We present DropleX, the first system that enables liquid sensing using the capacitive touchscreen of commodity tablets. DropleX detects microliter-scale liquid samples, and performs non-invasive, through-container measurements for liquid analysis. These capabilities are made possible by a physics-informed mechanism that disables the touchscreen's built-in adaptive filters, originally designed to reject the effects of liquid drops such as rain, without any hardware modifications. We model the touchscreen's sensing capabilities, limits, and non-idealities to inform the design of a signal processing and learning-based pipeline for liquid sensing. Our system achieves 89-99% accuracy in detecting microliter-scale adulteration in soda, wine, and milk, 94-96% accuracy in threshold detection of trace chemical concentrations, and 86-96% accuracy in through-container adulterant detection. These exploratory results demonstrate the potential of repurposing commodity touchscreens as a liquid characterization platform for laboratory settings, food and beverage testing, and chemical analysis applications.

翻译：本文提出DropleX系统，这是首个利用商用平板电容式触摸屏实现液体传感的技术。DropleX能够检测微升级液体样本，并通过非侵入式的穿容器测量方式进行液体分析。该能力通过一种物理信息机制实现，该机制在不修改硬件的前提下，禁用了触摸屏内置的、原本用于消除雨滴等液体干扰的自适应滤波器。我们通过建模分析触摸屏的传感能力、局限性与非理想特性，以此指导基于信号处理与机器学习的液体传感流程设计。本系统在检测苏打水、葡萄酒和牛奶中的微升级掺杂时达到89-99%准确率，痕量化学物质浓度阈值检测达到94-96%准确率，穿容器掺杂检测达到86-96%准确率。这些探索性结果表明，将商用触摸屏改造为液体表征平台在实验室环境、食品饮料检测及化学分析领域具有应用潜力。