Spiral Probe Research Articles

Polymer-based laminar probes with an ultra-long flexible spiral-shaped cable for in vivo neural recordings

Compared to conventional rigid silicon probes, flexible penetrating neural implants exhibit improved mechanical compliance with brain tissue, enabling high-quality neural recordings over extended periods of time. However, the length of the implantable shank and extension cable of most flexible devices falls short of clinical electrodes used in diagnostics and treatment of neurological disorders. In this study, we demonstrate the design, fabrication, and in vivo validation of polyimide-based neural probes with a thin spiral-shaped cable that reaches a length of 27 centimeters, comparable to that of clinical electrodes. The spiral probe comprises a 3.9-mm-long, 75–280-µm-wide and 10-µm-thick implantable shank with 24 linearly placed gold microelectrodes (diameter: 20 µm; electrode pitch: 150 µm) placed either close to the shank edge or centered on the shank. The electrical impedance of the microelectrodes was ∼266 kΩ at 1 kHz measured in vitro. In acute rodent experiments, we recorded high-quality local field potentials (e.g., cortical slow waves and hippocampal gamma activity), single and multiunit activities. In addition, the probes could simultaneously detect the activity of about 10 well-isolated single units, with an average spike amplitude of 65 µV. Furthermore, devices chronically implanted in rats successfully recorded spiking activity over several consecutive days. As demonstrated here, the developed spiral probes can be applied to various tasks, such as the laminar analysis of brain oscillations or the study of the sleep-wake cycle in naturally sleeping animals. In conclusion, our flexible probe design may stimulate the development of novel implantable devices for application in large animal models or clinical settings.

A simple and straightforward expression for curling probe electron density diagnosis in reactive plasmas

Active plasma resonance spectroscopy (APRS) refers to the family of plasma diagnostic methods which utilize the ability of plasmas to resonate at frequencies close to the plasma frequency. APRS operates by exciting the plasma with a weak RF signal by means of a small electric probe. The response of the plasma is recorded by a network analyzer (NA). A mathematical model is applied to derive characteristics like the electron density and the electron temperature. The curling probe is a promising realization of APRS. The curling probe is well-qualified for the local measurement of the electron density in reactive plasmas. This spiral probe resonates in plasma at a larger density dependent frequency than the plasma frequency. This manuscript represents a simple and straightforward expression relating this resonance frequency to the electron density of the plasma. A good agreement is observed between the proposed expression and the results obtained from previous studies and numerical simulations.

Design and evaluation of a high sensitivity spiral TDR scour sensor

Bridge scour accounts for more than half of the reported bridge failures in the United States. Scour monitoring technology based on time domain reflectometry (TDR) features the advantages of being automatic and inexpensive. The senior author’s team has developed a few generations of a TDR bridge scour monitoring system, which have succeeded in both laboratory and field evaluations. In this study, an innovative spiral TDR sensor is proposed to further improve the sensitivity of the TDR sensor in scour detection. The spiral TDR sensor is made of a parallel copper wire waveguide wrapped around a mounting rod. By using a spiral path for the waveguide, the TDR sensor achieves higher sensitivity than the traditional straight TDR probes due to longer travel distance of the electromagnetic (EM) wave per unit length in the spiral probe versus traditional probe. The performance of the new TDR spiral scour sensor is validated by calibration with liquids with known dielectric constant and wet soils. Laboratory simulated scour-refilling experiments are performed to evaluate the performance of the new spiral probe in detecting the sediment–water interface and therefore the scour-refill process. The tests results indicate that scour depth variation of less than 2 cm can be easily detected by this new spiral sensor. A theory is developed based on the dielectric mixing model to simplify the TDR signal analyses for scour depth detection. The sediment layer thickness (directly related to scour depth) varies linearly with the square root of the bulk dielectric constant of the water–sediment mixture measured by the spiral TDR probe, which matches the results of theoretical prediction. The estimated sediment layer thickness and therefore scour depth from the spiral TDR sensor agrees very well with that by direct physical measurement. The spiral TDR sensor is four times more sensitive than a traditional straight TDR probe.

Friction stir welding of PM2000 ODS alloy

Friction stir welding has been used to join sheets of a ferritic, oxide dispersion strengthened alloy, PM2000. A stepped spiral probe, polycrystalline cubic boron nitride tool, with a shoulder diameter of 25 mm, was used to weld 4 mm thick plate in a butt joint configuration. The thermomechanically affected zone underwent dynamic recrystallisation during welding; the resultant microstructure consisted of equiaxed ferritic grains containing a dispersion of yttrium aluminium oxides. Microindentation measurements revealed a significant reduction in hardness within the weld zone, when compared to the parent material. The welding process induced an overall coarsening of the yttrium aluminium oxide particles and depletion in their number density. However, the precipitation of secondary phase particles, likely to be oxides, which took place during the welding process, is indicative that an element of mechanical alloying occurs during the welding process. Annealing the welds for 1 h at 1380°C produced a massive recrystallised grain structure in the weld zone and a uniform hardness across the parent and weld was achieved. Transmission electron microscopy showed that, subsequent to annealing, particles were coarser in the weld zone (33 nm mean diameter) than in the parent alloy (24 nm mean diameter). However, electron diffraction and energy dispersive X-ray spectroscopy confirm that the dominant oxide phase, YAlO3 perovskite (YAP), was the same in both regions. Oxide particle size and number densities were not uniform throughout the weld. Focused ion beam prepared surfaces revealed particles within the size range of 50–600 nm diameter in material beneath the tool shoulder/workpiece contact area; the average size of dispersoids in this region was 130 nm.

