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Eric Klein, Christian Gossler, Oliver Paul, Patrick Ruther
This study reports the realization of an optical cochlear implant (oCI) with optimized thermomechanical properties for optogenetic experiments. The oCI probe comprises 144 miniaturized light-emitting diodes (μLEDs) distributed along a bendable, 1.5-cm-long, 350-μm-wide and 26-μm-thick probe shaft, individually controlled via a n × p matrix interconnection. In contrast to our earlier approach based on polyimide (PI) and epoxy resin with different thermal expansion coefficients, the μLEDs and interconnecting wires are now embedded into a triple-layer stack of a single, biocompatible, and highly transparent epoxy material...
2018: Frontiers in Neuroscience
Sun-Jie Xu, Qian Shen, Gui-E Chen, Zhen-Liang Xu
Organic solvent nanofiltration (OSN) membranes are always troubled by the "trade-off" effect between solvent flux and solute rejection. Hence, a rapid, convenient, and effective way to synthesize novel β-cyclodextrin-enhanced zeolite imidazole framework-8 (β-CD@ZIF-8) nanoparticles was first proposed and the nanoparticles were doped into both selective layer and poly( m -phenylene isophthalamide) support for fabricating thin-film nanocomposite membranes. Transmission/scanning electron microscopy images and X-ray photoelectron spectroscopy results demonstrate the successful synthesis of β-CD@ZIF-8...
September 30, 2018: ACS Omega
Bernardo Monteiro, Ana R Nabais, Maria H Casimiro, Ana P S Martins, Rute O Francisco, Luísa A Neves, Cláudia C L Pereira
The efficient separation of gases has industrial, economic, and environmental importance. Here, we report the improvement in gas separation performance of a polyimide-based matrix (Matrimid® 5218) filled with a Cu-based metal organic framework [MOF, Cu₃(BTC)₂] with two different ionic liquids (ILs) confined within the pores. The chosen ILs are commonly used in gas solubilization, 1-ethyl-3-methylimidazolium tetrafluoroborate ([EMIM][BF₄]) and 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][OTf]), and the incorporation of the [EMIM][BF₄]@Cu-BTC and [EMIM][OTf]@Cu-BTC composites in Matrimid® 5218 proved to be an efficient strategy to improve the permeability and selectivity toward CO₂/N₂ and CO₂/CH₄ mixtures...
October 11, 2018: Membranes
Ji Liu, Hao-Bin Zhang, Xi Xie, Rui Yang, Zhangshuo Liu, Yafeng Liu, Zhong-Zhen Yu
2D transition metal carbides and nitrides (MXenes) have gained extensive attention recently due to their versatile surface chemistry, layered structure, and intriguing properties. The assembly of MXene sheets into macroscopic architectures is an important approach to harness their extraordinary properties. However, it is difficult to construct a freestanding, mechanically flexible, and 3D framework of MXene sheets owing to their weak intersheet interactions. Herein, an interfacial enhancement strategy to construct multifunctional, superelastic, and lightweight 3D MXene architectures by bridging individual MXene sheets with polyimide macromolecules is developed...
October 7, 2018: Small
Daniel A Rau, Jana Herzberger, Timothy E Long, Christopher B Williams
All-aromatic polyimides have degradation temperatures above 500 °C, excellent mechanical strength, and chemical resistance, and are thus ideal polymers for high-temperature applications. However, their all-aromatic structure impedes additive manufacturing (AM) because of the lack of melt processability and insolubility in organic solvents. Recently, our group demonstrated the design of UV-curable polyamic acids (PAA), the precursor of polyimides, to enable their processing using vat photopolymerization AM...
October 8, 2018: ACS Applied Materials & Interfaces
Nate T Garland, Eric S McLamore, Nicholas D Cavallaro, Deyny Mendivelso-Perez, Emily A Smith, Dapeng Jing, Jonathan C Claussen
Flexible graphene electronics are rapidly gaining interest, but their widespread implementation has been impeded by challenges with ink preparation, ink printing, and post-print annealing processes. Laser-induced graphene (LIG) promises a facile alternative by creating flexible graphene electronics on polyimide substrates through a one-step laser writing fabrication method. Herein we demonstrate the use of LIG, created through a low-cost UV laser, for electrochemical ion selective sensing of plant-available nitrogen (i...
October 4, 2018: ACS Applied Materials & Interfaces
Ryan Cornelis Huiszoon, Sowmya Subramanian, Pradeep Ramiah Rajasekaran, Luke Beardslee, William Bentley, Reza Ghodssi
GOAL: This paper reports a platform for real-time monitoring and treatment of biofilm formation on 3D biomedical device surfaces. METHODS: We utilize a flexible platform consisting of gold interdigitated electrodes patterned on a polyimide substrate. The device was integrated onto the interior of a urinary catheter and characterization was performed in a custom-developed flow system. Biofilm growth was monitored via impedance change at 100 Hz AC with a 50 mV signal amplitude...
