Abstract Brain-computer interfaces (BCIs) have attracted considerable attention in motor and language rehabilitation.Most silicone-lube devices use cap-based non-invasive, headband-based commercial products or microneedle-based invasive approaches, which are constrained for inconvenience, limited applications, inflammation risks and even irreversible damage to soft tissues.Here, we propose in-ear visual and auditory BCIs based on in-ear bioelectronics, named as SpiralE, which can adaptively expand and spiral along the auditory meatus under electrothermal actuation to ensure conformal contact.Participants achieve offline accuracies of 95% in 9-target steady state visual evoked potential (SSVEP) BCI classification and type target phrases successfully in a calibration-free 40-target online SSVEP speller experiment.Interestingly, in-ear SSVEPs exhibit significant 2nd harmonic tendencies, indicating that in-ear sensing may be complementary for studying harmonic spatial distributions in SSVEP studies.
Moreover, natural speech auditory classification accuracy can reach 84% in cocktail party experiments.The SpiralE provides innovative concepts for designing 3D flexible bioelectronics and assists the development of biomedical Table Lamp Set engineering and neural monitoring.