Bio

Aida Ebrahimi received her BSc and MSc degrees both in Electrical and Computer Engineering from University of Tehran, Iran. Her Master’s project was on fabrication and characterization of highly sensitive capacitive sensors and actuators based on Branched Carbon Nanotubes (BCNTs). In 2012, she joined CEED group, under supervision of Prof. M. A. Alam at Purdue University, West Lafayette, IN, USA. She is currently pursuing a PhD degree in ECE. The title of her dissertation is ‘Droplet-based non-Faradaic Impedance Sensing for Combating Antibiotic Resistance’.
During her academic life, Aida has developed the required skills to approach scientific problems. She has been involved in various, yet connected, projects whose outcome has been published in 15 peer-reviewed journal articles and more than 10 conference proceedings. She enjoys diversity in scientific thinking and intertwining various disciplines to advance the state of the art of a specific problem, especially in health-related applications. Aida is a recipient of Meissner Fellowship Award (Purdue University, 2011) and Bilsland Dissertation Fellowship Award (Purdue University, 2015).

Droplet-based impedance spectroscopy for highly-sensitive biosensing within minutes

Droplet-based impedance spectroscopy for highly-sensitive biosensing within minutes

Rapid detection of biomolecules in small volumes of highly diluted solutions is of essential interest in various applications, such as food safety, homeland security, fast drug screening, and addressing the global issue of antibiotic resistance. Toward this goal, we developed a label-free, electrical approach which is based on (i) evaporation-induced beating of diffusion limit for reducing the sensor response time and (ii) continuous monitoring of non-Faradic impedance of an evaporating droplet containing the analytes.
Small droplets are deposited and pinned on a multifunctional, specially designed superhydrophobic sensor which results in highly-controlled evaporation rate, essential for highly-precise data acquisition. Our method is based on the change of the droplet’s impedance due to ionic modulation caused by evaporation. The time-multiplexing feature of the developed platform results in a remarkably reduced data variation, which is necessary for a reliable biosensing assay.
Furthermore, we examined applicability of the developed technique as a fast, label-free platform for: improving the detection limit of classical methods by five orders of magnitude (detection of attomolar concentration of biomolecules), selective identification of DNA hybridization (down to nM concentration, without any probe immobilization), and bacterial viability (detection is achieved within minutes, as opposed to hours in conventional methods). More specifically, the proposed viability assay relies on a basis fundamentally different from most bacterial viability assays which rely on cell multiplication. Instead, our method is based on modulation of the osmotic pressure to trigger cells to modify their surroundings.

The developed paradigm eliminates the need for bulky reference electrodes (which impose integration challenges), requires only a few microliter sample volume, and is cost-effective and integrable with the microfabrication processes. It has therefore the potential for integration in portable, array-formatted, point-of-care applications.