An assay device and method of assaying the application of energy to a plurality of samples in vitro. The assay device includes a housing, an array, and a control module. The housing includes a socket sized to receive a culture plate. The array includes a plurality of emitters and is positioned within the housing adjacent to the socket so that the plurality of emitters are each aligned with at least one culture well of the culture plate when the culture plate is received in the socket. The control module is operably coupled to the array and is configured to individually drive the plurality of emitters. The control module is configured to drive at least two of the plurality of emitters at different frequencies simultaneously.
