Customizing MRI-Compatible Multifunctional Neural Interfaces through Fiber Drawing.

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 we introduce two fabrication approaches: (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. We couple these fibers with a light-weight mechanical microdrive (1g) that enables depth-specific interrogation of neural circuits in mice following chronic implantation. Finally, we demonstrate the compatibility of these fibers with magnetic resonance imaging (MRI) and apply them 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.

Macroscopic assembly of indefinitely long and parallel nanowires into large area photodetection circuitry.

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.

High selectivity Boolean olfaction using hollow-core wavelength-scalable Bragg fibers.

A new odorant detection scheme, based on infrared absorption of volatile organics inside an optofluidic channel array, is discussed in terms of its selectivity. The sensor unit of the array is a hollow core Bragg fiber that selectively (spectrally) guides an incident continuum radiation. The presence of infrared absorbing molecules in the channel results in the quenching of the otherwise transmitted signal. Each fiber unit in the array is designed and fabricated so that it is sensitive to specific chemical bonds and the bond environment, but at the same time, each fiber is also broadly sensitive to a large number of chemicals due to their infrared absorbance spectra. The cumulative array response data, using an appropriate threshold, enable selective binary sampling of the infrared fingerprint of hundreds of molecules. The selectivity of the system is quantitatively investigated with computer simulations and found to be exponentially increasing with the number of fibers in the array. Relatively simple data analysis using binary logic combined with the high selectivity of the novel scheme paves the way for ubiquitous application of electronic noses in toxic gas detection, food quality control, environmental monitoring, and breath analysis for disease diagnostics.

Arrays of indefinitely long uniform nanowires and nanotubes.

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.

Pediatric Patients with COVID-19: A Retrospective Single-Center Experience.

Objectives: The pandemic of coronavirus disease 2019 (COVID-19) is still effective all over the world. Compared to adults, data on pediatric patients are limited. In this study, we aimed to retrospectively examine the demographic, clinical, and laboratory characteristics of pediatric patients who were followed up with the diagnosis of COVID-19 in the first 3 months of the pandemic in our hospital. Methods: A total of 190 patients, aged 1 month-18 years, who were followed up with a definite/probable diagnosis of COVID-19, who were treated in the Pediatric Infection Clinic, were included in the study. The demographic features, clinical characteristics, and laboratory findings of the patients were retrospectively analyzed from their electronic medical records. Results: Eighty (42.1%) of the patients were laboratory confirmed (Polymerase chain reaction positive in nasopharyngeal swab). Mean age was 72 (2-216 months) and 102 (53.7%) patients were female. Family contact history was present in 115 (60.5%) patients. The patients were classified as asymptomatic (5.8%), mild (73.2%), moderate (18.4%), and severe/critical (2.6%) according to the severity of the disease. The most common symptoms were cough (71.1%) and fever (51.1%). Hydroxychloroquine alone or in combination was the most commonly used agent. Conclusion: In our study, in which we examined the pediatric COVID-19 patients, most of the patients had a mild clinical course, but there were applications with different clinical pictures such as acute appendicitis. Therefore, COVID-19 infection, which is still very unknown, will continue to surprise us with both changing treatment protocols and clinical presentations such as multisystem inflammatory syndrome in children.

Selectively Micro-Patternable Fibers via In-Fiber Photolithography.

Multimaterial fibers engineered to integrate glasses, metals, semiconductors, and composites found applications in ubiquitous sensing, biomedicine, and robotics. The longitudinal symmetry typical of fibers, however, limits the density of functional interfaces with fiber-based devices. Here, thermal drawing and photolithography are combined to produce a scalable method for deterministically breaking axial symmetry within multimaterial fibers. Our approach harnesses a two-step polymerization in thiol-epoxy and thiol-ene photopolymer networks to create a photoresist compatible with high-throughput thermal drawing in atmospheric conditions. This, in turn, delivers meters of fiber that can be patterned along the length increasing the density of functional points. This approach may advance applications of fiber-based devices in distributed sensors, large area optoelectronic devices, and smart textiles.

Strain-programmable fiber-based artificial muscle.

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 >105 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.

A motion- and sound-activated, 3D-printed, chalcogenide-based triboelectric nanogenerator.

A multilayered triboelectric nanogenerator (MULTENG) that can be actuated by acoustic waves, vibration of a moving car, and tapping motion is built using a 3D-printing technique. The MULTENG can generate an open-circuit voltage of up to 396 V and a short-circuit current of up to 1.62 mA, and can power 38 LEDs. The layers of the triboelectric generator are made of polyetherimide nanopillars and chalcogenide core-shell nanofibers.

Spontaneous high piezoelectricity in poly(vinylidene fluoride) nanoribbons produced by iterative thermal size reduction technique.

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.