Lab on a Chip Blog

In a recent paper in Lab on a Chip, a group of British researchers reported a ‘lab-in-a-briefcase’ for detection and quantification of the prostate cancer biomarker PSA in human serum and whole blood. Their lab-in-a-briefcase is a small container with a set of coated plastic capillaries, a pre-loaded microwell plate with reagents and a film scanner.

The researchers stress that their system is cheap and easy to handle, which would make it very useful for performing diagnostics in low resource areas. In addition, their lab-in-a-briefcase demonstrates the potential for point-of-care tests for prostate cancer, which would allow easy screening by non-experts in a non-clinical setting.

The concept of a lab-in-a-briefcase may have more far-reaching implications, though. Most lab-on-a-chip assays and microfluidic systems are usually developed in the context of interdisciplinary research collaborations. One research department may develop a new system, while another department has the – often unstable – samples that are used to demonstrate proof-of-concept. This complexity means that projects can quickly become logistic nightmares.

Multi-site collaborations make the portability and the standardized format that are found in the lab-in-a-briefcase and related technologies very important. It doesn’t matter if the application domain of a project is physics, biochemistry or biology. Developing a portable, standardized set-up with good documentation, automated analysis and easy read-out can contribute greatly to the success of a multi-disciplinary microfluidic engineering project, because it promotes collaboration and a wider application of the technology early on.

All of this means that the lab-in-a-briefcase is not just a niche product that is only useful for cheap point-of-care diagnostics in low resource areas. It is a design concept that anyone in the realm of microfluidic engineering needs to understand. Perhaps the concept is also applicable to the project you’re currently working on?

Go check it out for yourselves – you can download this paper fro free* for a limited time only!

The Reynolds number, ratio of inertial to viscous forces, is low for most microfluidic platforms and has been approximated to zero to model most microscale fluid flows as linear and time-reversible (Stoke’s flow). Yet Dino Di Carlo’s group at the University of California- Los Angeles, among others, have shown that microfluidic systems in which Reynolds’ number ranges from 1 to 100 exhibit non-negligible inertial effects. These forces lead to separation and ordering of particles within channels by stream line crossing due to effects from the channel geometries (lift forces from the channel wall and velocity profile shear gradient). Inertial lift forces are regulated by the channel dimensions and geometry, particle diameter, and flow rate.^[1]

Experimentally-derived intuitions have guided researchers to use the effects of inertial lift forces to produce high throughput flow cytometers to isolate bacteria from diluted blood samples,^[2] systems capable of probing the deformability of cells to evaluate metastatic potential^{[3, 4]} and platforms combined with Dean flow in curved channels to increase mixing of fluids or spirals to improve separation of particles.^[5] Yet the physical underpinnings guiding these channel designs have been limited.

In this review, Amini and colleagues tackle many of the relationships which are important to create new devices by taking advantage of the unique contribution of inertial forces at the microscale. The behavior of non-Newtonian fluids (i.e., whole blood), the role of particle shape on focusing, particle-particle interactions, and the effect of protrusions along the channel length on flow (pillars, herringbone structures) are also discussed and can open exciting new applications in medical diagnostics, chemical synthesis, manufacturing of materials, and beyond. Inertial microfluidics platforms are en route to commercialization by Johnson & Johnson to sort rare circulating tumor cells from whole blood at 10 million cells per second (CTC-iChip^[6]).

Download the full review for free* for a limited time only!

Inertial microfluidic physics
Hamed Amini, Wonhee Lee and Dino Di Carlo. Lab on a Chip, 2014, 14, 2739-2761.
DOI: 10.1039/C4LC00128A

References:
[1] D. Di Carlo, Lab on a Chip, 2009, 9, 3038-3046.
[2] A. J. Mach and D. Di Carlo, Biotechnol. Bioeng., 2010, 107, 302-311.
[3] J. S. Dudani, et al, Lab on a Chip, 2013, 13, 3728-3734.
[4] S. C. Hur, et al, Lab on a Chip, 2011, 11, 912-920.
[5] J. M. Martel and M. Toner, Scientific Reports, 2013, 3.
[6] E. Ozkumur, et al, Sci. Transl. Med., 2013, 5, 179ra47.

*Access is free through a registered RSC account until 25th August 2014 – click here to register

About the WebWriter

Sasha is a PhD student in bioengineering working with Professor Beth Pruitt’s Microsystems lab at Stanford University. Her research focuses on evaluating relationships between cell geometry, intracellular structure, and force generation (contractility) in heart muscle cells. Outside the lab, Sasha enjoys hiking, kickboxing, and interactive science outreach.