Two-Dimensional Array Sinusoidal Waves Conductor for Biometric Measurements

Goal: For personalized clinical applications, flexible conductors require both high electrical conductivity and resistance to stretching and bending. Here, we developed a two-dimensional array sinusoidal wave (TDAS) conductor, characterized its electrical properties under stretching and bending loads, and measured photoelectric pulse waves. Methods: TDAS structures with wavelengths of 500-2000 μm and amplitudes of 50-200 μm were microfabricated on Al substrates. These structures were then transferred to dimethylpolysiloxane, followed by Au sputtering to obtain TDAS conductors. Results: TDAS conductors with a 200-μm amplitude suppressed the increase in resistance to stretching and bending and maintained conductivity >30% stretching. The small cracks in the valleys observed with electron microscopy contributed to its stretching properties. The connection of LEDs and photodiodes to the TDAS conductors enabled fingertip pulse wave detection. Conclusions: Film-type TDAS conductors, which can maintain high conductivity during stretching and bending, have potential for stress-free physiological monitoring of organs such as the heart as well as the body surface.