Research On Sweat Ion Sensor Based On Flexible ISFET

It was well known that skin was the largest organ of human.The sweat secreted by the sweat glands of the skin is closely related to body fluids and blood.Our sweat carries important physiological information about human health.By non-invasive analysised of sweat components we can got the health status of the human body.The "electronic skin" device with integrated sensors was a hot topic in today’s wearable devices,health monitoring devices,and intelligent robot tactile sensing.Real-time acquisition of sodium ion potassium ion concentration in human sweat through a sweat sensor that can be attached to the surface of the human body is of great significance for athlete training,chronic disease monitoring and drug abuse.Therefore,research on flexible electronic devices with integrated ion sensors has great research value and application value.However,traditional sweat analysis methods such as multi-electrode analysis,electrochemical methods,and colorimetric assays has insurmountable limitations in sweats,because of the composition and environment of sweat are complex,and the mechanical damage of human skinOur works focuses on the preparation of electronic skin sensors,It can specifically recognize ions and has flexible,stretchable properties.In order to obtain a sensor that can detect microelement of sodium and potassium ions in sweat.Based on the principle of ion-selective field-effect transistor(ISFET),our works used an ionic gel as a dielectric layer it has tensile properties.And used the chemical vapor deposition(CVD)grow preparationed few layers of graphene film as the active layer,it has thinning and high electron mobility properties.In this paper,the ion-selective membrane was used to modify the metal gate to make the sensor has specific recognition ability for ions.Using the test solution to test the sweat sensor,we found that the detection limit of this sensor was as low as 0.01 mM/L.Although the device is prepared using a material having tensile properties as much as possible,the tensile properties of the device were still poor.The repeated of stretching and bending of the skin,made our device suffered irreversible damage.Because of the metal electrodes and graphene suffered serious damage.Therefore,we designed the device as an "island-bridge" structure,using a precision cutting process to deal with polyimide film(PI)material as device protection.The PDMS substrate provides better tensile properties of the device.In order to ensure an effective fit of the PI substrate to the PDMS flexible substrate,the device was attached to a polydimethylsiloxane(PDMS)substrate using a bonding process.Finally,through the experiment.It was verified that the device we prepared has excellent ion sensing performance,and the excellent stretchability made it can no feeling attached to the human body surface.