Research On Implantable Flexible Intraocular Pressure Sensor And Its Measure-control Technology

Intraocular pressure(IOP)is a very important physiological signal that needs to be accurately and real-time monitored for glaucoma patients,especially for severe ones.Because of the large size,lack of continuous monitoring,need of assistance measurements and other factors,common intraocular pressure measuring instruments in hospital cannot meet the requirement to accurately and conveniently measuring IOP all time around.Therefore,this paper proposes an implantable flexible intraocular pressure sensor for glaucoma patients to realize long time and continuous IOP monitoring.The working principle,structure design,fabrication,measure-control system,performance test and characterization test of the sensor are studied deeply.Firstly,after analyzing and summarizing the current situation and development trend of implantable intraocular pressure sensors and flexible pressure sensors,a capacitive pressure sensor used for intraocular pressure measurement is proposed.The sensor,fabricated with micro-nano contact structure,has many advantages,such as high sensitivity due to its easy deformation and large variation of dielectric constant.According to its working principle,structure design and implantable special application,biocompatible materials and two kinds of methods about the fabrication of the sensor are chosen and studied in this paper.One method is using regular pyramid structure and the other is using multi-walled carbon nanotubes to prepare the micro-nano contact structure.After balancing the pros and cons of the two methods,this paper mainly focuses on the fabrication of sensor using multi-walled carbon nanotubes.Secondly,measurement and control system of the sensor is another important part of this paper,which is mainly composed of sealed cavity,environmental control module and signal processing module.In order to simulate the intraocular pressure environment,an environment control module is involved in the system to control the pressure and temperature.Besides,the signal processing module comprises capacitance detection circuit and electronic measuring instrument,for detecting signal of the sensor.To extend the application field of the sensor,a pressure measurement system is designed and manufactured,which is used for the response of the sensor to solid pressure.The measure-control system can meet the requirements of performance test and simulation of intraocular pressure environment.Finally,the performance of the sensor based on micro-nano contact structure is tested by a high precision measuring instruments and measure-control system.The results show that the sensor has good stability,repeatability,hysteresis and its sensitivity can reach 1.3 / kPa.In addition,the response time of the sensor to change of micro pressure reaches milliseconds and the sensor is insensitive to change of temperature.After suitable encapsulation,the pressure sensor with micro-nano contact sensitive structure can be used for the measurement of intraocular pressure.This kind of high performance implantable flexible intraocular pressure sensor will effectively promote the application of new micro sensors in medical,health monitoring,mobile health services and other fields.