FMN Lab microfluidic technologies in Elveflow review material
One of the largest European manufacturers in the field of microfluidics, Elveflow, devoted a review material to on-chip automatic efficient bacteria separation and preconcentration method with the use of pressure-driven flow-controlled microfluidics developed by a team of researchers from the Bauman Moscow State Technical University and the Institute of Biochemical Physics, Russian Academy of Sciences.
The proposed approach implies microfiltration of particles of different sizes on a multilayer microfluidic chip with built-in membrane valves. The on-chip automatic sorting sequence consisted of four steps: filling chip with buffer, a sample filtration, dead volume washout and retentate backflush in reverse flow. This work has shown that pulse backflush mode and volume control can dramatically increase microparticles sorting and preconcentration efficiency. The microfluidic chip had two input inlets for supplying the sample and the buffer, six integrated membrane valves (<100 nL dead volume), hydrophilic PVDF filter with 0.45 μm pore diameter, six pneumatic valve control lines and three outlets for filtrate, retentate and waste. The team used multilayer soft lithography technology to fabricate the chip from fully biocompatible materials.
The experimental separation setup consisted of a control PC, a microfluidic flow controller OB1 MK3+ pneumatic valves controller (Elveflow, France), an image capture system based on a high-speed Pixelink camera (Navitar, USA), a Nikon SMZ800N microscope, the home-made stage holder and reservoirs for inflow and outflow liquids.
During the experiments, the valves actuation and the supply of liquids to the chip occurred automatically according to a previously created algorithm in the developed homemade software package. The real-time valves control was carried out using the image capture system.
A scalable microfluidic solution for batch micro- and nanoparticle separation based on microfiltration principle and robust on-chip valve flow control was introduced. The team demonstrated a novel implementation of batch filtration method for on-chip automated separation and preconcentration of 1 mL colloid solution of E.coli bacteria cells.
The developed method allows micro- and nanoparticles separation from sub-mL liquid samples using automatic on-chip cyclic operations— at the end of each cycle, the microfluidic system gets back to the initial state and ready to separate the next sample portion.
Due to such an approach, both filtrate (nanoparticles) and retentate (bacteria) are available in the system’s output channels for subsequent processing or analysis. The great scaling potential of on-chip platforms allows several microfluidic chips with purposefully chosen filters to be sequentially connected for two or more dissimilar sized particles separation and preconcentration.
With the help of pressure-driven flow controlled microfluidics, the presented platform performs a basic yet essential operation, which makes it highly application-flexible and scalable. For more information about what the authors have achieved, please refer to the original paper published in Scientific Reports, available here.
Scheme (a) and photography (b) of the experimental setup
Engineered and assembled with different microfluidic modules for sequent steps of sample preparation, chemical reactions and analyte detection, the results of this work will serve as a stepping-stone for the development of future cost-effective fully automated point-of-care devices.