A flexible electrode array for determining regions of motor function activated by epidural spinal cord stimulation in rats with spinal cord injury

Epidural stimulation of the spinal cord is a promising technique for the recovery of motor function after spinal cord injury.The key challenges within the reconstruction of motor function for paralyzed limbs are the precise control of sites and parameters of stimulation.To activate lower-limb muscles precisely by epidural spinal cord stimulation,we proposed a high-density,flexible electrode array.We determined the regions of motor function that were activated upon epidural stimulation of the spinal cord in a rat model with complete spinal cord,which was established by a transection method.For evaluating the effect of stimulation,the evoked potentials were recorded from bilateral lowerlimb muscles,including the vastus lateralis,semitendinosus,tibialis anterior,and medial gastrocnemius.To determine the appropriate stimulation sites and parameters of the lower muscles,the stimulation characteristics were studied within the regions in which motor function was activated upon spinal cord stimulation.In the vastus lateralis and medial gastrocnemius,these regions were symmetrically located at the lateral site of L1 and the medial site of L2 vertebrae segment,respectively.The tibialis anterior and semitendinosus only responded to stimulation simultaneously with other muscles.The minimum and maximum stimulation threshold currents of the vastus lateralis were higher than those of the medial gastrocnemius.Our results demonstrate the ability to identify specific stimulation sites of lower muscles using a high-density and flexible array.They also provide a reference for selecting the appropriate conditions for implantable stimulation for animal models of spinal cord injury.This study was approved by the Animal Research Committee of Southeast University,China(approval No.20190720001) on July 20,2019.

Preparation of Electrode Array by Electrochemical Etching Based on FEM

Process technology of multiple cylindrical micro-pins by wire-electrical discharge machining （wire-EDM） and electrochemical etching was presented. A row of rectangular micro-columns were machined by wire-EDM and then machined into cylindrical shape by electrochemical etching. However, the shape of the multiple electrodes and the consistent sizes of the electrodes row are not easy to be controlled. In the electrochemical process, the shape of the cathode electrode determines the current density distribution on the anode and so the forming of multiple electrodes. This paper proposes a finite element method （FEM） to accurately optimize the electrode profile. The microelectrodes row with uniformity diameters with size from hundreds micrometers to several decades could be fabricated, and mathematical model controlling the shape and diameter of multiple microelectrodes was provided. Furthermore, a good agreement between experimental and theoretical results was confirmed.

Ion Selective Electrode Array Analysis Using Variable Step-Size Generalized Simulated Annealing

A global optimum location algorithm called Variable Step-Size Generalized Simulated Annealing(VSGSA) was applied to treating the data obtained by using an array of ion-electrodes in solutions containing mixtures of Na+, K+, Ca2+. Unlike traditional optimization algorithms such as simplex procedure, VSGSA can be used to determine the model parameters without any priori information about the analytical system under investigation and overcome the disadvantage of simplex method which might converge to local extrema depending on the starting positions. The algorithm was applied to po-tentiometric determination of ions in mixture solutions.

Research software in cochlear duct length estimation,Greenwood frequency mapping and CI electrode array length simulation

Background and objective:The size of the cochlea varies a lot among the human population bringing the necessity for electrode arrays to be available in various lengths irrespective of the cochlear implant(CI)brand.This research software helps in the estimation of the patient’s cochlear duct length(CDL)which is then used for the simulation of the correct length electrode array matching the patient’s cochlear size and as well in getting the patient specific cochlear frequency map.Methods:Visual Studio Express 2012 for Windows Desktop is used in the architecture of this research software.The basal turn diameter of the cochlea("A"value)needs to be measured from the pre-operative computed tomography(CT)image of the patient’s temporal bone.This"A"will be taken as the input for the CDL equations proposed by Alexiades et al for estimating the CDL along the basilar membrane for various insertion depths.Greenwood’s equation is then used in combination with the CDL for the full length of the cochlea in getting the patient specific frequency map.Results:The research software with the help of the"A"value as input,with few button clicks,gives the patient specific CDL for various insertion depths and the Greenwood’s frequency map.The users have the choice to select any electrode array of their choice and place it under the frequency map to see how good it fits to that particular patient’s cochlea.Also,given the possibility to drag and move the electrode array picture to mimic the post-operative actual electrode insertion depth.Conclusions:This research software simplifies the overall process of CDL estimation and in getting the patient specific cochlear frequency map.The clinicians get the chance to simulate placing the various electrode array lengths in patient cochlea in identifying the best fit electrode.This could help in pushing the CI field into the concept of individualized CI electrode array solution that ultimately benefits the patients.

