Action potentials have a central role in the nervous system and in many cellular processes, notably those involving ion channels. The accurate measurement of action potentials requires efficient ...coupling between the cell membrane and the measuring electrodes. Intracellular recording methods such as patch clamping involve measuring the voltage or current across the cell membrane by accessing the cell interior with an electrode, allowing both the amplitude and shape of the action potentials to be recorded faithfully with high signal-to-noise ratios. However, the invasive nature of intracellular methods usually limits the recording time to a few hours, and their complexity makes it difficult to simultaneously record more than a few cells. Extracellular recording methods, such as multielectrode arrays and multitransistor arrays, are non-invasive and allow long-term and multiplexed measurements. However, extracellular recording sacrifices the one-to-one correspondence between the cells and electrodes, and also suffers from significantly reduced signal strength and quality. Extracellular techniques are not, therefore, able to record action potentials with the accuracy needed to explore the properties of ion channels. As a result, the pharmacological screening of ion-channel drugs is usually performed by low-throughput intracellular recording methods. The use of nanowire transistors, nanotube-coupled transistors and micro gold-spine and related electrodes can significantly improve the signal strength of recorded action potentials. Here, we show that vertical nanopillar electrodes can record both the extracellular and intracellular action potentials of cultured cardiomyocytes over a long period of time with excellent signal strength and quality. Moreover, it is possible to repeatedly switch between extracellular and intracellular recording by nanoscale electroporation and resealing processes. Furthermore, vertical nanopillar electrodes can detect subtle changes in action potentials induced by drugs that target ion channels.
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IJS, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Direct electrical recording and stimulation of neural activity using micro-fabricated silicon and metal micro-wire probes have contributed extensively to basic neuroscience and therapeutic ...applications; however, the dimensional and mechanical mismatch of these probes with the brain tissue limits their stability in chronic implants and decreases the neuron-device contact. Here, we demonstrate the realization of a three-dimensional macroporous nanoelectronic brain probe that combines ultra-flexibility and subcellular feature sizes to overcome these limitations. Built-in strains controlling the local geometry of the macroporous devices are designed to optimize the neuron/probe interface and to promote integration with the brain tissue while introducing minimal mechanical perturbation. The ultra-flexible probes were implanted frozen into rodent brains and used to record multiplexed local field potentials and single-unit action potentials from the somatosensory cortex. Significantly, histology analysis revealed filling-in of neural tissue through the macroporous network and attractive neuron-probe interactions, consistent with long-term biocompatibility of the device.
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IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SBMB, UL, UM, UPUK
Optical manipulation of biological cells and nanoparticles is significantly important in life sciences, early disease diagnosis, and nanomanufacturing. However, low-power and versatile all-optical ...manipulation has remained elusive. Herein, we have achieved light-directed versatile thermophoretic manipulation of biological cells at an optical power 100–1000 times lower than that of optical tweezers. By harnessing the permittivity gradient in the electric double layer of the charged surface of the cell membrane, we succeed at the low-power trapping of suspended biological cells within a light-controlled temperature gradient field. Furthermore, through dynamic control of optothermal potentials using a digital micromirror device, we have achieved arbitrary spatial arrangements of cells at a resolution of ∼100 nm and precise rotation of both single and assemblies of cells. Our thermophoretic tweezers will find applications in cellular biology, nanomedicine, and tissue engineering.
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IJS, KILJ, NUK, PNG, UL, UM
Steam generation, in terms of Marine boiler operation, involves a large number of potential failures and hazards, which impose high risks, causing deadly and costly accidents resulting in human ...casualties, machinery damage, ship operational disruption, and other financial losses. In this paper, in order to enhance the operational safety concepts onboard and for proactive contribution in the improvement of machinery system reliability, the potential failure modes are summarized by reviewing the past accident data and the reports, for the identification of the worst-case scenarios during boiler operations. For risk quantification and prioritization based on collected data from experts’ elicitations, a fuzzy set approach is developed using a Rule-based fuzzy logic system, modelled and tested using different types of membership functions for the calculation of the corresponding risk values, to assess their potential failure impacts. It is expected that the risk analysis method used in this study is applicable, and the results derived from this study can be used to help in the eradication of the potential failures, ultimately contributing to ship safety and system reliability.
