Life and Health Sciences Research Institute (ICVS), School of Health Sciences, University of Minho, Braga, Portugal.
Med Eng Phys. 2012 Sep;34(7):972-81. doi: 10.1016/j.medengphy.2011.11.002. Epub 2011 Dec 5.
This paper presents a complete non-invasive Wireless acquisition system based on dry electrodes for electroencephalograms (WiDE-EEG) with emphasis in the electronic system design. The WiDE-EEG is composed by a 2.4 GHz radio-frequency (RF) transceiver, biopotential acquisition electronics and dry electrodes. The WiDE-EEG can acquire electroencephalogram (EEG) signals from 5 unipolar channels, with a resolution of 16 bits and minimum analog amplitude of 9.98 μV(pp), at a sampling rate of 1000 samples/s/channel and sends them to a processing unit through RF in a 10 m range. The analog channels were optimized for EEG signals (with amplitudes in the range 70-100 μV) and present the following characteristics: a signal gain of 66 dB and a common mode rejection ratio of 56.5 dB. Each electrode is composed by 16 microtip structures that were fabricated through bulk micromachining of a <100>-type silicon substrate in a potassium hydroxide (KOH) solution. The microtips present solid angles of 54.7°, a height of 100-200 μm and 2 μm spaced apart. The electrodes have a thin layer (obtained by sputtering) of iridium oxide (IrO) to guaranty their biocompatibility and improve the contact with the skin. These dry electrodes are in direct contact with the electrolyte fluids of the inner skin layers, and avoid the use of conductive gels. The complete WiDE-EEG occupies a volume of 9 cm×8.5 cm×1 cm, which makes it suitable for true mobility of the subjects and at the same time allows high data transfer rates. Since the WiDE-EEG is battery-powered, it overcomes the need of galvanic isolation for ensuring patient safety observed on conventional EEG instrumentation systems. The WiDE-EEG presents a total power consumption of 107 mW, divided as follows: the acquisition system contributes with 10 mW per channel, whereas the commercial MICAz module contributes with 57 mW (e.g., 24 mW from the microcontroller and 33 mW from the RF chip). The WiDE-EEG also presents autonomy of about 25 h with two class AA 1.5 V batteries.
本文提出了一种完整的基于干电极的非侵入式无线脑电信号采集系统（WiDE-EEG），重点介绍了电子系统设计。WiDE-EEG 由 2.4GHz 射频（RF）收发器、生物电位采集电子设备和干电极组成。WiDE-EEG 可以从 5 个单极通道采集脑电图（EEG）信号，分辨率为 16 位，最小模拟幅度为 9.98μV（pp），采样率为 1000 样本/s/通道，并通过 RF 在 10m 范围内将其发送到处理单元。模拟通道经过优化，可用于 EEG 信号（幅度在 70-100μV 范围内），具有以下特点：信号增益为 66dB，共模抑制比为 56.5dB。每个电极由 16 个微尖结构组成，这些微尖结构通过在氢氧化钾（KOH）溶液中对<100>-型硅衬底进行体微加工制造而成。微尖的立体角为 54.7°，高度为 100-200μm，间隔为 2μm。电极有一层薄的氧化铱（IrO）层（通过溅射获得），以保证其生物相容性并改善与皮肤的接触。这些干电极直接与内层皮肤的电解质液接触，避免使用导电凝胶。完整的 WiDE-EEG 体积为 9cm×8.5cm×1cm，这使其适合受试者的真正移动性，同时允许高数据传输速率。由于 WiDE-EEG 由电池供电，因此克服了传统 EEG 仪器系统中为确保患者安全而需要进行电流隔离的问题。WiDE-EEG 的总功耗为 107mW，分为以下几部分：采集系统每个通道贡献 10mW，而商业 MICAz 模块贡献 57mW（例如，微控制器贡献 24mW，RF 芯片贡献 33mW）。WiDE-EEG 还使用两节 AA 1.5V 电池，可提供约 25 小时的自主运行时间。
