Roll coater having a recirculation loop for treating excess fluid

A roll coater comprising:

• a metering roll;
• an applicator roll,
• wherein a rotational axis of the metering roll and a rotational axis of the applicator roll are parallel and are positioned to create a gap between said metering roll and said applicator roll;
• a reservoir in fluid communication with said gap;
• a receptacle positioned to receive an excess fluid generated during operation of said roll coater;
• and
• a recirculation loop for receiving the excess fluid from the receptacle, for treating the excess fluid, and delivering a treated fluid into the reservoir,
• the recirculation loop comprising an agitation device,
• the agitation device comprising two or more ultrasonic transducers configured to operate at one or more frequencies selected based on a viscosity and a velocity of the excess fluid flowing through the agitation device,
• wherein the two or more ultrasonic transducers, operating at the one or more selected frequencies, are configured to produce one or more phase interferences in the excess fluid flowing through the agitation device thereby reversing polymerization of a sol-gel precursor within the excess fluid and reducing viscosity of the excess fluid while the excess fluid is flowing through the agitation device.