  Underneath the ear skin there are richly branching vascular and neural
networks that ultimately connecting to our heart and brain. Hence, the
three-dimensional (3D) mapping of auricular electrophysiological signals could
provide a new perspective for biomedical studies such as diagnosis of
cardiovascular diseases and neurological disorders. However, it is still
extremely challenging for current sensing techniques to cover the entire
ultra-curved auricle. Here, we report a graphene-based ear-conformable sensing
device with embedded and distributed 3D electrodes which enable full-auricle
physiological monitoring. The sensing device, which incorporates programable 3D
electrode thread array and personalized auricular mold, has 3D-conformable
sensing interfaces with curved auricular skin, and was developed using one-step
multi-material 3D-printing process. As a proof-of-concept, spatiotemporal
auricular electrical skin resistance (AESR) mapping was demonstrated. For the
first time, 3D AESR contours were generated and human subject-specific AESR
distributions among a population were observed. From the data of 17 volunteers,
the auricular region-specific AESR changes after cycling exercise were observed
in 98% of the tests and were validated via machine learning techniques.
Correlations of AESR with heart rate and blood pressure were also studied using
statistical analysis. This 3D electronic platform and AESR-based new
biometrical findings show promising biomedical applications.
