A novel lab-on-a-chip design by sequential capillary–gravitational valves for urinary creatinine detection

Abstract

For the first time, instead of the high centrifugal acceleration (or force) by high speed rotation as the driving source that commonly used in the literature, a novel design of capillary–gravitational valves has been developed in a disposable plastic chip by simple control of the balance between capillary and gravitation forces for sequential functions of fluid material delivery, metering and mixing with much less needed power in this study. An integrated lab-on-a-chip (LOC) module with full functions from the sampling to detection for the urinary creatinine measurement has been further tested and verified its use by simply adjusting the LOC tilt angle. The sequential operation can be even operated by hand in the cases of unstable electricity or for regions without AC electric power. Furthermore, the concentration of urinary creatinine was measured by the transmitting optical density (O.D.) change for a Jaffe reaction and calibrated with the coefficient of variations (CV) less than 3.5%. Real urine samples were also tested and showed highly consistent in compare with clinical method.