We have combined a graphene field-effect transistor (GFET) and a surface acoustic wave (SAW) sensor on a LiTaO₃ substrate to create a graphene surface acoustic wave (GSAW) sensor. When a SAW propagates in graphene, an acoustoelectric current (I_A) flows between two attached electrodes. This current has unique electrical characteristics, having both positive and negative peak values with respect to the electrolyte-gate voltage (V_Eg) in solution. We found that I_A is controlled by V_Eg and the amplitude of the SAW. It was also confirmed that the GSAW sensor detects changes of electrical charge in solution like conventional GFET sensors. Furthermore, the detection of amino-group-modified microbeads was performed by employing a GSAW sensor in a phthalate buffer solution at pH 4.1. The hole current peak shifted to the lower left in the I_A–V_Eg characteristics. The left shift was caused by charge detection by the GFET and can be explained by an increase of amino groups that have positive charges at pH 4.1. In contrast, the downward shift is thought to be due to a reduction in the amplitude of the propagating SAW because of an increase in the mass loading of microbeads. This mass loading was detected by the SAW sensor. Thus, we have demonstrated that the GSAW sensor is a transducer capable of the simultaneous detection of charge and mass, which indicates that it is an attractive platform for highly sensitive and multifunctional solution sensing.

中文翻译：

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石墨烯表面声波传感器，可同时检测电荷和质量

我们在LiTaO ₃衬底上结合了石墨烯场效应晶体管（GFET）和表面声波（SAW）传感器，以创建石墨烯表面声波（GSAW）传感器。当声表面波在石墨烯中传播时，声电流（I _A）在两个相连的电极之间流动。该电流具有独特的电气特性，相对于溶液中的电解质栅极电压（V _Eg）具有正峰值和负峰值。我们发现I _A受V _Eg控制和声表面波的幅度。还证实了GSAW传感器能够像常规GFET传感器一样检测溶液中的电荷变化。此外，通过在pH 4.1的邻苯二甲酸盐缓冲溶液中采用GSAW传感器进行氨基修饰微珠的检测。空穴电流峰值在I _A – V _Eg中移至左下方特征。左移是由GFET的电荷检测引起的，可以用在pH 4.1处带正电荷的氨基增加来解释。相比之下，向下移动被认为是由于增加的微珠的质量负载而使传播的SAW的幅度减小了。通过SAW传感器检测到此质量负载。因此，我们证明了GSAW传感器是一种能够同时检测电荷和质量的传感器，这表明它是用于高度灵敏和多功能溶液传感的有吸引力的平台。