Droplet-based Biosensing for Lab-on-a-Chip, Open Microfluidics Platforms

Abstract

Low cost, portable sensors can transform health care by bringing easily available diagnostic devices to low and middle income population, particularly in developing countries. Sample preparation, analyte handling and labeling are primary cost concerns for traditional lab-based diagnostic systems. Lab-on-a-chip (LoC) platforms based on droplet-based microfluidics promise to integrate and automate these complex and expensive laboratory procedures onto a single chip; the cost will be further reduced if label-free biosensors could be integrated onto the LoC platforms. Here, we review some recent developments of label-free, droplet-based biosensors, compatible with “open” digital microfluidic systems. These low-cost droplet-based biosensors overcome some of the fundamental limitations of the classical sensors, enabling timely diagnosis. We identify the key challenges that must be addressed to make these sensors commercially viable and summarize a number of promising research directions.

Analyzing Thermal Stability of Cell Membrane of Salmonella Using Time-Multiplexed Impedance Sensing

“…The model allows us to associate effective kinetic parameters of permeabilization in wildtype (WT) and heat-resistant (HR) cells and to demonstrate that the latter have a larger effective activation energy and consequently, a stronger cell envelope. The dropletbased impedance sensor is label-free (i.e., it does not use radioactive isotopes or fluorescent dyes) and can be miniaturized and integrated onto lab-on-a-chip platforms (20)(21)(22). In addition, supported by a physics-based quantitative model for the droplet impedance (23), we are able to tune the working frequency for optimum performance and characterize cells in the growth medium.…”

Microfluidic Devices for Label-Free DNA Detection

“…Droplet-based microfluidics are also an ideal integration platform for applications requiring high-throughput analysis [64]. These systems offer the unique advantages of automated Another multiplexed integrated label-free DNA detection platform was proposed by including two functional modules, i.e., a multiplexed PCR module for amplification of nucleic acid targets, and a multiplexed silicon nanowire (SiNW) module for sequence determination [61].…”

“…The introduction of solid state nanopores also allowed more versatility in their fabrication, enabling variable but controlled diameters and geometries, even in sub-nanometer resolutions. Droplet-based microfluidics are also an ideal integration platform for applications requiring high-throughput analysis [64]. These systems offer the unique advantages of automated compartmentalization of reagents in multiple picoliter volume drops, along with the possibility to perform in a programmable way, multiple combinations of reagents rapidly.…”

Fast Active Merging of Microdroplets in Microfluidic Chambers Driven by Photo-Isomerisation of Azobenzene Based Surfactants

“…Many lab-on-a-chip (LoC) applications have become possible thanks to the ability to control mixing of different droplet contents, which enabled the sequencing of many complex bio-chemical and biological reactions with a high level of control and flexibility over the last decade; see for a review [1][2][3][4][5][6][7]. Hence, among all manipulation schemes allowed by droplet-based microfluidics technology [8][9][10][11][12][13][14][15][16], active merging of microdroplets (AMD) is probably one of the most important. It is generally achieved using a high alternating current (AC) voltage [17], or using a direct current (DC) voltage [18].…”