Design and development of dry microneedles electrode-based portable wireless instrumentation system for EEG acquisition

Abstract

A polymer dry microneedles electrode (DME) based portable multi-channel wireless electroencephalogram (EEG) acquisition system was developed in this work. The DME and its electronics were developed as an alternative acquisition methodology to the conventional wet electrode method, which requires skin preparation and application of gels to reduce the skin-electrode contact impedance. In order to overcome the aforesaid issues, dry microneedles electrodes were micromachined of size with base diameter 120 µm, tip diameter ranging between 5-10 µm and height 180-200 µm using biocompatible polymer, polymethyl methacrylate (PMMA) pellet and coated with metallic and metal nitride films to a total deposited film thickness ranging between 800-850 nm, those were both biocompatible and conductive. The proposed instrumentation system includes an EEG sensing circuitry comprising filters, amplifiers, an analogue processing unit, a digital signal processing circuit comprising microcontroller and a Bluetooth wireless transmission module for loss-free signal transmission preventing signal distortion and cable noise. The developed electrodes were characterised for their electrical properties to acquire EEG signals from the frontal lobe of the brain. The performance of the developed electrodes was evaluated with respect to conventional wet electrodes using developed wireless instrumentation system and found that the amplitude and frequency response of both electrode systems had an average correlation and coherence of more than 90% proving that DME could be a futuristic alternative to conventional EEG acquisition systems.