Disclosed are methods, compositions, and devices for an integrated, heterogenerous ion-exchange membrane-based plastic microfluidic biochip platform that can be used to detect multiple diagnostic markers present in real samples. Its various components can be easily integrated in a modular fashion for different applications. Automated control allows sequential and dynamic activation of different components on the chip. The integrated platform consists of three units and is designed to execute the following functions: (i) separation of the target biomolecules from the real sample, (ii) localizing and concentrating the targeted molecules at a specific location in the microfluidic chip, and (iii) detection of the targeted molecules using hybridization/docking events against a complementary ssDNA oligoprobe sequence or a specific antibody.