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In This Article

  • Summary
  • Abstract
  • Introduction
  • Protocol
  • Representative Results
  • Discussion
  • Acknowledgements
  • Materials
  • References
  • Reprints and Permissions

Summary

Our purpose was to provide an updated, easy-to-follow guide on the fabrication and testing of epimysial electromyography electrodes. To that end, we provide instructions for material sourcing and a detailed walkthrough of the fabrication and testing process.

Abstract

Electromyography (EMG) is a valuable diagnostic tool for detecting neuromuscular abnormalities. Implantable epimysial electrodes are commonly used to measure EMG signals in preclinical models. Although classical resources exist describing the principles of epimysial electrode fabrication, there is a sparsity of illustrative information translating electrode theory to practice. To remedy this, we provide an updated, easy-to-follow guide on fabricating and testing a low-cost epimysial electrode.

Electrodes were made by folding and inserting two platinum-iridium foils into a precut silicone base to form the contact surfaces. Next, coated stainless steel wires were welded to each contact surface to form the electrode leads. Lastly, a silicone mixture was used to seal the electrode. Ex vivo testing was conducted to compare our custom-fabricated electrode to an industry standard electrode in a saline bath, where high levels of signal agreement (sine [intraclass correlation - ICC= 0.993], square [ICC = 0.995], triangle [ICC = 0.958]), and temporal-synchrony (sine [r = 0.987], square [r = 0.990], triangle [r= 0.931]) were found across all waveforms. Low levels of electrode impedance were also quantified via electrochemical impedance spectroscopy.

An in vivo performance assessment was also conducted where the vastus lateralis muscle of a rat was surgically instrumented with the custom-fabricated electrode and signaling was acquired during uphill and downhill walking. As expected, peak EMG activity was significantly lower during downhill walking (0.008 ± 0.005 mV) than uphill (0.031 ± 0.180 mV, p = 0.005), supporting the validity of the device. The reliability and biocompatibility of the device were also supported by consistent signaling during level walking at 14 days and 56 days post implantation (0.01 ± 0.007 mV, 0.012 ± 0.007 mV respectively; p > 0.05) and the absence of histological inflammation. Collectively, we provide an updated workflow for the fabrication and testing of low-cost epimysial electrodes.

Introduction

Electromyography (EMG) is a powerful tool for studying the electrical activity of muscle. EMG recordings can be especially useful in preclinical animal models to assess the effectiveness of interventions to treat neuromuscular dysfunction. In these models, implantable biocompatible electrodes are commonly used to assess the neurophysiological interface between motor neurons and muscle fibers. These implantable electrodes can provide localized measurements of muscle excitation and can be diverse in terms of their configuration, shape, and material, with the optimal design ultimately dictated by the location and intended use.

Despite their su....

Protocol

The in vivo procedure was conducted under the approval of the Institutional Animal Care & Use Committee at the University of Michigan (IACUC approval #PRO00010765) and in accordance with the National Institutes of Health guidelines on the care and use of laboratory animals.

1. Electrode sourcing and fabrication

NOTE: Figure 1 provides a high-level summary of all key fabrication steps with a QR link that provides addit.......

Representative Results

Ex vivo performance
ICCs revealed high levels of agreement between the custom-fabricated and industry standard electrodes across all waveforms (sine [ICC = 0.993], square [ICC = 0.995], triangle [ICC = 0.958]; p < .001). Bland-Altman plots also revealed a high degree of signal agreement between electrodes. Bland Altman plots and Pearson correlations are summarized in Figure 3 with strong positive correlations between the custom-fabricated and industry stan.......

Discussion

Our objective was to streamline the EMG fabrication process, enabling broader adoption and implementation of epimysial electrode designs, thus promoting accessibility, and advancing neuromuscular research. To this end, we present a user-friendly guide for sourcing, fabricating, and testing low-cost epimysial electrodes in-house. In hopes of supporting other research groups, we also provide supplemental 3D printing templates to facilitate the production of in-house epimysial electrodes for their research endeavors.

Acknowledgements

This work was supported by the National Institute of Arthritis and Musculoskeletal and Skin Diseases Grant R01AR081235 (to L. K. Lepley). The authors thank the following individuals for their contribution to the fabrication and testing of our biocompatible electrode: Joel Pingel, Grant Gueller, Akhil Ramesh, Joe Letner, Jacky Tian, and Ross Brancati.

