Chip-on-tip endoscope incorporating a soft robotic pneumatic bending microactuator.

In the ever advancing field of minimally invasive surgery, flexible instruments with local degrees of freedom are needed to navigate through the intricate topologies of the human body. Although cable or concentric tube driven solutions have proven their merits in this field, they are inadequate for realizing small bending radii and suffer from friction, which is detrimental when automation is envisioned. Soft robotic actuators with locally actuated degrees of freedom are foreseen to fill in this void, where elastic inflatable actuators are very promising due to their S3-principle, being Small, Soft and Safe. This paper reports on the characterization of a chip-on-tip endoscope, consisting out of a soft robotic pneumatic bending microactuator equipped with a 1.1 × 1.1 mm2 CMOS camera. As such, the total diameter of the endoscope measures 1.66 mm. To show the feasibility of using this system in a surgical environment, a preliminary test on an eye mock-up is conducted

Fabrication of planar colloidal clusters with template-assisted interfacial assembly.

The synthesis of nanoparticle clusters, also referred to as colloidal clusters or colloidal molecules, is being studied intensively as a model system for small molecule interactions as well as for the directed self-assembly of advanced materials. This paper describes a technique for the interfacial assembly of planar colloidal clusters using a combination of top-down lithographic surface modification and bottom-up Langmuir-Blodgett deposition. Micrometer sized polystyrene latex particles were deposited onto a chemically modified substrate from a decane-water interface with Langmuir-Blodgett deposition. The surface of the substrate contained hydrophilic domains of various size, spacing, and shape, while the remainder of the substrate was hydrophobic. Particles selectively deposited onto hydrophilic regions from the decane-water interface. The number of deposited particles depended on the size of each patch, thereby demonstrating that tuning cluster size is possible by engineering patch geometry. Following deposition, the clusters were permanently bonded with temperature annealing and then removed from the substrate via sonication. The permanently bonded planar colloidal clusters were stable in an aqueous environment and at a decane-water interface laden with isotropic colloidal particles. The method is a simple and fast way to synthesize colloidal clusters with few limitations on particle chemistry, composition, and shape.The authors thank Professor Luis M. Liz-Marzan, head of the Colloidal Chemistry Group at Universidade de Vigo, Spain, for the gold nanorod suspension. The research was performed as part of the IAP program MICROMAST financed by BELSPO. The FWO Vlaanderen, projects G.0554.10 and G.0697.11, as well as the ERC starting grant 337739 - HIENA are gratefully acknowledged for their financial support.This is the accepted manuscript. The final version is available from ACS at http://pubs.acs.org/doi/abs/10.1021/la504383m

Light Rechargeable Lithium-ion Batteries Using V2O5 Cathodes

Solar energy is one of the most actively pursued renewable energy sources, but like many other sustainable energy sources, its intermittent character means solar cells have to be connected to an energy storage system to balance production and demand. To improve the efficiency of this energy conversion and storage process, photo-batteries have recently been proposed where one of the battery electrodes is made from a photo-active material that can directly be charged by light without using solar cells. Here, we present photo-rechargeable lithium-ion batteries (Photo-LIBs) using photocathodes based on vanadium pentoxide nanofibers mixed with P3HT and rGO additives. These photocathodes support the photo-charge separation and transportation process needed to recharge. The proposed Photo-LIBs show capacity enhancements of more than 57% under illumination and can be charged to ~ 2.82 V using light and achieve conversion efficiencies of ~ 2.6% for 455 nm illumination and ~ 0.22% for 1 sun illumination.Newton International Fellowship-Royal Society (UK) grant NIF∖R1∖181656 ERC Consolidator grant MIGHTY - 866005 EPSRC Graphene CDT EP/L016087/

Molybdenum Disulfide-Zinc Oxide Photocathodes for Photo-Rechargeable Zinc-Ion Batteries.

Systems for harvesting and storing solar energy have found practical applications ranging from solar farms to autonomous smart devices. Generally, these energy solutions consist of solar cells for light harvesting and rechargeable batteries to match the solar energy supply to consumption demands. Rather than having a separate energy harvesting and storing device, we report photo-rechargeable zinc-ion batteries (hν-ZIBs) using a photoactive cathode composed of layer-by-layer grown zinc oxide and molybdenum disulfide. These photocathodes are capable of harvesting solar energy and storing it in the same material and alleviate the need for solar cells or power converters. The proposed photocathodes achieve photoconversion efficiencies of ∼1.8% using a 455 nm light source and ∼0.2% of solar-conversion efficiencies. Light not only allows photocharging but also enhances the battery capacity from 245 to 340 mA h g-1 (specific current of 100 mA g-1 and 12 mW cm-2 light intensity at 455 nm). Finally, the proposed hν-ZIBs also demonstrate a capacity retention of ∼82% over 200 cycles

Hierarchical Assemblies of Carbon Nanotubes for Ultraflexible Li-Ion Batteries.

The flexible batteries that are needed to power flexible circuits and displays remain challenging, despite considerable progress in the fabrication of such devices. Here, it is shown that flexible batteries can be fabricated using arrays of carbon nanotube microstructures, which decouple stress from the energy-storage material. It is found that this battery architecture imparts exceptional flexibility (radius ≈ 300 μm), high rate (20 A g(-1) ), and excellent cycling stability.Engineering and Physical Sciences Research Council (Grant ID: EP/L025531/1)This is the author accepted manuscript. The final version is available from Wiley via http://dx.doi.org/10.1002/adma.20160091

Oxidative Degradation of Tetracycline by Magnetite and Persulfate: Performance, Water Matrix Effect, and Reaction Mechanism.

