A Water-In-Air Droplet Microfluidic System Toward a Self-Powered Bio-Detection Platform Using Liquid Solid Triboelectric Nanogenerator

Liquid–solid triboelectric nanogenerators (LS-TENGs) provide a unique opportunity to develop self-powered and non-invasive sensing systems within microfluidic environments. In this work, we establish a droplet microfluidic platform based on water-in-air droplet generation, enabling precise control of discrete droplets and their interaction with triboelectric interfaces. When droplets pass through the microchannel and slide over the solid surface, electron–ion hybrid charge transfer occurs according to the recently proposed two-step liquid–solid contact electrification mechanism. The resulting electrostatic induction on embedded electrodes produces well-defined voltage pulses that directly reflect droplet passage events. Rather than relying on optical detection, external power sources, or intrusive electrodes, our system leverages LS-TENG as the primary sensing principle, achieving droplet detection through the intrinsic triboelectric response at the water–solid interface. This design not only simplifies the sensing architecture but also broadens the applicability of droplet microfluidics to scenarios where optical access is limited or electrical isolation is required. Furthermore, the system demonstrates sensitivity to changes in solution composition, aligning with recent studies showing LS-TENG’s capability in liquid-phase chemical monitoring. Overall, this work presents a foundational demonstration of an LS-TENG-based microfluidic detection platform, establishing a versatile route toward self-powered droplet monitoring and future biochemical or physicochemical sensing applications within microfluidic systems.