Significant fluctuations in body fluid pH can indicate the onset of infection or a chronic condition. In this paper, a hydrogel-activated circular discrete interdigitated capacitive (D-IDC) biosensor is introduced for monitoring the acidity of biological fluids. The pH-sensitive transducer is a thin biocompatible chitosan/polyvinyl alcohol hydrogel disk positioned at the center of a multi-terminal D-IDC comprised of numerous distinct circular conductive electrodes covering the active sensing area. The D-IDC is printed on Nylon-66 filter paper that has been coated with a thin layer of polydimethylsiloxane (PDMS). The circular electrode pattern is printed on the PDMS surface using nontoxic graphene/carboxymethyl cellulose (G-CMC) aqueous suspensions as the electrically conductive ink. A thin polymer passivation layer is then spin coated on the surface of the G-CMC conductive electrodes to prevent an electrical short with the liquid filled hydrogel transducer. The pH level of the fluid causes the centrally located hydrogel transducer to swell/de-swell over the circular electrodes producing an incremental change in the measured capacitance. A prototype comprised of seven electrode pairs is fabricated and experimentally tested under controlled conditions using phosphate buffer solutions (PBS) with varying pH. The operational and analytical parameters of the hydrogel-activated biosensor are evaluated in terms of measured capacitance. The prototype sensor demonstrates acceptable repeatability (SD < 0.4%) and reproducibility (SD < 5.8%). Sensor resolution can be modified by reducing the physical size of the electrode micro-traces used in the D-IDC design and increasing the number electrode pairs.

中文翻译：

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用于监测生物液体 pH 值的一次性水凝胶活化圆形叉指传感器

体液 pH 值的显着波动可能表明感染或慢性病的发作。在本文中，介绍了一种水凝胶激活的圆形离散叉指电容 (D-IDC) 生物传感器，用于监测生物体液的酸度。pH 敏感传感器是一个薄的生物相容性壳聚糖/聚乙烯醇水凝胶盘，位于多端 D-IDC 的中心，由覆盖有源传感区域的许多不同的圆形导电电极组成。D-IDC 印在 Nylon-66 滤纸上，滤纸上涂有一层薄薄的聚二甲基硅氧烷 (PDMS)。圆形电极图案使用无毒石墨烯/羧甲基纤维素 (G-CMC) 水性悬浮液作为导电油墨印刷在 PDMS 表面上。然后在 G-CMC 导电电极的表面旋涂一层薄的聚合物钝化层，以防止与充满液体的水凝胶换能器发生电短路。流体的 pH 值导致位于中心的水凝胶换能器在圆形电极上膨胀/去膨胀，从而产生测量电容的增量变化。一个由七个电极对组成的原型是在受控条件下使用不同 pH 值的磷酸盐缓冲溶液 (PBS) 制造和实验测试的。水凝胶激活的生物传感器的操作和分析参数根据测量的电容进行评估。原型传感器展示了可接受的重复性 (SD < 0.4%) 和再现性 (SD < 5.8%)。