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This invention describes a chemical micro-sensor that operates as an electro-mechanical switch. A polymer with functional groups specific to the species of interest is deposited using initiated chemical vapor deposition (iCVD) onto an approximately 100 nm-thick micro-cantilever. Selective binding of the species of interest with the polymer coating induces stresses that result in a large deflection (relative to existing cantilever-based chemical sensing methods) at the cantilever tip, on the order of 50 μm. This large deflection causes the cantilever to come into contact with a pad, completing an electrical circuit. Instead of producing a graduated response to the degree of chemical binding, this system generates a binary signal indicating the presence of the species of interest at a predetermined critical concentration. Relying on binary switching instead of analog measurements virtually eliminates power draw when the sensor is not activated and dramatically simplifies the logic circuitry required to condition and process the signal. The on/off circuitry is also more robust against ambient interference than existing analog sensors.