An etch release process capable of releasing long resonant gate transistor bridges from a sacrificial layer has been studied as a step towards developing a system to mimic the cochlear mechanism inside the human ear. The developed etch release process involves the use of a gentle etch tool that is capable of a clean and damage-free etch release. The influence of temperature and oxygen/nitrogen gas flow rates on the undercut etch rates and the profiles of photoresist and polyimide sacrificial layers have been investigated. An array of aluminum bridges of length 0.278-1.618 mm, which cover the frequencies from 1 to 33.86 kHz, has been designed and released from a sacrificial layer. The resonating beams have been measured. (C) 2010 American Vacuum Society. [DOI:10.1116/1.3504892]