LiFT (a Lithium Fiber‐based Test): An At‐home Companion Diagnostics for a Safer Lithium Therapy in Bipolar Disorder

Abstract This work presents LiFT (a lithium fiber‐based test), a low‐cost electrochemical sensor that can measure lithium in human saliva and urine with FDA‐required accuracy. Lithium is used for the treatment of bipolar disorder, and has a narrow therapeutic window. Close monitoring of lithium concentration in biofluids and adjustment of drug dosage can minimize the devastating side effects. LiFT is an inexpensive, yet accurate and simple‐to‐operate lithium sensor for frequent at‐home testing for early identification of lithium toxicity. The low cost and high accuracy of LiFT are enabled through an innovative design and the use of ubiquitous materials such as yarn and carbon black for fabrication. LiFT measures Li + through potentiometric recognition using a lithium selective sensing membrane that is deposited on the ink‐coated yarn. A detection limit of 0.97 µM is obtained with a sensitivity of 59.07±1.25 mV/decade for the Li + sensor in deionized water. Moreover, the sodium correction extended LiFT's linear range in urine and saliva to 0.5 mM. The LiFT platform sends the test results to the patient's smartphone, which subsequently can be shared with the patient's healthcare provider to expedite diagnosis and prevention of acute lithium toxicity.