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A multipolymeric fabrication process using polymethlymethacrylate (PMMA) as a membrane layer was demonstrated for a robust dermal patch, called the bio-fluidic integrable transdermal (B–FIT) microsystem. B–FIT is a noninvasive microdevice, in the form of an adhesive patch, which samples biomolecules from interstitial fluids using controlled thermal ablation and encapsulated fluid that is released during biomolecule collection. Thus, a membrane material was needed that could encapsulate the fluid and easily liberate it, on demand, with minimal energy and compatibility with the fabrication process. PMMA was selected as the most promising membrane material for the B–FIT as against SU-8 since it had the required properties of low melting temperature (120–150 °C), good adhesion to pre-existing B–FIT materials (gold and SU-8), and could be easily spin-cast into thin uniform films. However, PMMA is not inert towards various solvents like acetone, photoresist developers, hence, a process was developed to protect PMMA from being attacked by the solvents used during the fabrication of the device. In this process, several strategies were employed such as crosslinking and application of thin protection layers on the PMMA. By exploring these fabrication strategies, PMMA was successfully patterned and the desired encapsulation and rupturing of the membrane was obtained. © 2004 American Vacuum Society.