Deterministic lateral displacement (DLD) devices have demonstrated great promise in separation of micro and nano-sized particles, with important applications in biomedical research and healthcare monitoring. This paper introduces a new cascaded multi-section DLD approach toward expanding the dynamic range of particle sizes separated. A robust model has been developed to analyze the design tradeoffs and practical fabrication limits of this new approach. Results show that by cascading multiple sections of increasingly smaller gap size and critical separation dimension, a wide spectrum of size fractionation dynamic ranges and minimum separation resolutions can be achieved. Moreover, the presented model allows designers to visualize the cost of achieving various performance goals in terms of overall device size. Model results based on DLD theoretical equations are first presented, followed by model results for both circle and I-shaped pillar options that apply scaling restrictions associated with their practical fabrication limits.