Pressure Detection And Finite Element Analysis Of Carbon Nanotube Arrays

With the development of microelectronic devices towards to miniaturization,diversification and high frequency,the resulted excessive heat density within the device has brought severe and inevitable influences on the life and stability of device applications.Therefore,it is of great significance to search for thermal materials with low thermal resistance and high thermal conductivity.Carbon nanotubes(CNTs)possess both excellent mechanical and thermal properties,and are expected to be promising heat management materials with respect to heat dissipation of the device.In the applications of thermal interface materials,CNT arrays are inevitably under stress in different degrees,therefore,it is of great importance to investigate how the stress affects the thermal properties of CNT arrays.In this paper,the pressure detection system is designed for the measurement of the thermal properties of CNT arrays using a transient thermal reflection technique based on a bi-directional heat flow model.The finite element method is applied to analyze the stress distribution on the surface of CNT arrays as well as the relationships between the surface stresses of CNT arrays and the detection values by the pressure sensor.On the basis of core STM32,the pressure detection system is designed with a detection accuracy of 0.1lb.Using the inverting phase amplifier circuit as the pressure signal conversion circuit,the processed signals are uploaded to the host computer through the USB or nine-pin serial port.The relationships between the sensor conductivity and the stress applied under different clamping voltages are calibrated,and the value of the pressure sensor can be detected by this system,which satisfies the need for pressure detection in the experimental system for measuring the thermal properties of CNT arrays using a transient thermal reflection technique based on a bi-directional heat model.The open-hole steel structure is adopted in order to compress the CNT arrays,which necessitates taking the possible influence of the stress on the CNT arrays into consideration.Based on the characteristics of open-cell foam model and hardening elastoplastic materials,the stress distribution on the surface of the CNT arrays for 190?m and 650?m as well as the stress distribution of the pressure sensor are analyzed by the Comsol Multiphysics software.The results show that no significant effect on the stress distribution of the CNT arrays is observed when only the vertical stress tensor is considered.We believe that the surface stress of the CNT arrays is approximately equal to the detection value of the pressure sensor under small stress while the surface stress of the CNT arrays is slightly larger than the detection value when large stress is applied.