Flexible Bandpass Filter Fabricated on Polyimide Substrate by Surface Modification and In Situ Self-Metallization Technique

Abstract

Polymer, especially polyimide (PI), is the best suitable substrate material for the design of flexible electronics. The compact silver can be reduced on the surface of PI films by surface modification and in situ self-metallization technique. The formed silver layers have good electrical and mechanical flexibility. A flexible bandpass filter on a PI flexible substrate by surface modification and in situ self-metallization technique at room temperature are presented in this work. Measured results show that the proposed flexible bandpass filter could achieve a fractional bandwidth of 80.8% with an insertion loss (IL) of less than 0.6 dB. The performance of the designed filter is almost constant under different bending, folding, and rolling conditions. The formed silver layers also present good adhesion with PI substrates. This technology provides an alternative approach for manufacturing flexible filters without high-temperature thermal annealing, costly equipment, and vacuum conditions.

2.45 GHz natural polymer‐based flexible bandpass filter exploiting laser structuring

“…We can find in literature flexible bandpass filters fabricated on polymer substrates using self-metallization technique 15,22 and photolithography with chemical etching 23,24 but compared to our work, the substrate used is not biosourced. We can also find flexible filters fabricated on paper substrates 25 using photolithography combined with chemical etching and another sacrificial substrate, but then the issue of hydrophobicity arises.…”

“…The bandpass filter proposed shows a minimum degradation under physical deformation to be used advantageously in wearable applications. Compared to the literature, 15,23 it can be noticed that the filter's performance is less affected under mechanical deformation.…”

“…One can find in literature some works dedicated to flexible filters on polymers. Usually, photolithography combined with chemical etching 14 or inkjet printing 15 is employed for the fabrication. To avoid damaging the natural substrate by chemical products, we propose an original method of fabrication that relies on copper adhesive tape and laser structuring.…”

An Assessment of Surface Treatments for Adhesion of Polyimide Thin Films

“…However, this material is chemically inert and presents a smooth surface. Therefore, their proper adhesion with other materials requires specific surface treatments [9][10][11].…”

In Situ Growth of Silver Film on Polyimide with Tuned Morphologies for Flexible Electronics

“…Therefore, much attention has been paid to the in situ Ag film growth on polyimide via self-metallization technique in recent years due to the excellent conductivity and good adhesion between Ag and PI substrate. The characteristic Ag pattern can be fabricated by combing the self-metallization and inkjet printing techniques, which has been applied for different kinds of flexible sensors. − …”