This study presents a strategy to remove tetracycline by using magnetite-activated persulfate. Magnetite (Fe3O4) was synthesized at high purity levels-as established via X-ray diffractometry, transmission electron microscopy, and N2 sorption analyses-and tetracycline was degraded within 60 min in the presence of both magnetite and persulfate (K2S2O8), while the use of either substance yielded limited degradation efficiency. The effects of magnetite and persulfate dosage, the initial concentration of tetracycline, and the initial pH on the oxidative degradation of tetracycline were interrogated. The results demonstrate that the efficiency of tetracycline removal increased in line with magnetite and persulfate dosage. However, the reaction rate increased only when increasing the magnetite dosage, not the persulfate dosage. This finding indicates that magnetite serves as a catalyst in converting persulfate species into sulfate radicals. Acidic conditions were favorable for tetracycline degradation. Moreover, the effects of using a water matrix were investigated by using wastewater treatment plant effluent. Comparably lower removal efficiencies were obtained in the effluent than in ultrapure water, most likely due to competitive reactions among the organic and inorganic species in the effluent. Increased concentrations of persulfate also enhanced removal efficiency in the effluent. The tetracycline degradation pathway through the magnetite/persulfate system was identified by using a liquid chromatograph-tandem mass spectrometer. Overall, this study demonstrates that heterogeneous Fenton reactions when using a mixture of magnetite and persulfate have a high potential to control micropollutants in wastewater

Precise Catalyst Production for Carbon Nanotube Synthesis with Targeted Structure Enrichment

The direct growth of single-walled carbon nanotubes (SWCNTs) with a narrow distribution of diameter or chirality remains elusive despite significant benefits in properties and applications. Nanoparticle catalysts are vital for SWCNT synthesis, but how to precisely manipulate their chemistry, size, concentration, and deposition remains difficult, especially within a continuous production process from the gas phase. Here, we demonstrate the preparation of W6Co7 alloyed nanoparticle catalysts with precisely tunable stoichiometry using electrospray, which remain solid state during SWCNT growth. We also demonstrate continuous production of liquid iron nanoparticles with in-line size selection. With the precise size manipulation of catalysts in the range of 1−5 nm, and a nearly monodisperse distribution (σg 1.2), an excellent size selection of SWCNTs can be achieved. All of the presented techniques show great potential to facilitate the realization of single-chirality SWCNTs production

Paper-Based Electrochemical Sensors Using Paper as a Scaffold to Create Porous Carbon Nanotube Electrodes.

Paper-based sensors and assays have evolved rapidly due to the conversion of paper-based microfluidics, functional paper coatings, and new electrical and optical readout techniques. Nanomaterials have gained substantial attraction as key components in paper-based sensors, as they can be coated or printed relatively easily on paper to locally control the device functionality. Here, we report a new combination of methods to fabricate carbon nanotube-based (CNT) electrodes for paper-based electrochemical sensors using a combination of laser cutting, drop-casting, and origami. We applied this process to a range of filter papers with different porosities and used their differences in three-dimensional cellulose networks to study the influence of the cellulose scaffold on the final CNT network and the resulting electrochemical detection of glucose. We found that an optimal porosity exists, which balances the benefits of surface enhancement and electrical connectivity within the cellulose scaffold of the paper-based device and demonstrates a cost-effective process for the fabrication of device arrays

Anisotropic Carbon Nanotube Structures with High Aspect Ratio Nanopores for Li-Ion Battery Anodes.

Technological advances in membrane technology, catalysis, and electrochemical energy storage require the fabrication of controlled pore structures at ever smaller length scales. It is therefore important to develop processes allowing for the fabrication of materials with controlled submicron porous structures. We propose a combination of colloidal lithography and chemical vapor deposition of carbon nanotubes to create continuous straight pores with diameters down to 100 nm in structures with thicknesses of more than 300 μm. These structures offer unique features, including continuous and parallel pores with aspect ratios in excess of 3000, a low pore tortuosity, good electrical conductivity, and electrochemical stability. We demonstrate that these structures can be used in Li-ion batteries by coating the carbon nanotubes with Si as an active anode material

Interrogating the Light-Induced Charging Mechanism in Li-Ion Batteries Using Operando Optical Microscopy

Photobatteries, batteries with a light-sensitive electrode, have recently been proposed as a way of simultaneously capturing and storing solar energy in a single device. Despite reports of photocharging with multiple different electrode materials, the overall mechanism of operation remains poorly understood. Here, we use operando optical reflection microscopy to investigate light-induced charging in LixV2O5 electrodes. We image the electrode, at the single-particle level, under three conditions: (a) with a closed circuit and light but no electronic power source (photocharging), (b) during galvanostatic cycling with light (photoenhanced), and (c) with heat but no light (thermal). We demonstrate that light can indeed drive lithiation changes in LixV2O5 while maintaining charge neutrality, possibly via a combination of faradaic and nonfaradaic effects taking place in individual particles. Our results provide an addition to the photobattery mechanistic model highlighting that both intercalation-based charging and lithium concentration polarization effects contribute to the increased photocharging capacity