A physical action potential generator: design, implementation and evaluation.

Malcolm A Latorre,Karin Wårdell,Adrian D C Chan

doi:10.3389/fnins.2015.00371

Abstract

The objective was to develop a physical action potential generator (Paxon) with the ability to generate a stable, repeatable, programmable, and physiological-like action potential. The Paxon has an equivalent of 40 nodes of Ranvier that were mimicked using resin embedded gold wires (Ø = 20 μm). These nodes were software controlled and the action potentials were initiated by a start trigger. Clinically used Ag-AgCl electrodes were coupled to the Paxon for functional testing. The Paxon's action potential parameters were tunable using a second order mathematical equation to generate physiologically relevant output, which was accomplished by varying the number of nodes involved (1–40 in incremental steps of 1) and the node drive potential (0–2.8 V in 0.7 mV steps), while keeping a fixed inter-nodal timing and test electrode configuration. A system noise floor of 0.07 ± 0.01 μV was calculated over 50 runs. A differential test electrode recorded a peak positive amplitude of 1.5 ± 0.05 mV (gain of 40x) at time 196.4 ± 0.06 ms, including a post trigger delay. The Paxon's programmable action potential like signal has the possibility to be used as a validation test platform for medical surface electrodes and their attached systems.

Highlights

There has been an increased use of electrodes for electrophysiological signal acquisition in health care and biomedical research (Kelly et al, 2007; Pedrosa et al, 2012; Chen et al, 2013; Rieger et al, 2014)
Our overarching goal is to develop an action potential (AP)-like generator that is loosely modeled on a segment of a single axon of a generic myelinated nerve that can serve as a test platform for electrodes without the reliance on tissues
Only 40 nodes of Ranvier were mimicked, each node being represented by a gold wire (Ø = 20 μm, 99.99% Au, SPM, Armonk NY, USA) and each wire was connected to a separate MOSFET electronic driver circuit which was in turn individually connected to a unique I/O pin from an ATxmega64A1 CPU (Atmel Corp., USA)

Summary

Introduction

There has been an increased use of electrodes for electrophysiological signal acquisition in health care and biomedical research (Kelly et al, 2007; Pedrosa et al, 2012; Chen et al, 2013; Rieger et al, 2014). There are few reliable testing platforms that emulate the native physiological conditions found in biological sources. Biological tissues such as nerves, are inherently heterogeneous, and ensuring tissue culture survival throughout the testing period is challenging. Our overarching goal is to develop an action potential (AP)-like generator that is loosely modeled on a segment of a single axon of a generic myelinated nerve that can serve as a test platform for electrodes without the reliance on tissues. An example would be electrodes designed to record peripheral nerve action potentials. The physical hardware and proof-of-concept model development were explored

Methods

Results

Conclusion