A power-free single channel microfluidic device was designed for rapid and sensitive detection of cadmium (Cd2+). Unmodified gold nanoparticles (AuNP) colloid was prepared by an electrochemical method to detect Cd2+ into water upon colorimetric assay and electric resistance. The detection method based on color changes resulted from AuNP aggregation and their impact on surface Plasmon resonance. Colloidal solutions of AuNPs have high extinction coefficients and absorption band in the visible region of the UV-Visible spectrum. Its position depends upon the Au particle size and inter-particles distance. Therefore, a well-designed chemical interaction between the analytic and AuNPs surroundings resulted in aggregates and changes in surface plasmon resonance band position and width that lead to visual detection of Cd2+. These visual results could be observed by the naked eye when the mixture color changed from red in blue with Cd2+ concentration. Optical property’s changes with Cd2+ concentrations in water were studied via UV-Visible spectrometer. Using PDMS surface modified to construct microfluidic device supported to get stable electric resistance values for AuNP colloid and Cd aqueous solution mixture. Electric resistance results accomplished with UV-Visble results could be employed to detect low ion concentrations in water (10 µM) sensitively.