Stretchable, Patch‐Type Calorie‐Expenditure Measurement Device Based on Pop‐Up Shaped Nanoscale Crack‐Based Sensor

Demands for precise health information tracking techniques are increasing, especially for daily dietry requirements to prevent obesity, diabetes, etc. Many commercially available sensors that detect dynamic motions of the body lack accuracy, while novel strain sensors at the research level mostly lack the capability to analyze measurements in real life conditions. Here, a stretchable, patch‐type calorie expenditure measurement system is demonstrated that integrates an ultrasensitive crack‐based strain sensor and Bluetooth‐enabled wireless communication circuit to offer both accurate measurements and practical diagnosis of motion. The crack‐based strain gauge transformed into a pop‐up‐shaped structure provides reliable measurements and broad range of strain (≈100%). Combined with the stretchable analysis circuit, the skin attachable tool translates variation of the knee flexion angle into calorie expenditure amount, using relative resistance change (R/R0) data from the flexible sensor. As signals from the knee joint angular movement translates velocity and walking/running behavior, the total amount of calorie expenditure is accurately analyzed. Finally, theoretical, experimental, and simulation analysis of signal stability, dynamic noises, and calorie expenditure calculation obtained from the device during exercise are demonstrated. For further applications, the devices are expected to be used in broader range of dynamic motion of the body for diagnosis of abnormalities and for rehabilitation. A patch‐type calorie expenditure measurement system that utilizes the nanoscale crack‐based strain gauge sensor, along with a wireless Bluetooth module in a stretchable fully integrated circuit format is presented. The device is capable of sensing and analyzing dynamic motions of the knee joint via wireless signals transferring to a portable system.