A novel passive wireless ultrasensitive RF temperature transducer for remote sensing

Abstract

A wireless passive ultrasensitive temperature transducer is presented in this paper. The transducer consists of micro bimorph cantilevers (Aluminum-Silicon) and split ring resonators, operating at millimeter wave frequencies around 30 GHz. As the temperature changes, the bilayer cantilevers deflect and thus alter the resonant frequencies of the resonators. The design achieves a sensitivity of 1.05 GHz/um with respect to cantilever deflection, corresponding to a sensitivity of 150 MHz/oC, three orders of magnitude higher than existing passive wireless temperature sensors. The sensor design has high Q factor, is ultra-compact, easily fabricated and integrated with other passive sensors in sensing networks. Depending on material choices, the proposed design can also be utilized in harsh environments. To demonstrate the proof-of-concept, scaled designs around 4 GHz are presented, utilizing Aluminum-PET (Polyethylene terephthalate) bilayer cantilevers, achieves a sensitivity of 2.14 MHz/oC. WE1D: Advances in microwave sensors and object detection systems.

Advanced Electromagnetic Metamaterials for Temperature Sensing Applications

“…This is because some of the used substrate materials and/or constructed sub-wavelength structures have high temperature sensitive property. According to the sensing mechanism of resonant-type metamaterial-inspired sensors mentioned above, the temperature sensitive dielectric substrate materials and the sub-wavelength nano/micro mechanical structure with thermal expansion coefficient differences will result in the changings of resonant frequency/strength under different temperatures [38][39][40][41][42].…”

“…Based the different thermal expansion coefficients of different substrates used in the metamaterials, the bending deformations due to the changes of background temperature will alter the equivalent capacitance/inductance parameters of the meta-atom, thereby causing the resonant frequency shift or resonance strength change. For examples, Thai et al firstly loaded a cantilever arm at the open slot of the metal SRR as shown in Figure 1A-i [38,50]. The arm consisted of two layers of heterogeneous materials with different thermal expansion coefficients.…”

“…As shown in Figure 1C-i, the absorbing element is connected to two Al/SiOx microcantilevers (legs), anchored to a silicon substrate, which acts as a heat sink, allowed the sensor to return to its undisturbed position when the excitation was stopped. Figure 1C-ii shows the experimental results for the temperature sensing properties, which indicates a sensitivity of 0.2 deg/ • C. [38,50], (B) nanoscale reconfigurable photonic metamaterials and the corresponding temperature changing performances [51], (C) Metamaterial absorber configuration fabricated on a microcantilevers and the accordingly temperature changing inspired structure deformation performance [29].…”

Concept and Model of a Metamaterial-Based Passive Wireless Temperature Sensor for Harsh Environment Applications

“…These applications require that the sensor is easy to fabricate, cheap, small, easy to integrate and highly reliable. However, most existing solutions require a power source or have low temperature limitations [1][2][3]. Optical based wireless sensors were developed but the accuracy was not satisfactory [4,5].…”

“…Cheng et al [10] have developed a resonator/antenna based wireless temperature sensor and reported test results at 1000°C. Thai et al [1] used micro-bimorph cantilevers to develop an ultrasensitive temperature sensor working at a high frequency of 30 GHz. Metamaterials have drawn significant attention lately because of their ability to display extraordinary properties such as negative refractive index, reverse Doppler effect etc.…”