Assessment of whole blood coagulation with a microfluidic dielectric sensor.

Essentials ClotChip is a novel microsensor for comprehensive assessment of ex vivo hemostasis. Clinical samples show high sensitivity to detecting the entire hemostatic process. ClotChip readout exhibits distinct information on coagulation factor and platelet abnormalities. ClotChip has potential as a point-of-care platform for comprehensive hemostatic analysis. SUMMARY: Background Rapid point-of-care (POC) assessment of hemostasis is clinically important in patients with a variety of coagulation factor and platelet defects who have bleeding disorders. Objective To evaluate a novel dielectric microsensor, termed ClotChip, which is based on the electrical technique of dielectric spectroscopy for rapid, comprehensive assessment of whole blood coagulation. Methods The ClotChip is a three-dimensional, parallel-plate, capacitive sensor integrated into a single-use microfluidic channel with miniscule sample volume (< 10 µL). The ClotChip readout is defined as the temporal variation in the real part of dielectric permittivity of whole blood at 1 MHz. Results The ClotChip readout exhibits two distinct parameters, namely, the time to reach a permittivity peak (Tpeak ) and the maximum change in permittivity after the peak (Δεr,max ), which are, respectively, sensitive towards detecting non-cellular (i.e. coagulation factor) and cellular (i.e. platelet) abnormalities in the hemostatic process. We evaluated the performance of ClotChip using clinical blood samples from 15 healthy volunteers and 12 patients suffering from coagulation defects. The ClotChip Tpeak parameter exhibited superior sensitivity at distinguishing coagulation disorders as compared with conventional screening coagulation tests. Moreover, the ClotChip Δεr,max parameter detected platelet function inhibition induced by aspirin and exhibited strong positive correlation with light transmission aggregometry. Conclusions This study demonstrates that ClotChip assesses multiple aspects of the hemostatic process in whole blood on a single disposable cartridge, highlighting its potential as a POC platform for rapid, comprehensive hemostatic analysis.

Application of combined EBSD and 3D-SEM technique on crystallographic facet analysis of steel at low temperature.

Electron backscatter diffraction has been increasingly used to identify the crystallographic planes and orientation of cleavage facets with respect to the rolling direction in fracture surfaces. The crystallographic indices of cleavage planes can be determined either directly from the fracture surface or indirectly from metallographic sections perpendicular to the plane of the fracture surface. A combination of electron backscatter diffraction and 3D scanning electron microscopy imaging technique has been modified to determine crystallographic facet orientations. The main purpose of this work has been to identify the macroscopic crystallographic orientations of cleavage facets in the fracture surfaces of weld heat affected zones in a well-known steel fractured at low temperatures. The material used for the work was an American Petroleum Institute (API) X80 grade steel developed for applications at low temperatures, and typical heat affected zone microstructures were obtained by carrying out weld thermal simulation. The fracture toughness was measured at different temperatures (0°C, -30°C, -60°C and -90°C) by using Crack Tip Opening Displacement testing. Fracture surfaces and changes in microstructure were analyzed by scanning electron microscopy and light microscopy. Crystallographic orientations were identified by electron backscatter diffraction, indirectly from a polished section perpendicular to the major fracture surface of the samples. Computer assisted 3D imaging was used to measure the angles between the cleavage facets and the adjacent polished surface, and then these angles were combined with electron backscatter diffraction measurements to determine the macroscopic crystallographic planes of the facets. The crystallographic indices of the macroscopic cleavage facet planes were identified to be {100}, {110}, {211} and {310} at all temperatures.

Anomalous modulation of a zero-bias peak in a hybrid nanowire-superconductor device.

We report on transport measurements of an InAs nanowire coupled to niobium nitride leads at high magnetic fields. We observe a zero-bias anomaly (ZBA) in the differential conductance of the nanowire for certain ranges of magnetic field and chemical potential. The ZBA can oscillate in width with either the magnetic field or chemical potential; it can even split and re-form. We discuss how our results relate to recent predictions of hybridizing Majorana fermions in semiconducting nanowires, while considering more mundane explanations.

A Wireless IC for Wide-Range Neurochemical Monitoring Using Amperometry and Fast-Scan Cyclic Voltammetry.

An integrated circuit for real-time wireless monitoring of neurochemical activity in the nervous system is described. The chip is capable of conducting measurements in both fast-scan cyclic voltammetry (FSCV) and amperometry modes for a wide input current range. The chip architecture employs a second-order DeltaSigma modulator (DeltaSigmaM) and a frequency-shift-keyed transmitter operating near 433 MHz. It is fabricated using the AMI 0.5-mum double-poly triple-metal n-well CMOS process, and requires only one off-chip component for operation. A measured current resolution of 12 pA at a sampling rate of 100 Hz and 132 pA at a sampling rate of 10 kHz is achieved in amperometry and 300-V/s FSCV modes, respectively, for any input current in the range of plusmn430 nA. The modulator core and the transmitter draw 22 and 400 muA from a 2.6-V power supply, respectively. The chip has been externally interfaced with a carbon-fiber microelectrode implanted acutely in the caudate-putamen of an anesthetized rat, and, for the first time, extracellular levels of dopamine elicited by electrical stimulation of the medial forebrain bundle have been successfully recorded wirelessly using 300-V/s FSCV.

Wireless multichannel biopotential recording using an integrated FM telemetry circuit.

This paper reports on the design, implementation, and testing of wireless multichannel recording microsystems featuring on-chip AC amplification, DC input stabilization, time-division-multiplexing, and wireless FM reconstruction of input biopotentials with frequency contents from 0.05-6 kHz with measured I/O correlation coefficients in the range of 70-94% per channel for spike train input amplitudes of 0.2-2 mV(p-p) while dissipating only 2.2 mW from 3 V. The 4.84 mm(2) IC is fabricated using AMI 1.5 microm 2P2M CMOS process, and is successfully interfaced with a micromachined silicon probe for simultaneous multichannel wireless in vitro recording of simulated neural spikes at 98 MHz with measured I/O correlation coefficients of >80%.

An ultralight biotelemetry backpack for recording EMG signals in moths.

A two-channel FM biopotential recording system fabricated on a foldable, lightweight, polyimide substrate is presented. Each channel consists of a biopotential amplifier followed by a Colpitts oscillator with operating frequency tunable in the 88-108 MHz commercial FM band. The overall system measures 10 mm X 10 mm X 3 mm, weighs 0.74 g, uses two 1.5-V batteries, dissipates about 2 mW, and has a transmission range of 2 m. Using this system, electromyogram signals have been recorded from the dorsal ventral muscle and the dorsal longitudinal muscle of a giant sphinx moth (manduca sexta).