A Low-Cost Portable Nanophotonic Sensor Based on a Smartphone: A System Readily Available for Many Applications

We present the development of a new low-cost and portable nanophotonic sensor to measure mechanical or environmental quantities, such as acoustic, bending, stretching, or temperature changes (see Figure 1). The sensor consists of a compact diode laser, a multimode fiber, and a smartphone, and thus, it is quite portable. The laser light emitted from the multimode fiber forms optical speckle patterns on a screen. We experimentally implement the bending sensing on a smartphone. The relationship between the bending curvature and the optical speckle pattern is quantitatively studied, demonstrating its feasibility of bending sensing.