October 1, 2018: IEEE Transactions on Bio-medical Engineering
Ayelen Helling, Priyalakshmi Viswanathan, Katerina Cheliotis, Seyedeh Atefeh Mobasseri, Ying Yang, Alicia J El Haj, Fiona M Watt
The junction between the epidermal and dermal layers of human skin undulates, the width and depth of the undulations varying with age and disease. We previously showed that when primary human epidermal keratinocytes are seeded on collagen-coated undulating static polydimethylsiloxane (PDMS) elastomer substrates, the stem cells, differentiated cells and proliferating cells become patterned in response to cues from the underlying substrate. To investigate how patterning occurs over time, we have now created a dynamic model, in which a collagen-coated PLGA membrane is placed over a polyimide sheet containing circular holes, differing in diameter and spacing...
October 3, 2018: Tissue Engineering. Part A
Bendix Ketelsen, Mazlum Yesilmen, Hendrik Schlicke, Heshmat Noei, Chun-Hao Su, Ying-Chih Liao, Tobias Vossmeyer
In this study we developed a novel and efficient process for the fabrication of resistive strain gauges for healthcare related applications. First, 1,9-nonanedithiol (9DT) cross-linked gold nanoparticle (GNP) films were prepared via layer-by-layer (LbL) spin-coating and subsequently transferred onto flexible polyimide (PI) foil by contact printing. Four point bending tests revealed linear response characteristics with gauge factors of ~14 for 4 nm sized GNPs and ~26 for 7 nm sized GNPs. This dependency of strain sensitivity is attributed to the perturbation of charge carrier tunneling between neighboring GNPs, which becomes more efficient with increasing particle size...
October 3, 2018: ACS Applied Materials & Interfaces
L Qiu, Y Ouyang, Y Feng, X Zhang
Porous polyimide fiber enjoys a good reputation as a high temperature resistant thermal insulation material in an aircraft-carrier, a spacecraft, and other military sophisticated products. Understanding its thermal conductivity is especially important for the design optimization and thermal management in these applications. In this study, a modified wire-shape 3 ω method is developed to measure the thermal conductivity of individual porous polyimide fibers, utilizing a platinum layer heater/thermometer deposited along the circumferential direction of the fiber...
September 2018: Review of Scientific Instruments
Yang Liu, Gongping Liu, Chen Zhang, Wulin Qiu, Shouliang Yi, Valeriya Chernikova, Zhijie Chen, Youssef Belmabkhout, Osama Shekhah, Mohamed Eddaoudi, William Koros
Membrane-based separations offer great potential for more sustainable and economical natural gas upgrading. Systematic studies of CO2 /CH4 separation over a wide range of temperatures from 65 °C (338 K) to as low as -40 °C (233 K) reveals a favorable separation mechanism toward CO2 by incorporating Y- fum - fcu -MOF as a filler in a 6FDA-DAM polyimide membrane. Notably, the decrease of the temperature from 308 K down to 233 K affords an extremely high CO2 /CH4 selectivity (≈130) for the hybrid Y- fum - fcu -MOF/6FDA-DAM membrane, about four-fold enhancement, with an associated CO2 permeability above 1000 barrers...
September 2018: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Virginia Woods, Michael Trumpis, Brinnae Bent, Kay Palopoli-Trojani, Chia-Han Chiang, Charles Wang, Chunxiu Yu, Michele Insanally, Robert C Froemke, Jonathan Viventi
OBJECTIVE: The clinical use of microsignals recorded over broad cortical regions is largely limited by the chronic reliability of the implanted interfaces. APPROACH: We evaluated the chronic reliability of novel 61-channel micro-electrocorticographic (µECoG) arrays in rats chronically implanted for over one year and using accelerated aging. Devices were encapsulated with polyimide (PI) or liquid crystal polymer (LCP), and fabricated using commercial manufacturing processes...
September 24, 2018: Journal of Neural Engineering
Xiaohui Yan, Yingying Zhan, Dongdong Zhong, Yanshuo Li, Dapeng Wu
In order to achieve ultrafast solid phase micro-extraction (SPME) of trace organics in water samples, the robust polyimide/polyvinylpyrrolidone (PI/PVP) composite nanofiber was prepared by electrospinning. Unlike the nonwoven electrospun membrane bulk widely used for SPME, the hydrophilic PI/PVP nanofibers here can be easily dispersed into and recovered from water sample like a cloud, so nanofiber cloud SPME (NC-SPME) was proposed in this work. The extraction performance of the NC-SPME method was evaluated using phthalates and organochlorine pesticides as model analytes...
