The human body’s vascular system is a finely regulated network: blood vessels can change in shape (i.e. constrict, or dilate), their elastic response may shift and they may undergo temporary and partial blockages due to pressure applied by skeletal muscles in their immediate vicinity. Simultaneous measurement of muscle activation and the corresponding changes in vessel diameter, in particular at anatomical regions such as the face, is challenging, and how muscle activation constricts blood vessels has been experimentally largely overlooked. Here we report on a new electronic skin technology for facial investigations to address this challenge. The technology consists of screen-printed dry carbon electrodes on soft polyurethane substrate. Two dry electrode arrays were placed on the face: One array for bio-potential measurements to capture muscle activity and a second array for bio-impedance. For the bio-potential signals, independent component analysis (ICA) was used to differentiate different muscle activations. Four-contact bio-impedance measurements were used to extract changes (related to artery volume change), as well as beats per minute (BPM). We performed concurrent bio-potential and bio-impedance measurements in the face. From the simultaneous measurements we successfully captured fluctuations in the superficial temporal artery diameter in response to facial muscle activity, which ultimately changes blood flow. The observed changes in the face, following muscle activation, were consistent with measurements in the forearm and were found to be notably more intricate. Both at the arm and the face, a clear increase in the baseline impedance was recorded during muscle activation (artery narrowing), while the impedance changes signifying the pulse had a clear repetitive trend only at the forearm. These results reveal the direct connection between muscle activation and the blood vessels in their vicinity and start to unveil the complex mechanisms through which facial muscles might modulate blood flow and possibly affect human physiology.

中文翻译：

---

用于同时研究面部生物电位和生物阻抗的软电极

人体的血管系统是一个精细调节的网络：血管可以改变形状（即收缩或扩张），它们的弹性反应可能会改变，并且由于紧邻的骨骼肌施加的压力，它们可能会经历暂时和部分阻塞。同时测量肌肉激活和血管直径的相应变化，特别是在面部等解剖区域，具有挑战性，并且肌肉激活如何收缩血管在实验上很大程度上被忽视了。在这里，我们报告了一种用于面部研究的新型电子皮肤技术，以应对这一挑战。该技术由软质聚氨酯基材上丝网印刷的干碳电极组成。将两个干电极阵列放置在脸上：一个阵列用于生物电势测量以捕获肌肉活动，第二个阵列用于生物阻抗。对于生物电信号，独立成分分析（ICA）用于区分不同的肌肉激活。使用四接触点生物阻抗测量来提取变化（与动脉体积变化相关）以及每分钟心跳数 (BPM)。我们同时对面部进行生物电位和生物阻抗测量。通过同时测量，我们成功捕获了颞浅动脉直径随面部肌肉活动而变化的波动，最终改变了血流。肌肉激活后观察到的面部变化与前臂的测量结果一致，并且发现明显更加复杂。在手臂和面部，在肌肉激活（动脉变窄）期间记录到基线阻抗明显增加，而阻抗变化表明脉搏仅在前臂有明显的重复趋势。这些结果揭示了肌肉激活与其附近血管之间的直接联系，并开始揭示面部肌肉调节血流并可能影响人体生理的复杂机制。