Water droplets play a role in Internet of Things applications

Water droplets help life in nature survive, thrive, and evolve. With water droplet serving as one of the indispensable elements in the Internet of Things (IoT), many droplet-oriented technologies, such as microfluidics, droplet manipulation, electrowetting, and energy harvesting, make rapid progress driven by material science, computer science, and medicine. Droplet-based wearable devices are endowed with advantages such as flexibility, sensing ability, and automation for various parameter detection. Besides, the continuous exploration of droplet manipulation has led to the emergence of a wide variety of manipulation methods. Meanwhile, electrowetting that utilizes external fields modifying liquid–solid surfaces has found its applications in various areas, including droplet transportation, microfabrication, and healthcare. The energy generation from water droplets also presents exciting opportunities for the development of novel electricity generators. These approaches for droplet utilization underscore the immense potentials and versatilities of droplet-based technologies in the IoT landscape. Hence, this mini review presents the fundamental droplet-based technologies by summarizing their working mechanisms and methods, device structures, and applications. Given the challenges in materials, fabrication, and system integration, this review shows the overall development roadmap in terms of improved functionality and performance and highlights the opportunities toward multifunctional, self-sustainable, and intelligent systems, which is called for IoT construction.