A Zero-Power Ubiquitous Wireless Liquid-Level Sensor Based on Microfluidic-Integrated Microstrip Antenna

Abstract

Harmonic transponder sensors, receiving radiofrequency (RF) signal and converting it to a modulated second harmonic, have been demonstrated to be effective for signal interrogation in environments with strong clutters. Here, we propose a compact dual-resonance microstrip antenna consisting of an elliptical patch loaded with shorting pins. Such an antenna utilizes the TM e110 resonant mode to intercept the perpendicularly-polarized fundamental tone (2.86 GHz) and uses the TM o110 resonant mode to retransmits the parallelly-polarized second harmonic (5.72 GHz). Moreover, we have developed a harmonic-based wireless liquid sensor comprising the proposed antenna and a micromachined liquid channel. Our measurement results show that even in the noisy environment, the second harmonic strength can precisely indicate the dielectric property of liquid filled in the microfluidic tank (e.g., acetone-water mixtures with various concentrations). However, a similar setup without frequency and polarization modulations (i.e., linear and passive backscatter tag) fails to provide a sensitive and quantitative measurement of liquid property. The proposed low-profile dual-resonance antenna with sensing capability will pave the way for the development of harmonic sensors and nonlinear radio-frequency identification (RFID) tags.

Nanosilver Inkjet-Printed CPW-Fed Flexible Antenna Sensor for Contactless Liquid Acetone/Water Detection

“…10(e) and Fig. 10(f), the response of the sensor to changes in the volume fraction shows a non-linear trend, a characteristic commonly observed in microwave sensors as shown by previous research studies presented in [71], [108], [114], [115]. In addition to presenting this relationship curve, we incorporated error bars in Figs.…”

“…To enhance simulation accuracy and measurement consistency, employing a high-quality, low-loss tangent substrate material is recommended [92]. Implementing these measures will likely minimise disparities, improving the accuracy of the antenna's performance characterisation in both simulation and measurement scenarios.…”

Impacts of Liquid Level on Microwave Resonance Sensing with a Flexible Microfluidic Channel

“…[7,14] Both wireless and wired radio-frequency (RF) liquid sensors have been widely investigated. The wireless RF liquid sensors [15][16][17][18] are used for contactless and long-range measurements, but they are susceptible to the spatial electromagnetic wave interferences. The wired RF liquid sensors are more immune to the spatial electromagnetic interferences, [19,20] and more suitable for compact sensing systems.…”

Absolute value wireless sensing based on nonlinear harmonic analysis assisted with frequency-hopping spread spectrum

“…Inspired by 'harmonic radar' systems capable of tracking low-RCS objects [20][21][22][23], the proposed 'harmonic sensor' system shown in figure 1(a) has a reader that transmits a CW RF signal at frequency f i to the tag, while receives a modulated RF signal at frequency 2f i ; such a frequency orthogonality can effectively prevent noises caused by background clutters and the transceiver (T x )-receiver (R x ) crosstalks on the reader side [24][25][26]. Further, we apply the frequency-hopping spread spectrum (FHSS) method to enable the absolute value sensing [27,28].…”