting hundreds of parallel photoconductive nanowires between two electrodes. Using the pixel array, alphabetic characters were identified by the circuitry to demonstrate its imaging capacity. This new approach makes it possible to devise extremely large nanowire devices on planar, flexible, or curved substrates with diverse functionalities such as thermal sensors, phase change memory, and artificial skin.