This paper presents a new twin-membrane calorimeter chip for fast differential scanning calorimetry (DSC) with the Flash DSC 1 of Mettler-Toledo. The thin silicon nitride membranes enable scan rates in excess of 10 kK/s in heating and up to 4 kK/s in cooling for sample masses between 100 ng and 10 mu g in the temperature range of -100 degrees C to 450 degrees C. The time constant for cooling is about 12 ms, the power resolution is typically 0.1-0.5 mu,W,the temperature accuracy of non-calibrated chips is typically better than +/- 5 K. The paper also shows measurements for the scan-rate dependent thermal lag of the device, showing an empty sensor thermal lag of about 0.2 ms, and a mass dependent thermal lag of about 0.3 ms/mu g for Indium for a good thermal contact between Indium and membrane. (C) 2011 Elsevier B.V. All rights reserved.