Fig. 3: Design and validation of the SPOT device.

a Rendering of the fully enclosed SPOT device along with a partially exploded view. Users press buttons to power on the device (1) and start detection reactions (2) and read results on the integrated LCD screen (3). Reaction progress is displayed on the LCD screen and indicator LEDs (4). The SPOT device can export data via a USB cable (5) and be recharged. An electronics cap covers the optical and thermal modules, which are comprised of a capillary in a copper heat block, a cooling fan, a photodiode PCB placed securely behind emission bandpass filters, a structural platform, and an excitation bandpass filter covering a 470 nm excitation LED and PCB. The reaction timings, temperature, and results interpretation are performed on a main circuit board powered by a rechargeable battery, contained within a main enclosure capped with front and back covers. b, c Capability of performing detection by using the SPOT device. SPOT assays using γ-irradiated virus spiked samples were run on both the SPOT device (green dots for N gene in b and red dots for E gene in c) and a thermocycler (gray dots in b and c), then fluorescence values were measured on the SPOT device. SPOT assays performed on the SPOT device using γ-irradiated virus spiked samples at 0, 43.8, 175, and 1750 viral copies per reaction (n = 3). d Validation using clinical saliva samples in a blinded test. Patient sample fluorescence data from SPOT device readout. Clinical samples from 104 patients were collected from the campus of University of Illinois at Urbana-Champaign. Signal intensities from SPOT were measured using a ×2 amplifier gain on photodiode signal, with a positive threshold set at 5× s.d. above background. “PC” indicates the positive control sample, “NC” indicates the negative control sample. Source data are provided as a Source Data file.