Microfluidic Tool Box as Technology Platform for Hand-Held Diagnostics

• Published in: Clinical chemistry (Baltimore, Md.) Md.), 2005-10, Vol.51 (10), p.1923-1932
• Main Authors: Pugia, Michael J, Blankenstein, Gert, Peters, Ralf-Peter, Profitt, James A, Kadel, Klaus, Willms, Thomas, Sommer, Ronald, Kuo, Hai Hang, Schulman, Lloyd S
• Format: Article
• Language: English
• Subjects: Ablation; Analytical, structural and metabolic biochemistry; Biological and medical sciences; Blood; Blood Glucose - analysis; Blood vessels; Chemistry; Chromatography; Contact angle; Equipment Design; Fundamental and applied biological sciences. Psychology; Glucose; Glycated Hemoglobin A - analysis; Hemoglobin; Humans; Humidity; Immunoassay; Immunoassay - instrumentation; Injection molding; Inlets; Investigative techniques, diagnostic techniques (general aspects); Lasers; Medical sciences; Microelectromechanical systems; Microfluidic Analytical Techniques - instrumentation; Microfluidic Analytical Techniques - methods; Microfluidics - instrumentation; Microfluidics - methods; Point of care testing; Point-of-Care Systems; Reagents; Sensitivity and Specificity; Surface Properties; Urinalysis; Urinalysis - instrumentation
• ISSN: 0009-9147; 1530-8561
• DOI: 10.1373/clinchem.2005.052498

Use of microfluidics in point-of-care testing (POCT) will require on-board fluidics, self-contained reagents, and multistep reactions, all at a low cost. Disposable microchips were studied as a potential POCT platform. Micron-sized structures and capillaries were embedded in disposable plastics with mechanisms for fluidic control, metering, specimen application, separation, and mixing of nanoliter to microliter volumes. Designs allowed dry reagents to be on separate substrates and liquid reagents to be added. Control of surface energy to +/-5 dyne/cm2 and mechanical tolerances to < or = 1 microm were used to control flow propulsion into adsorptive, chromatographic, and capillary zones. Fluidic mechanisms were combined into working examples for urinalysis, blood glucose, and hemoglobin A(1c) testing using indicators (substances that react with analyte, such as dyes, enzyme substrates, and diazonium salts), catalytic reactions, and antibodies as recognition components. Optical signal generation characterized fluid flow and allowed detection. We produced chips that included capillary geometries from 10 to 200 microm with geometries for stopping and starting the flow of blood, urine, or buffer; vented chambers for metering and splitting 100 nL to 30 microL; specimen inlets for bubble-free specimen entry and containment; capillary manifolds for mixing; microstructure interfaces for homogeneous transfer into separation membranes; miniaturized containers for liquid storage and release; and moisture vapor barrier seals for easy use. Serum was separated from whole blood in