Crude oil water-cut sensing with disposable laser ablated and inkjet printed RF microfluidics

This paper presents the first microwave microfluidic crude oil/water cut sensor. Anhydrous crude oil is been tested and the device provides a measurable frequency shift of 500MHz at 50% (vol.) water content and a 50MHz shift for a 5% (vol.) water concentration. The sensor is realized with a low-cost direct write fabrication method. This involves laser ablation, inkjet printing, laser heating, along with low temperature thermal compression bonding of Poly (methylmethacrylate) (PMMA) sheets. By using localized laser sintering a conductivity of 2.5e⁶ S/m is achieved for silver nanoparticle ink without the need to heat the entire substrate above its glass transition temperature of (105 °C). The dielectric properties of PMMA are characterized to 1 GHz and a simulation model is offered for analyzing the dielectric properties of crude oil. This work demonstrates that a small form factor and low cost device is capable of precise water-cut measurements.