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Polymer-fiber-coupled field-effect sensors for label-free deep brain recordings
摘要： Electrical recording permits direct readout of neural activity but offers limited ability to correlate it to the network topography. On the other hand, optical imaging reveals the architecture of neural circuits, but relies on bulky optics and fluorescent reporters whose signals are attenuated by the brain tissue. Here we introduce implantable devices to record brain activities based on the field effect, which can be further extended with capability of label-free electrophysiological mapping. Such devices reply on light-addressable potentiometric sensors (LAPS) coupled to polymer fibers with integrated electrodes and optical waveguide bundles. The LAPS utilizes the field effect to convert electrophysiological activity into regional carrier redistribution, and the neural activity is read out in a spatially resolved manner as a photocurrent induced by a modulated light beam. Spatially resolved photocurrent recordings were achieved by illuminating different pixels within the fiber bundles. These devices were applied to record local field potentials in the mouse hippocampus. In conjunction with the raster-scanning via the single modulated beam, this technology may enable fast label-free imaging of neural activity in deep brain regions.
关键词： light-addressable potentiometric sensors,polymer fibers,deep brain recordings,label-free,field-effect
更新于2025-09-16 10:30:52
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Surface regeneration and reusability of label-free DNA biosensors based on weak polyelectrolyte-modified capacitive field-effect structures
摘要： The reusability of capacitive field-effect electrolyte-insulator-semiconductor (EIS) sensors modified with a cationic weak polyelectrolyte (poly(allylamine hydrochloride) (PAH)) for the label-free electrical detection of single-stranded DNA (ssDNA), in-solution- and on-chip-hybridized double-stranded DNA (dsDNA) has been studied. It has been demonstrated that via simply regeneration of the gate surface of the EIS sensor by means of an electrostatic adsorption of a new PAH layer, the same biosensor can be reused for at least five DNA-detection measurements. Because of the reversal of the charge sign of the outermost layer after each surface modification with the cationic PAH or negatively charged DNA molecules, the EIS-biosensor signal exhibits a zigzag-like behavior. The amplitude of the signal changes has a tendency to decrease with increasing number of macromolecular layers. The direction of the EIS-signal shifts can serve as an indicator for a successful DNA-immobilization or -hybridization process. In addition, we observed that the EIS-signal changes induced by each surface-modification step (PAH adsorption, immobilization of ssDNA or dsDNA molecules and on-chip hybridization of complementary target cDNA) is decreased with increasing the ionic strength of the measurement solution, due to the more efficient macromolecular charge-screening by counter ions. The results of field-effect experiments were supported by fluorescence-intensity measurements of the PAH- or DNA-modified EIS surface using various fluorescence dyes.
关键词： charge screening,label-free,field-effect sensor,DNA biosensor,reusability,weak polyelectrolyte
更新于2025-09-09 09:28:46
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[IEEE 2018 34th International Conference on Lightning Protection (ICLP) - Rzeszow (2018.9.2-2018.9.7)] 2018 34th International Conference on Lightning Protection (ICLP) - On In Situ Lightning Current Impulse Testing in a Large Free Field PV Plant
摘要： Lightning ground potential rise (GPR) was shown to be a significant contributor to equipment damage under certain conditions that include, in particular, high soil resistivity. In addition, IEEE Std 1692 suggested that surge protective devices (SPDs) may not protect adequately under conditions of lightning GPR. This paper follows on earlier work that addressed lightning GPR associated with large electrodes, loss of equipotential under conditions of GPR and a desk-top study on the behavior of a low voltage SPD under emulated lightning impulse conditions. The findings of a laboratory test on the behavior of an SPD under lightning current impulse conditions as well as in situ testing of an SPD under lightning current impulse are presented in this paper. The paper concludes by reflecting on initial findings from post-test monitoring under actual lightning, emphasizes the value of in situ testing and points out its limitations.
关键词： current,lightning,free field,in situ,plant,test,photovoltaic,impulse
更新于2025-09-09 09:28:46