A triple-layer microchannel array chip with micro through-holes for smartphone based point-of-care testing of biomarker

Colorimetric detection on a microchip frequently suffers the sensitivity problem due to the limited optical path length. Herein, a point-of-care testing (POCT) device based on the colorimetric detection on a microchip with an array of micro through holes for enlarged optical length and an optical imaging system was demonstrated. Each micro through hole has a depth of 2 mm and a volume roughly 0.6 ill, connecting to a microchannel for the efficient reaction. Up to 32 micro through holes were arranged compactly along a round region with a diameter of 13 mm to make them effectively captured by a smartphone camera in a short distance (6.5 cm). For reliable smartphone imaging, a handheld, battery powered optical imaging cassette was made by three-dimensional (3D) printing. A data processing program was also written to realize the detection area selection, RGB (red, green, blue) value reading and detection signal calculation. With the integrated device, a biomarker, human immunodeficiency virus (HIV) p24 antigen in human serum was detected down to 20 pg/ml, much better than that with microchannels. The proposed microchip and the imaging system can be a promising POCT or on-site detection tool based on colorimetric detection.

Automated summary

This article introduces a portable testing device based on colorimetric detection on microchips with an array of micro through holes for increased optical length and an optical imaging system. The device can be used for reliable imaging with smartphones and can detect very low concentrations of biomarkers.