Metal ions responsive nanochannel by H2S absorbed in Metal-Organic Framework-based micropipette

Glass micropipette has characteristics of easy fabrication, excellent flexibility and stable properties. The HKUST-1 and MIL-68(In) in-situ grow into the tip of micropipette to construct the porous nanochannel. After absorbing...

Detachable glass microelectrodes for recording action potentials in active moving organs

Here, we describe new detachable floating glass micropipette electrode devices that provide targeted action potential recordings in active moving organs without requiring constant mechanical constraint or pharmacological inhibition of tissue motion. The technology is based on the concept of a glass micropipette electrode that is held firmly during cell targeting and intracellular insertion, after which a 100-µg glass microelectrode, a “microdevice,” is gently released to remain within the moving organ. The microdevices provide long-term recordings of action potentials, even during millimeter-scale movement of tissue in which the device is embedded. We demonstrate two different glass micropipette electrode holding and detachment designs appropriate for the heart (sharp glass microdevices for cardiac myocytes in rats, guinea pigs, and humans) and the brain (patch glass microdevices for neurons in rats). We explain how microdevices enable measurements of multiple cells within a moving organ that are typically difficult with other technologies. Using sharp microdevices, action potential duration was monitored continuously for 15 min in unconstrained perfused hearts during global ischemia-reperfusion, providing beat-to-beat measurements of changes in action potential duration. Action potentials from neurons in the hippocampus of anesthetized rats were measured with patch microdevices, which provided stable base potentials during long-term recordings. Our results demonstrate that detachable microdevices are an elegant and robust tool to record electrical activity with high temporal resolution and cellular level localization without disturbing the physiological working conditions of the organ. NEW & NOTEWORTHY Cellular action potential measurements within tissue using glass micropipette electrodes usually require tissue immobilization, potentially influencing the physiological relevance of the measurement. Here, we addressed this limitation with novel 100-µg detachable glass microelectrodes that can be precisely positioned to provide long-term measurements of action potential duration during unconstrained tissue movement.

The glass micropipette electrode: A history of its inventors and users to 1950

Soon after the glass micropipette was invented as a micro-tool for manipulation of single bacteria and the microinjection and microsurgery of living cells, it was seen to hold promise as a microelectrode to stimulate individual cells electrically and to study electrical potentials in them. Initial successes and accurate mechanistic explanations of the results were achieved in giant plant cells in the 1920s. Long known surface electrical activity in nerves and muscles was only resolved at a similar cellular level in the 1930s and 1940s after the discovery of giant nerve fibers and the development of finer tipped microelectrodes for normal-sized cells.

Circuit Models and Experimental Noise Measurements of Micropipette Amplifiers for Extracellular Neural Recordings from Live Animals

Glass micropipettes are widely used to record neural activity from single neurons or clusters of neurons extracellularly in live animals. However, to date, there has been no comprehensive study of noise in extracellular recordings with glass micropipettes. The purpose of this work was to assess various noise sources that affect extracellular recordings and to create model systems in which novel micropipette neural amplifier designs can be tested. An equivalent circuit of the glass micropipette and the noise model of this circuit, which accurately describe the various noise sources involved in extracellular recordings, have been developed. Measurement schemes using dead brain tissue as well as extracellular recordings from neurons in the inferior colliculus, an auditory brain nucleus of an anesthetized gerbil, were used to characterize noise performance and amplification efficacy of the proposed micropipette neural amplifier. According to our model, the major noise sources which influence the signal to noise ratio are the intrinsic noise of the neural amplifier and the thermal noise from distributed pipette resistance. These two types of noise were calculated and measured and were shown to be the dominating sources of background noise forin vivoexperiments.

Handling technology for 0.075-square mm powder IC chip

We have developed a packaging technology for powder IC chip of 0.075-square mm × 5 μm thickness. The chip, which can be embedded into papers, is expected to be a key device in pioneering new markets, where it can cheaply and easily manage a number of articles and identify papers such as securities. Manipulating a fine chip in a dry environment has been difficult due to adhesion of the other chips and scattering from the influence of electrostatic phenomena. However, using the micro-bead and cell trapping technology, it is possible to put the chips on a substrate one by one. The technique uses a double-surface-electrode chip, and a novel water-based chip handling technique composed of a micropipette manipulation and a self-aligned positioning. The double-surface-electrode structure that has two individual surface electrodes is advantageous in that when mounting the powder chip on a substrate, the chips are placed on the substrate without the need for highly accurate positioning, including the chip orientation control (upside-down, rotation). As for the micropipette manipulation, the chips are kept dispersed by stirring liquid with addition of a 0.5% surfactant to prevent chips from sticking together, and a flat-end glass micropipette successfully manipulated a single chip with high chip-capturing ratio. The self-aligned positioning of the chip uses micro liquid droplet shrinkage during evaporation process. The chip was able to move together with the droplet edge, and was positioned in the predefined hydrophilic domain. The liquid cushioning pick-up and placing action enables stress-free handling.