Phononic crystal sensor for liquid property determination

Acoustic band gap materials, so-called phononic crystals, provide a new sensor platform. Phononic crystals are periodic composite materials with spatial modulation of elasticity, mass density as well as longitudinal and transverse velocities of elastic waves. When utilized as sensor, the input parameter to be measured changes characteristic properties of the phononic crystal in a distinct manner. These changes can be detected by measuring the transmission behavior of ultrasonic waves through the phononic crystal. The most optimal feature for detection is a sharp isolated transmission peak which corresponds to the input parameter. When applying as liquid property sensor one component building the phononic crystal is the liquid to be analyzed. Here we present recent results gathered from different sensor realizations. In the second part we report on experimental investigations based on laser vibrometry which provide deeper insides to the so-called extraordinary transmission. These analyses reveal that structural resonance effects are responsible for the smart properties of the device.