Abstract: Continuous pressure sensing is important for patients with several different conditions. We provide an implantable sensor, based on microfluidic principles, which in one example has 1 mmHg limit of detection, high sensitivity and excellent reproducibility. This sensor has an optical interface, which enables pressure to be read with, for example, a cell phone camera. The design and fabrication, along with the option of self-monitoring are promising steps toward better patient care and treatment.