Bharath Babu Nunna1, Debdyuti Mandal1, Joo Un Lee2, Harsimranjit Singh1, Shiqiang Zhuang1, Durgamadhab Misra3, Md Nasir Uddin Bhuyian3 and Eon Soo Lee1*

Nunna et al. Nano Convergence (2019)



Integrating microfluidics with biosensors is of great research interest with the increasing trend of lab-on-the chip and

point-of-care devices. Though there have been numerous studies performed relating microfluidics to the biosensing

mechanisms, the study of the sensitivity variation due to microfluidic flow is very much limited. In this paper, the sensitivity

of interdigitated electrodes was evaluated at the static drop condition and the microfluidic flow condition. In

addition, this study demonstrates the use of gold nanoparticles to enhance the sensor signal response and provides

experimental results of the capacitance difference during cancer antigen-125 (CA-125) antigen–antibody conjugation

at multiple concentrations of CA-125 antigens. The experimental results also provide evidence of disease-specific

detection of CA-125 antigen at multiple concentrations with the increase in capacitive signal response proportional

to the concentration of the CA-125 antigens. The capacitive signal response of antigen–antibody conjugation on

interdigitate electrodes has been enhanced by approximately 2.8 times (from 260.80 to 736.33 pF at 20 kHz frequency)

in static drop condition and approximately 2.5 times (from 205.85 to 518.48 pF at 20 kHz frequency) in

microfluidic flow condition with gold nanoparticle-coating. The capacitive signal response is observed to decrease at

microfluidic flow condition at both plain interdigitated electrodes (from 260.80 to 205.85 pF at 20 kHz frequency) and

gold nano particle coated interdigitated electrodes (from 736.33 to 518.48 pF at 20 kHz frequency), due to the strong

shear effect compared to static drop condition. However, the microfluidic channel in the biosensor has the potential

to increase the signal to noise ratio due to plasma separation from the whole blood and lead to the increase concentration

of the biomarkers in the blood volume for sensing.


Keywords: Biosensor, Interdigitated gold electrodes, Microfluidic channel, Gold nanoparticles, Capacitance