Coffee Joulies are small, stainless-steel capsules containing a phase-change material; the capsules were designed to be placed in a cup of coffee in order to cool coffee that is too hot then slowly release the heat to keep the coffee warm. The company was founded by Dave Petrillo and Dave Jackson, mechanical engineers from Pennington, New Jersey. A similar concept using phase change materials, but integrated into the walls and bottom of a cup, had been invented by the Fraunhofer Institute for Building Physics in 2009. In 2013 the founders were contestants on Shark Tank and raised $150,000.