Sensitivity Analysis of a Portable Wireless PCB-MEMS Permittivity Sensor Node for Non-Invasive Liquid Recognition

Dielectric characteristics are useful to determine crucial properties of liquids and to differentiate between liquid samples with similar physical characteristics. Liquid recognition has found applications in a broad variety of fields, including healthcare, food science, and quality inspection, among others. This work demonstrates the fabrication, instrumentation, and functionality of a portable wireless sensor node for the permittivity measurement of liquids that require characterization and differentiation. The node incorporates an interdigitated microelectrode array as a transducer and a microcontroller unit with radio communication electronics for data processing and transmission, which enable a wide variety of stand-alone applications. A laser-ablation-based microfabrication technique is applied to fabricate the microelectromechanical systems (MEMS) transducer on a printed circuit board (PCB) substrate. The surface of the transducer is covered with a thin layer of SU-8 polymer by spin coating, which prevents it from direct contact with the Cu electrodes and the liquid sample. This helps to enhance durability, avoid electrode corrosion and contamination of the liquid sample, and to prevent undesirable electrochemical reactions to arise. The transducer’s impedance was modeled as a Randles cell, having resistive and reactive components determined analytically using a square wave as stimuli, and a resistor as a current-to-voltage converter. To characterize the node sensitivity under different conditions, three different transducer designs were fabricated and tested for four different fluids, i.e., air, isopropanol, glycerin, and distilled water—achieving a sensitivity of 1.6965 +/− 0.2028 εr/pF. The use of laser ablation allowed the reduction of the transducer footprint while maintaining its sensitivity within an adequate value for the targeted applications.

Fluorescence NanoParticle Detection in a liquid sample using the Smartphone for Biomedical application

In the present work, a Smartphone-based Fluorescence Nanoparticle Detector (SPF-NPD) was developed. This method is intended for use in the identification of biological agents in biomedical applications. Here, an android application-based algorithm was developed to analyze the fluorescent nanoparticle intensity level in a target sample. The setup consists of an LED light source, an Eppendorf tube holder, and a smartphone to acquire the fluorescent intensity level in the sample to enable the detection of pathogens within few seconds. High-resolution cameras available on recent smartphones have made live detection more accurate and convenient for healthcare applications. The concept of fluorescent nanoparticle detection with a smartphone has led to a portable device and having potential application in healthcare. In this proposed method the intensity level is analyzed with 5 pixels algorithm, the center pixel followed by four immediate neighbours’ pixels which can analyze with minimal sample quantity. Also, the robustness of the developed algorithm was verified with various megapixel camera ranges from 8 MP to 20 MP.

Nanomechanical Molecular Mass Sensing Using Suspended Microchannel Resonators

In this work we study the different phenomena taking place when a hydrostatic pressure is applied in the inner fluid of a suspended microchannel resonator. Additionally to pressure-induced stiffness terms, we have theoretically predicted and experimentally demonstrated that the pressure also induces mass effects which depend on both the applied pressure and the fluid properties. We have used these phenomena to characterize the frequency response of the device as a function of the fluid compressibility and molecular masses of different fluids ranging from liquids to gases. The proposed device in this work can measure the mass density of an unknown liquid sample with a resolution of 0.7 µg/mL and perform gas mixtures characterization by measuring its average molecular mass with a resolution of 0.01 atomic mass units.