....

Materials

NameCompanyCatalog NumberComments
Electrode Materials
         Quantity & price per electrode
Contact surfacePrince and Izant PT90/IR10 1.25 mm x 5 mm foilCatalog #1040055 2 per electrode
$7.50 per foil
$15.00 per electrode
PFA coated stainless-steel electrode lead wire A-M Systems Multi-Stranded PFA-Coated Stainless Steel Wire 50.8 µm strand diameter Catalog #793500Dependent on desired lead length (e.g., 9 inch lead wires x2)
$128 per 25 ft spool
$5.12 per foot
$0.42 per inch (x18)
$7.68 per electrode
Folding jig 3D printed
(see .gcode file)
NANA
Sealant for electrode bodyNusil Med-1137 liquid siliconeCatalog #MED-11371 gram
$344.66 per 2 oz. (59.15 mL)
$5.83 per electrode
Silicone baseImplantech Alliedsil Silicone Sheeting-Reinforced, Long Term Implantable (8” x 6”) .007 thickCatalog #701-07 10mm x 5mm sheet
$225.00 per 8 x 6 inch
$0.36 per electrode (10 mm x 5 mm)
 Thinner for sealant mixtureToluene 99.5% ACS Reagent 500mL or Xylene ACS 99.5%Catalog #179418-500 ML0.75 mL
$25.53 per 500 mL
$0.38 per electrode
Template for perforating silicone baseCutting jig – 3D printed
(see CAD file)
NANA
Custom-fabricated electrode: $29.25
Industry standard electrode (EP105 EMG Patch Electrode, 2 contacts, single-sided, 7mm x 4mm, MicroProbe for Life Science): $305.00
Additional Fabrication Materials 
            Quantity & price per electrode
3D printing software Solidworks (Solidworks, 2022)
Micro-Tig welder Micro-Tig Welder (CD1000SPM, Single Pulse Research and Light Production Resistance Spot Welder, Sunstone)SKU 301010$3,500
Ultrasonic bathUltrasonic bath (CPX Series Ultrasonic Bath, Fisherbrand). 15-337-403NA
Ex Vivo Testing Materials 
         Quantity & price per electrode
Data acquisition platform and softwareDigitalLynx 4sX Base Cheetah version 6.0 (Neuralynx Inc.) NAEMG acquisition hardware and software
Electrode interface board (EIB)EIB, EIB16-QC, Neuralynx Inc.31-0603-0007NA
Signal generator5 MHz Function Generator, B&K Precision  4005DDS220V$387.46
PotentiostatPGSTAT1 potentiostat (EcoChemie, Utrecht, Netherlands)NANA
Stainless steel screwFine Science Tools19010-00$98
Ex Vivo Testing Materials 
         Quantity & price per electrode
Rodent treadmill Exer 3/6 Open Treadmill, Columbus InstrumentsNANA
Dental cementExcel Formula® Pourable Dental Material, St. George Technology Inc.#24211$125.60
Light microscopeKeyence BZ-X800, Keyence Corporation, Osaka, Japan NANA
Motion capture systemOptitrack Color Camera, Optitrack, NaturalPoint Inc.NANA
Peak detection algorithm“SciPy.signal.find_peaks - SciPy v1.8.1 Manual”, 2022NANA
Python softwarePython Software Foundation. Python Language Reference, version 3.9. Available at http://www.python.orgNANA
RatHsdBlu: LE, Envigo140NA
Statistical sotwareGraphPad Prism version 10.0.0 (GraphPad Software, Boston, Massachusetts USA)NANA

References

  1. Grandjean, P. A., Mortimer, J. T. Recruitment properties of monopolar and bipolar epimysial electrodes. Ann. Biomed. Eng. 14 (1), 53-66 (1986).
  2. Memberg, W. D., Stage, T. G., Kirsch, R. F. A fully implanted....

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Low costEpimysialElectromyographyElectrodeFabricationTestingEMGImplantablePlatinum iridiumSiliconeStainless SteelEx VivoIn VivoImpedanceBiocompatibilityVastus LateralisRat

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