Objective: Microfluidic technology enables precise control of cellular microenvironments for drug screening, yet its application in evaluating dose-dependent drug responses and metastatic behaviors of breast cancer cells remains underexplored. This study aims to develop a novel microfluidic platform for high-throughput, low-cost drug testing. Methods: A concentration-gradient microfluidic chip with six parallel gradient generators was designed to simultaneously deliver 0–100 μM gradients of doxorubicin/paclitaxel to MCF-7 and MDA-MB-231 cells. Cell viability was quantified via on-chip Calcein-AM/PI staining, and migratory dynamics were analyzed through time-lapse imaging. Comparative validation with 96-well plate assays was performed. Results: MDA-MB-231 showed higher doxorubicin resistance (IC50: 48.3±2.1 μM) than MCF-7 (IC50: 22.7±1.8 μM, *p*<0.01); Chip-derived IC50 values strongly correlated with conventional methods (R²=0.94) while reducing reagent use by 90%; Sub-lethal doses (10–20 μM) enhanced cell migration (*p*<0.05). Conclusion: This microfluidic system provides a physiologically relevant and cost-effective alternative for personalized drug response profiling, with the potential to accelerate precision oncology research.

Microfluidics, Breast Cancer, Drug Resistance, Gradient Generator, Metastasis