•The main objectives were more education and better adaptation of safety assessments for the eradication of Marine accidents.•Integrated application of Marine boiler FMECA and Rule-based fuzzy logic method was carried out for risk prioritization.•Real-time accident-based FMECA Marine boiler study was carried out using Fuzzy expert system for better risk prioritization.•Quantitative risk assessment studies were performed for the 30 different FMs based on Marine Experts’ elicitations.•Based on the results obtained, the Fuel/Gas pipe leakage had the highest FRPN values.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Vertically aligned nanopillars can serve as excellent electrical, optical and mechanical platforms for biological studies. However, revealing the nature of the interface between the cell and the ...nanopillar is very challenging. In particular, a matter of debate is whether the cell membrane remains intact around the nanopillar. Here we present a detailed characterization of the cell-nanopillar interface by transmission electron microscopy. We examined cortical neurons growing on nanopillars with diameter 50–500 nm and heights 0.5–2 μm. We found that on nanopillars less than 300 nm in diameter, the cell membrane wraps around the entirety of the nanopillar without the nanopillar penetrating into the interior of the cell. On the other hand, the cell sits on top of arrays of larger, closely spaced nanopillars. We also observed that the membrane-surface gap of both cell bodies and neurites is smaller for nanopillars than for a flat substrate. These results support a tight interaction between the cell membrane and the nanopillars and previous findings of excellent sealing in electrophysiology recordings using nanopillar electrodes.
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IJS, KILJ, NUK, PNG, UL, UM
Directed migration of particles and molecules in a temperature gradient field, which is known as thermophoresis or the Soret effect, is of fundamental importance for mass transfer in colloid science ...and life sciences. However, thermophoretic tweezers that enable versatile particle manipulation have remained elusive due to the complex underlying physical forces in thermophoresis and the lack of general thermophilic particles above room temperature. Herein, we exploit entropic response and permittivity gradient at the particle-solvent interface to optically generated thermal gradient to achieve the thermophoretic trapping and dynamic manipulation of charged particles over an optothermal-responsive substrate. Engineering the interfacial properties, i.e., the surface charge of particles and the ionic strength of the solvent, further enhances the trapping efficiency. Through the rational design of optothermal potential profiles and substrate geometries, we have achieved various tweezing functionalities, including particle assembly, alignment, rotation and guiding, as well as precise transport of single nanoparticles. Based on the general concept of entropic change of polarized molecules structured at the particle-solvent interlayer, the thermophoretic tweezers are applicable to various types of particles, biological cells, and molecules and a wide range of solvents.
Cell migration in a cultured neuronal network presents an obstacle to selectively measuring the activity of the same neuron over a long period of time. Here we report the use of nanopillar arrays to ...pin the position of neurons in a noninvasive manner. Vertical nanopillars protruding from the surface serve as geometrically better focal adhesion points for cell attachment than a flat surface. The cell body mobility is significantly reduced from 57.8 μm on a flat surface to 3.9 μm on nanopillars over a 5 day period. Yet, neurons growing on nanopillar arrays show a growth pattern that does not differ in any significant way from that seen on a flat substrate. Notably, while the cell bodies of neurons are efficiently anchored by the nanopillars, the axons and dendrites are free to grow and elongate into the surrounding area to develop a neuronal network, which opens up opportunities for long-term study of the same neurons in connected networks.
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IJS, KILJ, NUK, PNG, UL, UM
Abstract
Ship–bank collisions linked to strong wind and ship–bank interaction pose a great threat to ships with large windage areas in restricted waters. In the analysis of ship–bank collision ...probability, maneuvering simulations with reasonable estimates of wind conditions and ship routes are important but have had little investigation. This paper presents a maneuverability-based analytical approach for evaluating the probability of a container ship colliding with a channel bank under strong wind. The Monte Carlo simulation technique is applied to conduct numerous runs of the maneuvering simulation. The steady state equations of ship motion and the time-domain simulation method are combined in this approach to detect a ship–bank collision. The input data for the simulation including wind speeds, wind directions, and ships' positions relative to the channel centerline are obtained from the meteorological data and the Automatic Identification System. The proposed approach is applied to a probabilistic analysis of a 10,000 TEU container ship entering Yangshan port, and discussion is given on the feasible ship speed and stacking configuration for reducing the probability of ship–bank collisions.
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