Low cost portable 3-D printed optical fiber sensor for real-time monitoring of lower back bending

A mechanically robust and compact novel optical fiber sensor system is described to monitor the bending of the lower back bone in both sagittal and frontal planes. Both bending modes are monitored through the change of the coupled optical intensity ratio between three output fibers aligned to one input fiber. This provides real-time feedback to the clinical therapist when different postures are sustained. The output ratio is calibrated against bending angle using an optical setup utilizing a precise rotational stage. The measured data is also correlated to the curvature of the lower back through the implementation of an ad-hoc imaging scheme. Sequences of images are also captured while the optical fiber sensor is attached on the skin surface to the lower back. The imaging system tracks three spots placed on the sensor and skin to trace the angle changes. The optical fiber sensor system has an operational range between −12° to +12°. It is demonstrated that the sensor is suitable for clinical use with the additional benefits of being non-invasive, robust, straightforward to use and low cost. It also allows record of spinal curvature in the home and other real-world settings and potentially reduces the requirement for the use of X-rays and MRI in the clinic.