Micronics Patents H-Filter, Associated Technology
Microfluidics is the Key
How the H-Filter Works
The University of Washington has been awarded US Patent 5,971,158 for microfiltration technology licensed to Micronics Inc. (Redmond, WA). The patent, "Absorption-Enhanced Differential Extraction Device," covers key technologies that Micronics is commercializing as the company's H-Filter brand of blood filters. H-Filters, together with Micronics' T-Sensors, form a novel microfluidic system that miniaturizes analytical chemical and medical diagnostic instrumentation. Together, H-Filter and T-Sensor allow measurement of a wide variety of blood components directly in whole blood without centrifugation or blood cell removal.
The new patent also covers a simple extraction procedure for chemical components from microsamples, with many applications in chemical and biochemical analysis. Micronics believes that eventually H-Filter/T-Sensor devices will make assays faster and easier to run—a boon for analysis of hazardous materials by junior-level technicians. In addition to analytical instruments, Micronics hopes to commercialize its microanalyzers through a line of portable medical sensors/analyzers for home care, physician offices, and emergency medicine.
Microfluidics is the Key (Back to Top)
Micronics' technology is based on microfluidics—the special behavior of fluids flowing in channels the size of a human hair. Fluids in this environment show very different properties than in the macro world of pipes, tubes, and even mm-sized capillaries. Microfluidics, in turn, is enabled by advances in microfabrication—etching silicon to create very small features. Most early microfluidic devices (and many today) are made from silicon because, as industry experts will tell you, very flat, high-quality silicon is cheaper—thanks to the microelectronics revolution—than glass or plastic with similar physical characteristics. In addition to the economic material of choice, silicon microdevices may sometimes be integrated with silicon-based electronics to produce a truly integrated, matchbook-sized instrument. Lab-on-a-chip practicality—and miniaturization—is limited therefore by the need to inject samples, read data, and control the instrument.
Several lab-on-a-chip companies, including Micronics, are beginning to use plastic devices that can be molded instead of etched. Plastic analyzers will eventually be combined as building blocks to construct larger instruments. When these devices hit the marketplace point of care and research tests will be delivered at a cost of pennies per test to the test supplier—don't hold your breath for any medical test that costs "pennies."
Micronics' microfluidic technology is based on research done initially at the University of Washington in the departments of Bioengineering, Electrical Engineering, Mechanical Engineering, and Laboratory Medicine. The university licensed the patents and technology resulting from this research exclusively to Micronics.
How the H-Filter Works (Back to Top)
Micronics' H-Filter continuously separates particles by size, e.g. the separation of blood cells from plasma. H-Filters were named for the resemblance of their microfabricated fluidic channels to the letter ‘H' (see figure).
H-Filter—Microseparator/extractor
H-Filters rely on the absence of turbulent mixing within a microfluidic channel at low Reynold's numbers. Two flow streams can be brought together and run side by side in the center channel of the ‘H' with laminar flow characteristics. Because there is no mixing, the only transport of molecules from one stream to the other is by diffusion.
Diffusion is basically the movement of particles from areas of high concentration to areas of lower concentration. Diffusion is a natural phenomenon, requiring no external source of energy. The major factors affecting the rate of diffusion are (a) the size of the particles; (b) the viscosity of the solution; and (c) the temperature of the medium.
In the figure above, small molecules diffuse quickly from a sample stream to the buffer stream, while very large molecules and particles will remain indefinitely in the sample stream because of their much larger size and much decreased diffusion rate. The H-Filter, therefore, has the capability of separating and isolating components of a sample without the need for centrifugation or filtration. There is no equipment involved, except the fluid pumps, and no physical filter which would clog and require replacement. This technology has been applied to a variety of fluids including human blood, to separate and isolate components.
The H-Filter has application in the areas of sample processing for analytical chemistry, and rare reagent isolation and recovery—activities of prime importance to the biopharmaceutical industry. Micronics plans to use this technology as a front end to medical diagnostics.
Micronics is seeking to out-license this technology for non-diagnostic applications.
For more information: Bernhard H. Weigl, Business Development Manager, Micronics Inc., 8717 148th Ave. NE, Redmond, WA 98052. Tel: 425-895-9197, ext. 15. Fax: 425-895-1183.
By Angelo DePalma