Cutaneous sensory nerve as a substitute for auditory nerve in solving deaf-mutes' hearing problem: an innovation in multi-channel-array skin-hearing technology

The current use of hearing aids and artificial cochleas for deaf-mute individuals depends on their auditory nerve. Skin-hearing technology, a patented system developed by our group, uses a cutaneous sensory nerve to substitute for the auditory nerve to help deaf-mutes to hear sound. This paper introduces a new solution, multi-channel-array skin-hearing technology, to solve the problem of speech discrimination. Based on the filtering principle of hair cells, external voice sig- nals at different frequencies are converted to current signals at corresponding frequencies using electronic multi-channel bandpass filtering technology. Different positions on the skin can be stimulated by the electrode array, allowing the perception and discrimination of external speech signals to be determined by the skin response to the current signals. Through voice frequen- cy analysis, the frequency range of the band-pass filter can also be determined. These findings demonstrate that the sensory nerves in the skin can help to transfer the voice signal and to dis- tinguish the speech signal, suggesting that the skin sensory nerves are good candidates for the replacement of the auditory nerve in addressing deaf-mutes＇ hearing problems. Scientific hearing experiments can be more safely performed on the skin. Compared with the artificial cochlea, multi-channel-array skin-hearing aids have lower operation risk in use, are cheaper and are more easily popularized.

Erosion-corrosion and its mitigation on the internal surface of the expansion segment of N80 steel tube

We investigated erosion-corrosion(E-C) and its mitigation on the internal surface of the expansion segment of N80 steel tube in a loop system using array electrode technique, weight-loss measurement, computational-fluid-dynamics simulation, and surface characterization techniques.The results show that high E-C rates can occur at locations where there is a high flow velocity and/or a strong impact from sand particles, which results in different E-C rates at various locations.Consequently, it can be expected that localized corrosion often occurs in such segments.The E-C rate at each location in the expansion segment can be significantly mitigated with an imidazoline derivative inhibitor, as the resulting inhibitor layer significantly impedes the electrochemical reaction rate.However, we found that this inhibitor layer could not effectively reduce the difference in the erosion rates at different locations on the internal surface of the expansion segment.This means that localized corrosion can still occur at the expansion segment despite the presence of the inhibitor.

Electronic Excitation Temperature in DC Positive Streamer Discharge

The electronic excitation temperature in a direct current positive streamer discharge based on ultra-thin sheet electrodes was measured by optical emission spectrometry in order to deposit materials for potential future applications. It was remarkable that the electronic excitation temperature （Text） did not vary monotonically with the discharge current, but demonstrated a peak at a certain position. In a mixture of oxygen and argon （80% oxygen）, the maximum Texc reached about 6300 K at an average current of 600 pA. Both the positive ions accumulation in the discharge region and the increase of the local temperature around the streamer channel caused by Joule heating are considered to be the main reasons for the variations of Texc.

High-resolution and large-size stretchable electrodes based on patterned silver nanowires composites

Electrodes based on composites of silver nanowires(AgNWs)and elastic polymers have been widely studied and applied in various stretchable electronic devices.However,due to the high aspect ratio of nanowires,the patterning of AgNW-based composite electrodes remains a huge challenge,especially for high-resolution complex circuit wiring on large-size elastic substrates.In this paper,we propose a method for preparing large-size stretchable circuit boards with high-resolution electrodes by the combination of screen printing and vacuum filtration of AgNWs/polydimethylsiloxane(PDMS)composite.The as-prepared stretchable electrodes have smooth edges with patterning resolution up to-50 μm.The conductivity of the composite electrode can be precisely controlled by varying deposition densities of AgNWs and have reached to 1.07 x 10^(4) S/cm when the deposition density was 2.0 mg/cm^(2).In addition,the uniformity of conductivity and the resistance-strain characteristics of composite electrodes were systematically evaluated with different AgNWs deposition densities.The composite electrodes have been successfully employed to construct a large-size programmable display system and an 18-channel surface electromyography(EMG)recording,showing great potentials for some strain-insensitive stretchable circuits in wearable and health-related electronic applications.

