This paper presents a new method to manipulate microdevices’ membranes using nano-electrodeposits for directional microphones in hearing aid applications. The key to achieving high directionality is to minimize the mismatch of the omni-directional microphones using in-situ tuning by the integrated electrodeposition of metallic nanostructures. The nanostructures can be grown/retracted upon external bias at room temperature. The growth/retraction changes mass/stress distribution on the diaphragm of microdevices to precisely manipulate sensitivities to incoming acoustic waves. The omni-directional microphones are capacitive and have a parylene membrane integrated with the nanostructures. The microphone capacitance can be tuned up to 0.7 dB and acoustic mismatch reduces by 1.2 dB. This represents directivity index (DI) increase of 1.2 dB, which is crucial to achieve high directionality in composite microphones. The technology has many applications, including post-packaging trimming and calibration of micro-devices.