Application Of Planter Pressure Monitoring System Based On Polyvinylidene Flouride Piezoelectric Film In Medical Gait Analysis

Plantar pressure refers to the pressure field created between the sole of the foot and the supporting surface during daily activities.The quantitative research of plantar pressure distribution has a wide range of applications not only in posture research,footwear design,etc.,but also in medical gait analysis.It is also crucial and can be used to diagnose lower extremity disorders,balance disorders,sports injuries,etc.With the rapid development of health care testing equipment,micromanufacturing process and wireless communication technology,the development of medical and health care sensors in the direction of miniaturization,light weight,and energy saving has attracted more and more attention.Therefore,in the quantitative research of plantar pressure distribution,an effective solution can be provided based on the piezoelectric effect.In this paper,based on the piezoelectric effect,a polymer piezoelectric material,polyvinylidene fluoride(PVDF)piezoelectric film,was selected as the main body of the sensor,and a mature and reliable flexible circuit board(FPCB)processing technology was used to design a self-power sensor with good durability and excellent stability.And the wearable self-actuated plantar pressure sensing system was more convenient and comfortable to use.By collecting the data of gait analysis such as plantar pressure distribution and motion parameters of the human body during exercise,the quantitative test of plantar pressure was realized.The main research contents of this paper can be described as follows:(1)Firstly,the material properties were studied,and according to the research results,materials suitable for foot pressure sensing were selected.The electrical output properties and durability(the durability test reaches 1 million times)of PVDF,a piezoelectric polymer material with different thicknesses,were experimentally studied.And by Fourier Transform Infrared Spectroscopy(FTIR),a microscopic level study was carried out to calculate the proportion of β crystal phase in the film.The final results showed that as the thickness of the film increased,the proportion of its β crystal phase also increased,and its output voltage also increased.Taking into account the thickness and output performance of the film,a PVDF film with a thickness of 110 μm was finally selected as the fabrication material of the sensor.(2)The preparation and packaging of the sensor in the foot pressure monitoring system and the output characteristics of the sensor after packaging were studied.On the basis of theoretical research and analysis,how to prepare the encapsulated foot pressure insole was introduced first,and experiments and researches were carried out on the temperature,humidity and durability of the encapsulated sole pressure sensor.After experimental tests,the pressure sensor had a measurement range of 200 KPa,and had good temperature and humidity performance and durability.Finally,the information transmission system and usage of the foot pressure monitoring system were briefly introduced.(3)Finally,the practical application of the foot pressure monitoring system.The foot pressure distribution data of different exercise states,healthy people and patients were collected using the foot pressure monitoring system.And using MATLAB calculated the kinematic parameters in the gait analysis such as pace,cadence,etc.,through the foot pressure data.Then,machine learning was used to classify and identify the foot pressure of different exercise states and different people.In this experiment,the plantar pressure data of more than 70 healthy subjects and 70 patients with lumbar stenosis were collected.Through machine learning,foot pressure data can be used to identify different motion states with an accuracy close to 100%,and the accuracy rate of data identification for patients with lumbar stenosis can reach 99%.In this paper,the relationship between the output performance and thickness of PVDF films was studied from two aspects: macroscopic output appearance and microscopic crystal phase ratio.Then,a wearable self-powered planter pressure monitoring system with simple structure,convenient use,ultra-high robustness and excellent resistance to temperature and humidity interference was designed using this material.The system realized real-time acquisition of the distribution of the planter pressure of a person moving in a natural state.And combined with machine learning,the planter pressure data of different exercise states and subjects’ health state were classified,learned and recognized.It realized the discrimination of exercise state and health state through the distribution of planter pressure.Therefore,the planter pressure monitoring system studied in this paper can be used for sports monitoring of athletes,to achieve healthy and scientific intelligent sports management,and can also be applied to the diagnosis of patients in clinical medicine,providing more basis for the diagnosis of doctors.