Table 2.

Summary of recent smartphone spectroscopy systems.

Detection Target	Methodology	Materials	LoD/Performance	Smartphone Use	Reference
Microbial spoilage on beef	Mie scattering	Positioning stages, 880 nm NIR LED	101 CFU mL−1 to 108 CFU mL−1	Built-in gyro sensor and camera spectroscopy	[32]
Generic application	Spectroscopic colorimetry	3D printed housing, LED array, Phidgets board, and VIS-spectrometer	Good agreement to certified spectra with dE/E ranging from 0.5% to 1.5%	IoT device to be used with smartphone	[33]
Glucose and ethanol in alcoholic beverages	FTIR spectroscopy and independent component analysis	Graphite light source, ATR prisms, 2-dimensional light receiving device for smartphone	Wavelength resolution 0.057 μm	Proposed as a bean-size spectroscopic module to be mounted on smartphones	[34]
ChlF detection in a variety of apple samples	UV fluorescence spectroscopy	UV LED, nozzle-like enclosure VIS-spectrometer, Arduino pro mini µ, Bluetooth	Satisfactory agreement observed between ripeness and fluorescence signals	Dedicated app interface on smartphone to communicate, receive, plot, and analyse spectral data	[35]
E. coli contamination on meat	Fluorescence-based imaging	4405-nm 10 W LEDs, CCD camera, optical filter at 670 nm, and Wi-Fi transmitter	Localization of most fecal contamination spots successfully identified	Outlined real-time broadcasting to monitoring device such as smartphone	[36]
Generic food sensing application	Hyper-spectral imaging	Tunable MEMS FPI, Bluetooth	Operation range 450–550 nm with spectral resolution 8–15 nm @FWHM	Mobile phone-compatible hyper-spectral imager	[37]
Food quality testing	Diffractive interference refractometry	5 mW semiconductor red laser, circular spatial filter, Si detectors, and a PDMS device	LoD of 4 × 10−4 RIU	Outlined smartphone interface based on transmission mode configuration	[38]
Sugar content prediction in pears	NIR spectrometry and PLS	4 tungsten lamps, LVF 620–1080 nm and CMOS linear detector array	Low power, SNR ratio up to 5000, R2 0.96, SEC 0.29° Bx and SEP 0.46° Bx	Instrument wirelessly operated with smartphone	[39]