Plantar pressure detection with mechanically induced long period fiber grating system

We demonstrate an application of the mechanically induced long period fiber grating system for a foot plantar measurement. The system is designed as a fixed fiber grating platform that can be utilized for monitoring a subject's foot plantar pressure distribution in static and dynamic activities. The pressure information obtained from the foot loading characteristics can be used for various application such as disease diagnosis of foot problem, foot ware design, sport biomechanics and injury prevention. The system is composed of a strand of a single mode fibers with 800 nm cut off wavelength and circular plastic grooved plates with the grating period of 0.8 and 1.0 mm made by 3 D printing. The sensing units are fixed at biomechanically significant positions; fore-foot, mid-foot and hind-foot of the foot platform for monitoring the foot plantar pressure distribution. The sensing locations are chosen appropriately to contact with sensitive areas of foot and can initially provide enough foot plantar pressure characteristics of a subject. The fiber sensing units with grating having different periods provides different sets of transmission spectra which separately respond to individual perturbed points. Preliminary result shows that the system can be used to classify different types of foot. With some advantageous properties of the optical fiber such as structural flexibility and light weight, the system can successfully be used to monitor the static and dynamic perturbations such as the movement of the body center of mass and foot actions in the stance phase. The study has demonstrated that the proposed fiber-optic sensing systems has a feasibility of being used as an alternative for insole plantar pressure detection systems.