X-ray is the workhorse modality of medical imaging. But in the field of microfluidics, this old-school technology is on the cutting edge. French researchers have developed new Kapton microdevices that can stand up to the heat from x-ray beams in microfluidics experiments.
"Microfluidics is now a well-established tool for studying chemical reactions, performing biological assays, and even answering fundamental questions of physics. X-ray techniques offer very powerful measurements for elemental (x-ray scattering) and structural (x-ray diffraction) analysis," wrote Ray Barrett and colleagues in Lab on a Chip, the journal of the Royal Society of Chemistry (March 30, 2006, Vol. 6:1, pp. 494-499).
Barrett is from the European Synchrotron Radiation Facility in Grenoble, France. His co-authors are from the Université Bordeaux in Talence and the Laboratoire du Future in Pessac.
Their invention could be of service in studies that focus on protein crystallization or crystallography, which offers an improved understanding of molecular structures. This information can then be used to design drug treatments for specific human, animal, and plant diseases ("Protein Crystal Growth," NASA).
The researchers tested their microdevice to study shear on soft condensed matter. The latter is a subdiscipline of physics that investigates colloidal suspensions, polymers, and surfactants (soap-like molecules).
For this experiment, they created a Kapton or polymide chip. Polymides are commonly used in microelectronics. The Kapton films of 10 x 10 cm2 and thickness of 75 µm were machined by laser ablation.
A monochromatic x-ray microprobe, at energies that varied between 10-30 KeV, was targeted onto worm-like micelles under shear. "Worm-like micelles consist of very long cylindrical aggregates of self-assembled surfactant molecules that mimic polymer solutions," the authors explained. The micelles were then injected at a controlled rate into the Kapton chip. The energy of the x-ray beam was set to 14 KeV.
According to the results, the group was able to successfully control small and large angle x-ray scattering data by varying the distance between the microdevice and the detector. They were also able to provide full control of the hydrodynamics of the worm-like micelles at small length scales.
"Using this present approach, the structure of complex fluids can be investigated with a high spatial resolution (a few microns) ... and therefore mapping of the structure of the fluid can be performed," they wrote.
Barrett's group stressed that they did not perform an in-depth analysis of the data in this study as it was intended to demonstrate a new technique. Further investigation into the complex behavior of fluids using this method would be the next step.
By Shalmali Pal
AuntMinnie.com staff writer
April 24, 2006
Related Reading
X-ray method improves soft-tissue visualization, April 3, 2006
Radiation experiment demonstrates long-term damage to normal tissue, March 31, 2006
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