With ever-increasing applications of IoT, and due to the heterogeneous and bursty nature of these applications, scalability has become an important research issue in building cloud-based IoT/M2M systems. This research proposes a dynamic SDN-based network slicing mechanism to tackle the scalability problems caused by such heterogeneity and fluctuation of IoT application requirements. The proposed method can automatically create a network slice on-the-fly for each new type of IoT application and adjust the QoS characteristics of the slice dynamically according to the changing requirements </span><span style="font-family:Verdana;">of an IoT application. Validated with extensive experiments, the proposed me</span><span style="font-family:Verdana;">chanism demonstrates better platform scalability when compared to a static slicing system.