September 7, 2018: Journal of Chromatography. A
Pui-Kit Lee, Tian Tan, Shuo Wang, Wenpei Kang, Chun-Sing Lee, Denis Y W Yu
Silicon is an attractive high-capacity anode material for lithium-ion battery. With the help of nanostructures, cycling performance of silicon anode has improved significantly in the past couple of years. However, three major shortcomings associated with nanostructures still need to be addressed, namely, their high surface area, low tap density, and poor scalability. Herein, we present a facile and practical method to produce micron-sized Si secondary particle cluster (SiSPC) with a high tap density and a low surface area from bulk Si by high-energy ball-milling...
October 10, 2018: ACS Applied Materials & Interfaces
Yue Wang, Tian Yang, Yasushi Hasebe, Zhiqiang Zhang, Dongping Tao
Carbon black (CB) and carbon nanotube (CNT) co-doped polyimide (PI) modified glassy carbon electrode (CB-CNT/PI/GCE) was first prepared for the simultaneous determination of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The CB-CNT/PI/GCE exhibited persistent electrochemical behavior and excellent catalytic activities. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were used for the simultaneous detection of AA, DA, and UA in their ternary mixture. The peak separations between AA and DA, and DA and UA, are up to 166 mV and 148 mV, respectively...
September 12, 2018: Materials
Yuane Wu, Gong Chen, Chen Feng, Jiping Yang
To provide high-temperature polyimide matrix resins, novel carborane-containing thermosetting polyimides are presented. First, the low-viscosity carborane-containing imide oligomers are synthesized using newly designed 1-(3-amino-4-tolyl)-2-(4-aminophenyl)-o-carborane and aromatic dianhydride as monomers, 4-phenylethynyl phthalic anhydride as the end-capping reagent. Followed by thermal curing, the resulting polyimides show high Tg (≥500 °C) and above 92.1% char yield at 800 °C both in nitrogen and air atmosphere due to the incorporation of the bulky carborane cages...
September 10, 2018: Macromolecular Rapid Communications
Cyril Hnatovsky, Dan Grobnic, Stephen J Mihailov
Type II π-phase-shifted Bragg gratings stable up to ~1000°C are written inside a standard single mode silica optical fiber (SMF-28) with infrared femtosecond pulses and a special phase mask. Inscription through the protective polyimide fiber coating is also demonstrated. The birefringence of the Bragg gratings and, as a result, the polarization dependence of their spectra are strongly affected by the femtosecond laser polarization. Using optimized writing conditions, the full width at half maximum of the π-phase-shifted passband feature can be ~30 pm in transmission, while the polarization-dependent shift of its central wavelength can be less than 8 pm, for a 7 mm long grating structure...
September 3, 2018: Optics Express
Xinghua Zheng, Peng Yue, Shen Li, Liang Wang, Xiao Yang, Haisheng Chen
As one of the most basic properties of materials, thermal conductivity is a key parameter to investigate the analysis and design of the particular thermal process, such as the analysis of the thermal/cool energy storage and release process, the thermal/cool energy storage system design, and so on. Also, it is the foundation of energy technology development. In order to overcome the problem that the measurement frequency of a polyimide substrate independent detector is lower and the measurement time is longer, based on the relationship among 3ω detection frequency, thermal wave penetration depth, and thermal properties of the substrate material, this paper developed a stethoscope-type 3ω independent detector based on a sapphire substrate for fast measurement of material thermal conductivity...
August 2018: Review of Scientific Instruments
O F Manfredi, R S Mills, M M Schirru, R S Dwyer-Joyce
The ability to monitor the viscosity of lubricating oils within metallic products is of interest to many industries, these being the automotive, aerospace and food industries to name a few. Acoustic mismatch at the metallic-liquid interface restricts ultrasonic signal transmission and so limits applicability and sensitivity of the technique. In this work, we propose the use of a continuously repeated chirp (CRC) shear wave to amplify the measurable acoustic response to liquid viscosity. The technique enables multiple reflections to superimpose inside the component and form a quasi-static standing wave whose amplitude spectrum depends on the condition at the solid-liquid boundary...
August 7, 2018: Ultrasonics
Ming Chen, Zhenkai Li, Weimin Li, Chengwei Shan, Wenjie Li, Kaiwei Li, Guoqiang Gu, Ye Feng, Guohua Zhong, Lei Wei, Chunlei Yang
Advances in two-dimensional semiconducting thin films enable the realization of wearable electronic devices in the form factor of flexible substrate/thin films that can be seamlessly adapted in our daily lives. For wearable gas sensing, two-dimensional materials, such as SnSe2 , are particularly favorable because of their high surface-to-volume ratio and strong adsorption of gas molecules. Chemical vapor deposition and liquid/mechanical exfoliation are the widely applied techniques to obtain SnSe2 thin films...
November 9, 2018: Nanotechnology
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