Flexible Dry Electrodes for Acquiring Electroencephalogram Signals

由于湿电极的缺点，如需要导电凝胶和头皮准备，Avertus Inc.在目前的脑电(EEG)记录耳机中使用了两种不同的干电极。多毛部位的电极配备了直接的大尺寸镀金伸缩销，而非多毛部位的电极则是导电泡沫上的导电纺织品。对于头发稀少的人来说，针状电极会随着时间的推移而感到不舒服，因为针状电极中的弹簧会产生压力。它们在冲击条件下会造成伤害，而针状电极的可伸缩特性使设备变得笨重。此外，使用两种不同的电极会导致阻抗失配问题。在这个项目中，我们将开发一种低成本的柔性导电材料，并用它制作电极。将聚二甲基硅氧烷(PDMS)与导电率为1000 S/m的金属纳米粒子(NPS)制成导电聚合物复合材料(CPC)作为电极材料。毛发和非毛发部位的电极将由CPC制成不同形状的头皮，用于不同轮廓的头皮。为了表征每种电极结构的性能，将测量干燥皮肤与电极之间的接触阻抗。制造的电极将与Avertus的原型耳机集成，并将记录脑电信号。评估长期使用、消毒和多次使用对电极性能的影响。建议的柔性导电干燥电极将使耳机小型化，使其能够舒适和安全地长时间佩戴。将相同的材料用于毛发和非毛发位置的电极将消除当前耳机中的阻抗不匹配问题。

Due to drawbacks of wet electrodes such as the need for conductive gel and scalp preparation, Avertus Inc.uses two different kinds of dry electrodes in the current electroencephalogram (EEG) recording headsets.Electrodes for hairy locations are equipped with straight macroscale gold plated retractable pins, whereaselectrodes for non-hairy locations are a conductive textile over conductive foam. Pin electrode becomeuncomfortable with time for people with thin hair because the springs in the pin electrodes create pressure.They are an injury hazard under impact condition and the retractable nature of the pin electrodes makes thedevice bulky. Moreover, using two different kinds of electrodes causes the impedance mismatch issue. In thisproject, we will develop a low cost flexible conductive material and fabricate electrodes from it. A conductivepolymer composite (CPC) consisting of polydimethylsiloxane (PDMS) and metal nanoparticles (Nps) withconductivity >1000 S/m will be prepared as electrode material. Electrodes for hairy and non-hairy locationswill be produced from the CPC in different shapes for scalps with different contours. To characterize theperformance for each electrode structure the contact impedance between the dry skin and electrode will bemeasured. The fabricated electrodes will be integrated with the Avertus's prototype headset and EEG signalswill be recorded. Effect of long-term usage, sanitization and multiple usage on the electrode performance willbe evaluated. The proposed flexible conductive dry electrodes will miniaturize the headset and allow it to beworn comfortably and safely for long time. The use of same material for hairy and non-hairy locationelectrodes will remove the impedance mismatch issue in the current headset.