(245g) Measurement of Dynamic Mechanical Properties of Hydrogels Using Piezoelectric-Excited Millimeter Cantilever Sensors

The dynamic mechanical properties of hydrogels are an important consideration for many biomedical applications, including drug delivery and tissue engineering. To date, differences in cell type and activity have been linked to the mechanical properties of 3D cell culture environments. While dynamic mechanical analysis (DMA) of hydrogels is critical for providing characterization data, a high-throughput sensor-based DMA technique that can be integrated with 3D cell culture systems would present novel opportunities for monitoring and control of hydrogel-based material systems. We present a piezoelectric-excited millimeter cantilever (PEMC) sensor that provides real-time dynamic mechanical property information in hydrogels. Sensor impedance magnitude, phase angle, and Q-value of the cantilever sensor’s second and third resonant modes were continuously tracked during the curing of multiple hydrogels, including alginate and poly(ethylene glycol) diacrylate (PEGDA). We show that PEMC sensors facilitate measurement of hydrogel curing kinetics in chemically- and photo-cured systems and viscoelastic properties of hydrogels over the range 30 - 120 kPa. Net changes in sensor response upon hydrogel curing correlated with hydrogel modulus measured through DMA. Sensor data and fluid-structure interaction models of dynamic cantilevers yielded values of cured hydrogel modulus at high frequency strain rates. Applications for in situ monitoring of 3D cell culture mechanical properties are discussed. This work created a sensor-based approach for monitoring the viscoelastic properties and gelation kinetics of hydrogels that opens up multiple opportunities in biomedical, biomaterials, and biomanufacturing applications.