Reversible Transverse Stress Effects on the Critical Current of an Internal Tin ${\rm Nb}_{3}{\rm Sn}$Strand Under Axial Strain

We have developed an apparatus to investigate the effect of transverse stress under axial strain on the critical current of superconducting strands. An internal tin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn wire is soldered on a C-shape ring (called Pacman) made of 2% beryllium doped copper alloy and axial strain from -0.7 to 0.7% can be applied. The actual strain on a sample was estimated from a comparison with the critical current measurement results using a Walter spiral probe. Reversible transverse stress effects on the critical current were studied in this work and the transverse pressure was applied up to 40 MPa under ±0.5% axial strain. The critical current was initially increased about 3% as transverse load was applied and then decreased almost linearly under compressive axial strain. Similar behavior is observed under tensile axial strain but the critical current decreases rather sharply at higher load. A unified description based on 3 dimensional deviatoric strain was difficult for the sample studied in this work.

Heat treatment effect on the strain dependence of the critical current for an internal-tin processed Nb 3Sn strand

A comparative study on the effects of heat treatment, especially, the duration of the A15 reaction temperature plateau on the strain dependence of the critical current for an internal-tin processed Nb 3Sn strand has been carried out. The strain dependence of the critical current is measured by a variable temperature Walter spiral probe that we have developed. It was shown that prolonged heat treatment can be a very effective way to improve the strain dependency. For a quantitative analysis, the measured data were analyzed with various proposed scaling laws: the scaling law based on strong-coupling theory, the modified deviatoric strain scaling law, and the interpolative scaling law. We found that there is a slight increase in the critical temperature and a substantial improvement in the maximum pinning force. The origin of improved strain dependency is further discussed.

Effect of tool geometry on tool wear characterization and weld formation in friction stir welding of 316L stainless steel

316L stainless steel plate was friction stir welded using PCBN tools. The effect of tool shoulder profile and tool probe profile on tool wear characterization and weld formation was investigated. Two different shoulder profiles (screw with different pitches) with four different tool probe profiles (two different probe end shapes and two different probe lengths) have been used to fabricate FSW zone. Experimental results show that the tools with narrow pitch screw shoulder profile produce deeper FSW zone compared to the tools with wide pitch. The tools with spiral probe profile produce deeper FSW zone compared to the tools with chamfer probe profile. The tools with wide pitch screw shoulder profile is apt to produce lower working loads. The wear resistant of tools with chamfer probe profile is significantly higher than that of tools with spiral probe profile. The relation between tool geometries and tool wear and weld formation is discussed.

A Variable Temperature Walters Spiral Probe for the Critical Current Measurement of Superconducting Strands

We have developed a probe for the critical current measurements of low temperature superconducting strands at various field, temperature and strain. A 30 cm-long strand sample is soldered on a Walters spiral made of beryllium copper alloy and compressive or tensile axial strain can be applied up to 0.7%. Temperature control ability was tested using a MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wire up to 30 K. Three cernox sensors are attached on a spiral adjacent to the strand and the temperature of the spiral is controlled within plusmn50 mK of target temperature during the critical current measurement up to 80 A. Extensive critical current measurements have been carried out for an internal-tin processed Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand. It was found that the measured field, temperature and strain dependence of the critical current for the internal-tin Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn strand is in agreement with the recent scaling law based on strong coupling theory of superconductivity.

Lacrimal canalicular repair. A simplified technique for intubation.

SUCCESS in treating the torn or obstructed lacrimal canaliculus rose markedly with Henderson's introduction of the temporarily-implanted polyethylene tube in 1950. 1,2 While most techniques for insertion have included opening the lacrimal sac surgically, 3-9 the latter aspect was made unnecessary for cases involving laceration or minor cicatrization (of short extent) by the advent of Worst's spiral probe. 10 Moreover, even this method can be made mechanically easier and shorter, eliminating the need for a prepositioned pancanalicular, intralumenal suture, by inserting the tubing along with the probe, as described below. Worst's spiral probe is a long-handled instrument to each end of which is attached a circularly-arranged or cork-screw-shaped lacrimal probe—the one turning clockwise and the other, counterclockwise (Fig 1). The technique to be described here consists of fenestrating the side of a length of polyethylene tubing of a carefully-selected caliber (thin-walled but semirigid, whose lumen will admit the spiral probe

Advisability of Substituting a Spiral Probe invented by the Author for Belloc's Instrument in Plugging the Back of the Nose

Advisability of Substituting a Spiral Probe invented by the Author for Belloc's Instrument in Plugging the Back of the Nose