Laser etched bifilar fine wire electrode for skeletal muscle motor unit recording

To selectively record a limited number of skeletal muscle motor unit action potentials, a bifilar fine wire electrode was developed. Two 8 micrometers wires were braided together, a hook formed, and ends insulated. A round beam, pulsed laser, etched a 5 micrometers piece of insulation from each wire near the hooked end. Bipolar recordings from a select number of skeletal muscle motor units were obtained from these two uninsulated 5 micrometers areas. Reactive and capacitative components for each set of electrodes were measured. These electrodes were selective in recording from 3 to 5 single motor unit action potentials at low isometric tension levels.