A Wearable Electrochemical Platform for Noninvasive Simultaneous Monitoring of Ca2+ and pH

Hnin Yin Yin Nyein, Wei Gao, Ziba Shahpar, Sam Emaminejad, Samyuktha Challa, Kevin Chen, Hossain M. Fahad, Li Chia Tai, Hiroki Ota, Ronald W. Davis, Ali Javey

Research output: Contribution to journalArticlepeer-review

442 Scopus citations


Homeostasis of ionized calcium in biofluids is critical for human biological functions and organ systems. Measurement of ionized calcium for clinical applications is not easily accessible due to its strict procedures and dependence on pH. pH balance in body fluids greatly affects metabolic reactions and biological transport systems. Here, we demonstrate a wearable electrochemical device for continuous monitoring of ionized calcium and pH of body fluids using a disposable and flexible array of Ca2+ and pH sensors that interfaces with a flexible printed circuit board. This platform enables real-time quantitative analysis of these sensing elements in body fluids such as sweat, urine, and tears. Accuracy of Ca2+ concentration and pH measured by the wearable sensors is validated through inductively coupled plasma-mass spectrometry technique and a commercial pH meter, respectively. Our results show that the wearable sensors have high repeatability and selectivity to the target ions. Real-time on-body assessment of sweat is also performed, and our results indicate that calcium concentration increases with decreasing pH. This platform can be used in noninvasive continuous analysis of ionized calcium and pH in body fluids for disease diagnosis such as primary hyperparathyroidism and kidney stones.

Original languageEnglish (US)
Pages (from-to)7216-7224
Number of pages9
JournalACS Nano
Issue number7
StatePublished - Jul 26 2016

All Science Journal Classification (ASJC) codes

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)


  • flexible electronics
  • in situ analysis
  • multiplexed sensing
  • system integration
  • wearable biosensors


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