| Body temperature is one of the important indicators reflecting human health,and the research on how to accurately monitor human body temperature in real time is of great significance.In this thesis,focusing on the need for wearable devices to accurately monitor human body temperature,the research on flexible thin film temperature sensors was carried out.The flexible thin film temperature sensor was fabricated on flexible polyimide(PI)substrate by sputtering.The strain response was reduced through the graphic of the sensitive layer.Its anti-strain interference ability,temperature sensitivity and dynamic response characteristics were studied.The specific research contents are as follows:Firstly,the structure and performance of the flexible thin film temperature sensor were simulated and analyzed.Using the average thermal stress theory of multi-layer films,the sensitive layer thin film material is platinum,and the thermal stress of thin film temperature sensors constructed on different flexible substrates is calculated and analyzed.The results show that the overall thermal stress of the sensor is the smallest when the polyimide(PI)is used as the flexible substrate.Then,COMSOL Multiphysics was used to design and simulate the graphic of sensitive layer thin films.The results indicate that compared with traditional snake shaped structures,the Peano fractal structure has better ductility and is more suitable for graphical design of sensitive layers.On this basis,the anti-strain capability of the thin film temperature sensor with Peano structure is simulated and analyzed,and its heat transfer process is studied.The results show that the strain resistance of the first-order Peano structure is better with the increase of the arc angle.Moreover,the Peano pattern of the Half-Half structure exhibits a lower response to multi axial strain.And as the order increases,the strain response decreases.The simulation results of the thermal conductivity process show that,under the condition of constant heat source temperature,the time taken for the thin film temperature sensor to reach the temperature of the heat source significantly increases with the increase of PI thickness,and is independent of the heat source temperature.Secondly,on the basis of the simulation results,thin film thermistors with different Peano patterns were fabricated on flexible polyimide substrates.Stress testing was conducted on different samples using a cantilever beam to apply strain.The test results showed that the thin film thermal resistance with a 3-order Half-Half structure had the lowest resistance response to the applied strain,which is consistent with the simulation results.TCR,temperature stability,and bending resistance tests were conducted on the thin film thermal resistance of the 3-order Half-Half structure,and the effect of annealing process on sensor performance was studied.The research results indicate that the samples annealed at 300℃/60 minutes show significant improvements in the above performance aspects.At the same time,the temperature measurement accuracy was improved by constructing a double-line structure,reducing the maximum temperature measurement error to 0.007℃.Finally,dynamic response tests were conducted on the prepared thin film thermal resistor with a 3-order Half-Half structure using water bath method and pulsed laser method respectively.The test results indicate that the time constant measured by the water bath method is in the second level,while the time constant measured by the pulse laser method is in the microsecond level.By analyzing the heat transfer models and processes of different testing methods,the correlation mechanism between the two time constants was discussed. |
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