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ENGINEERING
High-speed microfluidic differential manometer for cellular-scale hydrodynamics
Division of Engineering and Applied Sciences, Harvard University, Pierce Hall, Cambridge, MA 02138
Edited by Harden M. McConnell, Stanford University, Stanford, CA, and approved November 8, 2005 (received for review August 17, 2005)
We propose a broadly applicable high-speed microfluidic approach for measuring dynamical pressure-drop variations along a micrometer-sized channel and illustrate the potential of the technique by presenting measurements of the additional pressure drop produced at the scale of individual flowing cells. The influence of drug-modified mechanical properties of the cell membrane is shown. Finally, single hemolysis events during flow are recorded simultaneously with the critical pressure drop for the rupture of the membrane. This scale-independent measurement approach can be applied to any dynamical process or event that changes the hydrodynamic resistance of micro- or nanochannels.
pressure measurement | microcirculation | hemolysis | red blood cell | membrane properties
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: RBC, red blood cell; WBC, white blood cell; PDMS, poly(dimethylsiloxane).
Briefly, a negative mask is placed on a silicon wafer that is spin-coated with a 5-µm-thick layer of photoresist polymer (SU-8) and exposed to UV light. The cross-linked design then is developed to obtain a positive mold, and liquid poly(dimethylsiloxane) (PDMS) (Dow-Corning) is poured over the mold. The PDMS is cured and peeled from the mold, and two inlet holes are punched with custom-prepared 20-gauge needles. The PDMS negative mold is bonded irreversibly to a glass slide to produce the device. The suspension of cells is loaded in a gas-tight syringe (Hamilton) and connected to a compressed air tank through custom adapters. Polyethylene (PE 20) tubes are connected from the syringe needle to the inlet hole of the control channel of the device. A similar setup is used with the dyed solution without the suspension and is connected to the inlet hole of the control channel of the device. Pressure applied to the needles is independently controlled by a regulator (Bellofram, St. Louis, MO) with a precision of 0.001 psi (1 psi = 6.89 kPa).
* To whom correspondence should be addressed. E-mail: has{at}deas.harvard.edu.
© 2006 by The National Academy of Sciences of the USA
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