Towards ghz ultrasound enabled noninvasive hydrogel metrology for mechanobiology

This paper presents a noninvasive method for the measurement of transient mechanical properties for hydrogel swelling using a CMOS-integrated piezo MEMS ultrasound imager operating at similar to 1.8 GHz. The noninvasive measurement and tuning of hydrogel stiffness is crucial for creating cell culture environments with different mechanical properties to study the mechanical interactions between cells and the surrounding matrix [1]. We present a novel method for real-time and noninvasive measurement of hydrogel swelling using GHz ultrasound reflectometry. We measured five samples from seven different batches with water contents varying from zero (dry) to 1000 mu L water per 100 mg of hydrogel-the ultrasound-based measured bulk modulus of hydrogel samples (similar to 1-4.5 GPa) verified by micro indentation showing closely matching trends.