High sensitive Polyimide-based single-walled carbon nanotube thermal film sensor for fluid shear stress measurements

Abstract

A flexible polyimide-based single-walled carbon nanotube (SWCNT) thermal film sensor has been developed for wall shear stress measurements in both air and water. To ensure high sensitivity, vacuum thermal annealing and electrical aging are conducted to enhance the electric properties of the sensor with low-resistance and the high temperature coefficient of resistivity (TCR). The TCR of sensors can reach to 8040 ppm/°C to the author's knowledge, which is the highest reported value of thermal sensors used for shear stress measurements. In calibration, the output voltage of the sensor is proportional to the one third power of wall shear stress with the sensitivity on the order of mV Pa −1 in the constant current operation mode. The repeatability error is no more than 1% in both air and water, which confirms the capability of the flexible SWCNT thermal film sensor for fluid wall shear stress measurements with high sensitivity.

Influence of solvents on the enhancement of thermophysical properties and stability of multi-walled carbon nanotubes nanofluid

“…Li et al [11] fabricated a high performance super capacitor using reduced graphene oxide carbon nanotubes which achieved a maximum current density and specific capacitance of 0.2 A g −1 and 101 F g −1 respectively. In a different study, Gao et al [12] experimentally measured the shear stress of a wall with a novel polyimide incorporated SWCNT sensor. Authors reported the highest temperature coefficient resistivity of 8040 ppm/°C that showed a repeatability error of less than 1%.…”

Microfluidic thermal flow sensor based on phase-change material with ultra-high thermal sensitivity

“…2c shows the comparison of TCR values for VO 2 and other temperature-sensitive materials, where the maximum a v (T) in the IMT region shows values more than 60 times higher than conventional metallic thermal sensing materials, such as Pt, 2 which is the material used as the sensing element in most microfluidic thermal flow sensors. It should be noted that although the ultra-high a v (T) can only be obtained in a small temperature window, the room temperature a v (T) still maintains at a high value of À0.024 K À1 , which is comparable to the recently proposed cubic silicon carbide (3C-SiC) 10 and single-walled carbon nanotubes (SWCNTs), 6 and still 6 times higher than Pt. Before analyzing the results of the proposed VO 2 -based thermal flow sensor, it is important to explain its working principle and operation for this particular application.…”

“…In order to improve the sensitivity of thermal flow sensors, consecutive efforts in materials science and nanotechnologies have been made to increase the TCR of non-metal thermal-sensitive materials. With vacuum thermal annealing and electrical aging treatment, both electrical stability and thermal sensitivity of single-walled carbon nanotube (SWCNT) can be significantly improved, 6 leading to a high TCR of 8040 ppm K −1 . In addition, structures of nanowires (NWs) are often used to increase the thermal sensitivity for small temperature fluctuation monitoring.…”

Thermal Conductivity Gas Sensor with Enhanced Flow-Rate Independence

“…Currently, as one of the important detection principles of MEMS sensors, thermal detection has been widely used in fluid sensing fields, especially in gas-related detection, such as gas flow [ 1 , 2 , 3 ], thermal conductivity [ 4 , 5 , 6 ], shear-stress [ 7 , 8 , 9 ], and vacuum [ 10 , 11 , 12 ], etc. Compared to normal chemical sensors, thermal MEMS sensors have the advantages of broad-spectrum, fast response, low power consumption, and long-term stability, becoming a major, long-standing research focus [ 13 , 14 , 15 ].…”