DropleX: Liquid sensing on tablet touchscreens
This work addresses the need for accessible liquid characterization in laboratory, food testing, and chemical analysis settings, though it is incremental as it repurposes existing hardware.
The researchers tackled the problem of enabling liquid sensing using commodity tablet touchscreens by developing DropleX, a system that detects microliter-scale liquid samples and performs non-invasive, through-container measurements, achieving 89-99% accuracy in detecting adulteration in beverages and 86-96% accuracy in through-container detection.
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. Under controlled laboratory conditions, 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.