title: Cellphone camera imaging of a periodically patterned chip as a potential method for point-of-care diagnostics.
abstract: In this study, we demonstrate that a disposable chip periodically patterned with suitable ligands, an ordinary cellphone camera, and a simple pattern recognition software, can potentially be used for quantitative diagnostics. A key factor in this demonstration is the design of a calibration grid around the chip that, through a contrast transfer process, enables reliable analysis of the images collected under variable ambient lighting conditions. After exposure to a dispersion of amine terminated silica beads used as analyte mimicking pathogens, an epoxy-terminated glass substrate microcontact printed with octadecyltrichlorosilane (250 μm periodicity) developed a characteristic pattern of beads which could be easily imaged with a cellphone camera of 3.2 MP pixels. A simple pattern recognition algorithm using fast Fourier transform produced a quantitative estimate of the analyte concentration present in the test solution. In this method importantly, neither the chip fabrication process nor the fill-factor of the periodic pattern need be perfect to arrive at a conclusive diagnosis. The method suggests a viable platform that may potentially find use in fault-tolerant and robust point-of-care diagnostic applications.
authors.affiliation: Chemistry and Physics of Materials Unit, DST Unit on Nanoscience, Jawaharlal Nehru Centre for Advanced Scientific Research , Jakkur P.O., Bangalore, Karnataka 560064, India.
authors.forename: Ritu
authors.initials: R
authors.lastname: Gupta
authors.forename: Ronald G
authors.initials: RG
authors.lastname: Reifenberger
authors.forename: Giridhar U
authors.initials: GU
authors.lastname: Kulkarni
mesh_terms: D000465:Algorithms; D040421:Cell Phone; D003952:Diagnostic Imaging / Q000295:instrumentation / Q000379:methods*; D006801:Humans; D019095:Point-of-Care Systems