a b s t r a c tMicrofluidic capacitive sensors have been used for detection of droplets, however they have been lacking the sensitivity required for detecting the content of droplets. In this study, we developed a scalable, portable, robust and high sensitivity capacitive microdroplet content detection system using coplanar electrodes with nanometer thick silicon dioxide (SiO 2 ) passivation layer and off-the-shelf capacitive sensors. The microfluidic chip we have designed provides easy and rapid modification of droplet content by mixing two aqueous liquids at any given ratio. The change in dielectric constant of the droplet content leads to the change in capacitive signal. The dielectric content of droplets was modified continuously while corresponding capacitance signal was measured. The resolution of the system was measured as 3 dielectric permittivity units. The results were verified using a semiconductor parameter analyzer. The application specific integrated circuit used in this work enables a portable, low-cost detection system and matches the performance of bench-top analyzers. Automated and precise measurement of dielectric content in droplets for biochemical assay monitoring is a major application of the presented system.

We report a biosensing platform for viral load measurement through electrical sensing of viruses on a flexible plastic microchip with printed electrodes. Point-of-care (POC) viral load measurement is of paramount importance with significant impact on a broad range of applications, including infectious disease diagnostics and treatment monitoring specifically in resource-constrained settings. Here, we present a broadly applicable and inexpensive biosensing technology for accurate quantification of bioagents, including viruses in biological samples, such as plasma and artificial saliva, at clinically relevant concentrations. Our microchip fabrication is simple and mass-producible as we print microelectrodes on flexible plastic substrates using conductive inks. We evaluated the microchip technology by detecting and quantifying multiple Human Immunodeficiency Virus (HIV) subtypes (A, B, C, D, E, G, and panel), Epstein-Barr Virus (EBV), and Kaposi’s Sarcoma-associated Herpes Virus (KSHV) in a fingerprick volume (50 µL) of PBS, plasma, and artificial saliva samples for a broad range of virus concentrations between 102 copies/mL and 107 copies/mL. We have also evaluated the microchip platform with discarded, de-identified HIV-infected patient samples by comparing our microchip viral load measurement results with reverse transcriptase-quantitative polymerase chain reaction (RT-qPCR) as the gold standard method using Bland-Altman Analysis.