“…Generic reusable earpieces, however, are indispensable for commercializing the in-ear EEG system that all users can use immediately in real life. Several kinds of generic earpieces are developed by using memory foam with Ag-coated cloth (Goverdovsky et al, 2016, Goverdovsky et al, 2017Nakamura et al, 2018), Ag spray-coated polycarbonate (Kaveh et al, 2020), CNT/PDMS-based canaltype ear electrode cap (CEE) (Lee et al, 2014), and silvered glass silicone CEE (Dong et al, 2016). Viscoelastic flexibility and pressure between earpiece materials and ear canal allow a device to be held more softly and firmly, reducing both motion artifacts and user discomfort.…”