A method for fabricating a micro-structured surface of polyimide with open and closed pores

TL;DR

This paper introduces a laser-based method to fabricate micro-structured polyimide surfaces with controllable open and closed pores by adjusting laser fluence, enabling selective creation of porous structures in polymers.

Contribution

A novel laser processing technique for fabricating open and closed porous polyimide surfaces with precise control over pore formation.

Findings

Higher laser fluence increases pore size and number.

Fewer, larger pores form at high fluence due to pore coalescence.

Closed pores are created at very low fluence where minimal etching occurs.

Abstract

A new approach for fabricating open and closed porous structures based on laser processing is presented. Liquid polyimide (PI) was mixed with azodicarbonamide (ADC, ADA) which is a chemical blowing agent (CBA) and mixture was pre-cured in order to fabricate solid PI film. Porous PI was prepared by irradiating PI film mixed with azodicarbonamide. The PI film with azodicarbonamide was etched by laser ablation, and the CBA was decomposed by heat induced by the absorbed laser energy. The higher the laser beam irradiation, the more pores were fabricated due to the resulting increase in CBA decomposition from 27 mJ/cm2 to 40 mJ/cm2 per single pulse. Higher fluence at about 50 mJ/cm2 resulted in fewer and larger open pores, which were formed by the coalescence of small pores. In contrast, a closed porous structure was fabricated at a fluence of less than 1 mJ/cm2 because PI was barely etched. The proposed method can be sued to create open and closed micro porous structures selectively, and is not limited to thermosetting polymers, but is also effective with thermoplastic polymers.