Colorimetric microchip assay using our own whole blood collected by a painless needle for home medical care

We have developed a colorimetric measurement chip that measures triglycerides, total cholesterol, and high-density lipoprotein in 6 μL of whole blood collected with a painless needle. The chip can be used by patients to self-monitor certain health conditions at home. This chip contains a sharp 150 μm diameter stainless steel (SUS) needle that collects blood painlessly. The chip consists of three layers of injection-molded poly(methyl methacrylate) bonded together with two double-sided tapes. Two commercial reagents are used, and the volume ratio of plasma to reagent is doubled from the reagent specification to reduce the optical absorption length (and chip mass) by half. Centrifugal force separates the plasma from the blood, and then weighs out and mixes the plasma and reagents. A zigzag channel allows mixing of the plasma with the reagents mainly by vortex motion due to the centrifugal force generated at the corners of the channel. The measured values correlated well with conventionally tested values.