Hydrogel-Fractal Piezoelectric Bilayer Transducer for Wireless Biochemical Sensing

• Main Authors: Islam, Sayemul, Park, Moonchul, Song, Seung Hyun, Kim, Albert
• Format: Conference Proceeding
• Language: English
• Subjects: fractal; hydrogel; ultrasound transducer
• ISSN: 1558-4615; 2694-0604
• DOI: 10.1109/EMBC44109.2020.9175819

This paper reports on a novel transducer for wireless biochemical sensing. The bilayer transducer consists of a fractal piezoelectric membrane and pH-sensitive chemo-mechanical hydrogel, which overcomes many shortcomings in the chemical and biochemical sensing. The fractal design on the piezoelectric membrane enhances frequency response and linearity by employing periodically repeated pore architecture. As a basis of the pore, a Hilbert space-filling curve with modifications is used. On the surface of the fractal piezoelectric membrane, the hydrogel is laminated. When the bilayer transducer is introduced to a pH environment (e.g., pH = 4, 8, and 12), the hydrogel swells (or shrinks) and induces the curling of the bilayer transducer (10.47°/pH). The curvature then exhibits various ultrasound responses when the bilayer transducer was excited. The measured voltage outputs using an ultrasonic receiver were 0.393, 0.341, 0.250 mV/cm 2 when curvature angles were 30°, 60°, and 120°, respectively. Overall pH sensitivity was 0.017 mV/cm 2 /pH. Ultimately, the biochemical sensing principle using a novel bilayer ultrasound transducer suggests a simple, low-cost, battery-less, and long-range wireless readout system as compared to traditional biochemical sensing.