Surface Electromyography Controlled Human-Machine Interface Using Upcycled Compact Disc Electrodes

In efforts of relieving the ever-amassing amounts of electronic waste produced a year, researchers are looking for ways to repurpose discarded devices into new technologies for biomedical purposes. Promising methods of repurposing compact discs (CDs) into stretchable and flexible biosensors called upcycled compact disc electrodes (UCDEs), have opened up new possibilities for providing accessible and affordable biotechnology for a variety of applications. One application is the implementation of UCDEs in human machine interfaces (HMI). Human controlled robotic interfaces have garnered growing interest in recent years due to its potential use in aiding disabled and elderly individuals or augmenting the performance of everyday tasks and occupations. This study focuses on creating an HMI to simulate hand movement based on surface electromyography (EMG) conducted with UCDE applications. The UCDEs are specifically designed and patterned to mimic the mechanical properties of the skin above the targeted muscles and are used to detect the electroactivity during contraction and relaxation. When integrated into an HMI, UCDEs have proven to be capable of consistent and reliable measurements of muscle detection capable of controlling the robotic interface.<br/>To begin the UCDE fabrication process, Verbatim UltraLife Gold Archival Grade DVD-R CDs were soaked in acetone for 30 seconds to break down the polycarbonate substrate and release the metal layer. The metal was then mechanically harvested by adhering polyimide tape followed by a layer of water-soluble tape to the surface of the exposed metallic surface. At this stage, the metal is patterned using a Cricut Fabric Cutter and prepared to be integrated into the machine interface. Mechanical properties of the UCDEs were evaluated using tensile testing with a 25 N load at a 5.1 mm/min to failure and cyclic bending with a strain rate of 300 mm/min held at a bending radius of 3.5 mm. The Quad BioAmp PowerLab system was used to examine the material’s capability of EMG measurements and find optimal UCDE placement for the machine interface. The HMI used in this study was built using the InMoov open-source 3D printed hand and forearm, powered by an Arduino Nano and wirelessly controlled with a nRF24 module. MyoWare 2.0 Muscle Sensors attached to the UCDE sensors were used for measuring and processing muscle activity that can then be used to control movement of the robotic hand and designed into a wireless wearable electronic device. The machine interface was connected and coded to utilize the signals from the muscle sensors using Arduino Software (IDE).<br/>The polymeric-metal layers of the UCDE were patterned with ease using the mechanical cutter down to feature sizes of 25 μm capable of up to 20% strain. Once patterned, the UCDEs demonstrated an elastic modulus of 5.59 ± 0.16 MPa and elongation of 62.35 ± 1.81% when tested to failure. Cyclic bending for 100 cycles with a radius of 3.5 mm demonstrated a 0.29% increase in UCDE resistance. The performance of the UCDEs have proved to be comparable to commercial electrodes when measuring EMG of various muscle groups. When integrating UCDEs with the HMI, the wearable electronic system and UCDEs were attached in ideal placement on the forearm. UCDEs proved capable of controlling all five robotic fingers in three distinct motions by detecting EMG signals from three different muscle groups simultaneously within a small surface area. Performance of the machine interface was comparable between the use of UCDEs and commercially available electrodes.<br/>UCDEs proved to be capable of controlling complex systems such as HMIs through the constant measurement of EMG signals. This discovery demonstrates the promising potential of this sustainable solution for upcycling electronic waste and the possibility of creating more accessible and affordable HMIs with the use of commonly available materials.