I. Introduction
The interest in fluidic manipulation and detection in microfluidic systems has grown steadily in past decades thanks to several benefits such as using much less sample volume required, providing higher sensitivity, be applicable for various fluidic applications, and cost-saving. Microfluidic emulsion droplet generation and fluidic flow detection hold great potential for scientific areas and commercial applications such as biology, chemistry, and nanotechnology. Several fundamental methods have been studied and developed for fluidic flow detection, such as optical, ultrasonic, and electrical sensing based on contact and contactless mechanisms [1], [2]. In the electrical method, the conventional fluidic detection technique in which the electrodes directly contact with the fluidic shows several limitations such as the polarization effect, electrochemical erosion, and electrode contamination effect [3]. The capacitively coupled contactless conductivity detection (C4D) structure has been proposed and developed to avoid the problems of direct contact sensing. This technique is a desirable option for its simple fabrication and measurement setup, as well as the miniaturization capability [1], [4]-[6]. The passive wireless sensing technique has emerged as a promising method for various purposes such as sensing, detection, and measurement. This technique can be used combined with the conductivity detection method to measure the conductivity of the solution and detect objects flowing in the fluidic channel [7]-[10]. The LC passive sensor technique uses wireless methods, and hence there is no requirement for direct physical connections between the sensor, data logger, and processor [11]. Besides, with the wireless readout method, the system can be more convenient and suitable for various applications.