Integrated spectroscopic analysis system with low vertical height for measuring liquid or solid assays

We describe the design, fabrication, and demonstration of a compact spectroscopic analysis system that utilizes a linear variable filter chip attached directly over an image sensor array, and an integrated broadband LED illuminator that supplies light from the edge of the system to provide a low vertical dimension. The instrument is capable of accurately measuring the optical absorption spectra of colored liquids or the scattered spectra from solid objects that are placed in the illumination pathway. Due to the small vertical thickness of the system, the low cost of its components, and the accuracy with which it renders spectra in comparison to conventional spectrometers, we envision potential incorporation of the system into mobile communication devices, such as smartphones and tablets, as a means for providing a dedicated sensor for health diagnostic, environmental monitoring, and general-purpose color sensing applications. As representative examples, the system is demonstrated for quantitatively measuring the liquids of a fetal fibronectin enzyme linked immunosorbent assay (ELISA) and for differentiating the color of pH test strips. A 3D-printed microfluidic cartridge comprised of a linear array of liquid compartments is demonstrated as a simple means for interfacing with the system, and for performing multiple measurements in series that can easily include experimental controls, concentration standards, and replicates.