We have developed fabric biomedical electrode array where silver paste, conductive polymer and ionic liquid gel are printed and insulation layers are formed with hot melt film on the fabric substrate.
Recently, wearable electronic devices such as Microsoft Hololens, google glass, sportsband, or other tools have been developed and commercialized for human healthcare monitoring and information tools. Among wearable electronic devices, wearable ECG or EMG electrodes are promising for human motion sensing tools. Especially for monitoring human hand or foot motion sensing, the biomedical electrode array which is made of fabric is necessary.
To make biomedical electrodes array, new fabrication process of fabric multilayer electrodes which consists of biomedical electrode parts to contact human skin and the wiring parts from biomedical electrodes parts to the amplifiers are required. Previous study (S. Takamatsu,et.al., "Direct patterning of organic conductors on knitted textiles for long-term electrocardiography," Scientific Reports, vol. 5, 15003(7pp), Oct 2015.) reports single layer fabric electrodes, but the multilayer electrodes has not been fabricated on the fabric and the biomedical electrode array has not been achieved. The most difficult fabrication process to make multilayer electrodes is to construct insulation layer between multiple electrode because most of the insulation inks are dissolved by the solvent of second layer electrode ink(i.e., toluene), or dissolve the first layer electrode with the solvent of the insulation ink. Our new fabrication process of fabric multilayers consists of the electronic ink printing and hot-melt film sticking on the fabric. Laser cut hot melt film is placed on the electrode printed film and heated to stick to the film as insulation layer. Hot melt film has the advantages in which the hot melt film is not dissolved in the solvent of inks and can combine several layers of functional fabric and films.
The developed fabrication process of fabric biomedical electrode array with printable electronic ink and hot-melt film for Electromyography is following steps. 1. Silver paste wiring electrode is printed on the stretchable polyurethane film. 2. Laser cut hot melt film is placed on the electrode and heated. 3. The patterned urethane film is attached on the knit fabric with hot melt film. 4. Conductive polymer of PEDOT PSS and ionic liquid gel is patterned on another knit fabric for making biomedical electrode part. 5. Wiring part fabric and biomedical electrode fabric are attached by hot melt film and glue. By using our process, the 2x5 array biomedical electrode which has 1cm2 biomedical electrodes parts and 0.5 mm wide wiring can be successfully fabricated. The impedance between electrodes and human skin is less than 1 MOhm, which is useful for EMG monitoring. Thus, our process will useful for wearable multi array of EMG measurement.