Samsung Advanced Institute of Technology

Bioelectrical impedance analysis (BIA) is used to analyze the body composition of a human by applying a small amount of alternating current through a human body and measuring the impedance. As the electrode size of a BIA device becomes small, the measurement error of impedance becomes large due to the contact resistance between the electrode and the human skin. Most commercial BIA devices, therefore, utilize electrodes large enough to ignore the effect of contact resistance, i.e. 4ⅹ1400 mm2. We propose a novel method for compensating the contact resistance by performing a 4-point and a 2-point measurement alternately such that body impedance can be accurately estimated even with a considerably smaller size of electrodes (68+128 mm2). Also, we report a wrist-wearable BIA device with single-finger contact measurement and clinical test results at Seoul St. Mary’s Hospital from 203 participants: the correlation coefficient and the standard error of estimate (SEE) of percentage body fat was 0.899 and 3.76％, respectively, when compared with dual-energy X-ray absorptiometry (DEXA), which was found to be above the level of performance of commercial upper-body portable body fat analyzer (Omron HBF-306). Considering the measurement time is only 7 sec, this senor technology would provide a new possibility for a wearable bioelectrical impedance analyzer towards wellness applications.