Handheld device adapted to smartphone cameras for the measurement of sodium ion concentrations at saliva-relevant levels via fluorescence

Michelle Lipowicz, Antonio Garcia

Research output: Contribution to journalArticle

2 Scopus citations


The use of saliva sampling as a minimally-invasive means for drug testing and monitoring physiology is a subject of great interest to researchers and clinicians. This study describes a new optical method based on non-axially symmetric focusing of light using an oblate spheroid sample chamber. The device is simple, lightweight, low cost and is easily attached to several different brands/models of smartphones (Apple, Samsung, HTC and Nokia) for the measurement of sodium ion levels at physiologically-relevant saliva concentrations. The sample and fluorescent reagent solutions are placed in a specially-designed, lightweight device that excludes ambient light and concentrates 470-nm excitation light, from a low-power photodiode, within the sample through non-axially-symmetric refraction. The study found that smartphone cameras and post-image processing quantitated sodium ion concentration in water over the range of 0.5–10 mM, yielding best-fit regressions of the data that agree well with a data regression of microplate luminometer results. The data suggest that fluorescence can be used for the measurement of salivary sodium ion concentrations in low-resource or point-of-care settings. With further fluorescent assay testing, the device may find application in a variety of enzymatic or chemical assays.

Original languageEnglish (US)
Pages (from-to)122-138
Number of pages17
Issue number2
StatePublished - Jun 1 2015



  • Fluorescence
  • Low-resource settings
  • Non-axially-symmetric focusing
  • Oblate spheroid
  • Saliva
  • Smartphone
  • Sodium ions

ASJC Scopus subject areas

  • Bioengineering

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