Cullen currently serves as a Director in the Systems Research Lab, where he leads a multi-disciplinary team of researchers investigating next generation computer architectures.
Prior to his current role he was interim director of the Sustainable Ecosystems Research Group at HP Labs where he led wide-ranging research into the sustainability of IT equipment, and the use of IT to improve the sustainability of customer ecosystems. During this time, he was also principal investigator of the Sustainable Data Center project which investigated the design and operation of data centers to reduce overall resource consumption. In previous roles, he has led research in thermal technologies over a variety of different length scales, from integrated circuits to data centers.
Cullen is a Fellow of the American Society of Mechanical Engineers and a Senior Member of IEEE.