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

We present the design and development of a combined octagonal and square-shaped coplanar waveguide (CPW)-fed nanosilver inkjet-printed Kapton polyimide-based flexible antenna sensor for liquid acetone/water detection which is the first of its kind. Sensing was performed by monitoring the resonant frequency and its corresponding amplitude of the reflection coefficient. Our experimental results show that the antenna sensor can distinguish between water and acetone, and it can also respond to varying concentration levels of acetone. The overall size of the antenna sensor is
$0.564\lambda _{{0}} \times 0.627\lambda _{{0}} \times 0.001175\lambda _{{0}}$
, where
$\lambda _{{0}}$
is calculated at 4.7 GHz. The proposed sensor can operate under deformed conditions, making it suitable for sensing near a liquid mixture (acetone–water) by wrapping around the sample holder surface. The results without materials under test show a 10-dB impedance bandwidth between 4.61 and 4.81 GHz in simulations and from 4.42 to 4.86 GHz in measurements. The simulation results also show a peak realized gain of 4.44 dBi with a maximum total efficiency of 92.8%. In comparison, the measured gain of 4.12 dBi at 4.7 GHz with a maximum total efficiency of 76.5%. Furthermore, experimental results considering the materials under test show that the resonant frequency of the sensor was at 4.63 and 4.54 GHz without and with 100% acetone presence in liquid mixtures, respectively. Thus, the proposed antenna sensor has great potential in noncontact liquid acetone sensing applications, paving the way for antenna-based liquid sensing solutions.