One-Step Preparation of Ethyl Cellulose Films with Asymmetric Graded Pores for Low Dielectric Printing Substrates

The innovation of communication technology and the proliferation of the Internet of Things have propelled the exploitation and application of mid-to-low end and disposable radio frequency devices, alongside the development of low dielectric materials. Traditional petroleum-based low dielectric substrates, led by polyimide, present several challenges, including higher cost, non-renewability, difficulty in disposal and recycling, rendering them unsuitable for disposable applications. In this study, the asymmetric ethyl cellulose (EC) porous film with dense skins is prepared in one step by the evaporation process of EC/ethanol/H₂O solution. The synergistic pore-forming mechanism of the dry phase inversion technique and breath figure phenomenon is proposed based on EC pore morphology. The relative permittivity of the asymmetric EC porous film is 2.02 ± 0.03 (6 GHz), demonstrating satisfactory dielectric stability, printing adaptability, and bending ability. The EC in discarded printed antennas and remnants from the film-making process can be separated and recovered through a simple dissolution and centrifugation process. The green and simple preparation process, extremely low manufacturing cost, excellent recyclability, and potential roll-to-roll process adaptability make asymmetric EC porous film highly competitive in the mid-to-low end and disposable centimetre wave radio frequency device substrate fields.