Engineering the grain boundary:a promising strategy to configure NiCoP_(4)O_(12)/NiCoP nanowire arrays for ultra-stable supercapacitor

NiCoP_(4)O_(12)/NiCoP nanorod-like arrays with tunable grain boundary density and pores were synthesized by the processes composed of hydrothermal and pyrolysis,in which,the electron structure of Ni and Co atoms characterized by X-ray photoelectron spectroscopy was contemporaneous inverse manipulated.The optimized NiCoP_(4)O_(12)/NiCoP arrays have a high specific capacitance of 507.8μAh∙cm^(–2)at 1 mA∙cm^(–2),and good rate ability of 64.7%retention at 30-folds increased current density.Importantly,an ultra-stable ability,88.5%of retention after 10000 cycles,was achieved in an asymmetric cell assembled of the NiCoP_(4)O_(12)/NiCoP arrays with activated carbon.In addition,the energy and power densities of an asymmetric cell were higher than those of other work,demonstrating as-prepared NiCoP_(4)O_(12)/NiCoP arrays are promising electrodes for supercapacitors.

Combined experimental and simulation study on corrosion behavior of B10 copper-nickel alloy welded joint under local turbulence

The corrosion behavior of B10 copper-nickel alloy welded joints in seawater pipeline system was analyzed under local turbulence induced by weld residual height.The corrosion behavior was evaluated by array electrode technology,mor-phology and elemental characterization,and COMSOL Multiphysics simulation.The results provide a theoretical basis for the corrosion and leakage of B10 alloy in seawater pipeline under the action of turbulence.The results show that residual height-induced turbulence exhibits a significant effect on the corrosion behavior in different areas of welded joints in B10 alloy.Turbulence can damage some surfaces,causing polarity deflection followed by acceleration of corrosion,or it is easier to form a protective film to slow down corrosion.COMSOL Multiphysics results show that the shear rate and turbulent kinetic energy increase linearly with the increase in residual height and velocity.The corrosion behavior of alloy surface is influenced by controlling the mass transfer rate and surface state.

Clinical and scientific innovations in auditory brainstem implants

The auditory brainstem implant(ABI)was originally developed to provide rehabilitation of retrocochlear deafness caused by neurofibromatosis type 2(NF2).Recent studies of the ABI have investigated outcomes in non-NF2 cohorts,such as patients with cochlear nerve aplasia or cochlear ossification and more recently,intractable tinnitus.New technologies that improve the ABI-neural tissue interface are being explored as means to improve performance and decrease side effects.Innovative discoveries in optogenetics and bioengineering present opportunities to continually evolve this technology into the future,enhancing spatial selectivity of neuronal activation in the cochlear nucleus and preventing side effects through reduction in activation of non-target neuronal circuitry.These advances will improve surgical planning and ultimately improve patients1 audiological capabilities.ABI research has rapidly increased in the 21st century and applications of this technology are likely to continually evolve.Herein,we aim to characterize ongoing clinical,basic science,and bioengineering advances in ABIs and discuss future directions of this technology.

Automatic decomposition of pediatric high density surface EMG:A pilot study

This pilot study presents a novel application of high density surface electromyography(EMG)decomposition in pediatric patients,with a view toward promoting its potential clinical application for examination of pediatricneuromuscular diseases.Automatic progressive FastICA peel-off(APFP)framework was used to decompose high density surface EMG signals recorded from the first dorsal interosseous and abductor pollicis brevis muscles ofchildren with spinal muscular atrophy.The performance of the decomposition with reduced EMG recordingchannels was also investigated.In total 131 motor units were extracted from 15 trials of 64-channel(8×8)surface EMG.The decomposition yield reduced to 102 motor units when 36-channel(6×6)was used,amongwhich 84 motor units were common ones with an average matching rate of(95.68±5.26)%.The decompositionyield further reduced to 65 motor units when only 16-channel(4×4)was used,among which 57 were common ones with an average matching rate of(95.99±4.56)%.These results indicate that using the APFP frameworksingle motor unit activity can be reliably and automatically extracted from pediatric surface EMG signals recordedby an electrode array,which can facilitate potential clinical application of surface EMG as an alternative or supplement to invasive needle EMG for examination of neuromuscular diseases in children.