Anisotropic pyrochemical microetching of poly(tetrafluoroethylene) initiated by synchrotron radiation-induced scission of molecule bonds

Abstract

We developed a process for micromachining polytetrafluoroethylene (PTFE): anisotropic pyrochemical microetching induced by synchrotron X-ray irradiation. X-ray irradiation was performed at room temperature. Upon heating, the irradiated PTFE substrates exhibited high-precision features. Both the X-ray diffraction peak and Raman signal from the irradiated areas of the substrate decreased with increasing irradiation dose. The etching mechanism is speculated as follows: X-ray irradiation caused chain scission, which decreased the number-average degree of polymerization. The melting temperature of irradiated PTFE decreased as the polymer chain length decreased, enabling the treated regions to melt at a lower temperature. The anisotropic pyrochemical etching process enabled the fabrication of PTFE microstructures with higher precision than simultaneously heating and irradiating the sample.

Rapid X-ray Fabrication of Microstructured Polytetrafluoroethylene Substrates by Anisotropic, Pyrochemical Microetching

“…These results are attributed to the vaporization temperature of the PTFE fragments, which depends on the scission ratio of the PTFE polymer main chain. [7,10] The fragments of the PTFE polymer liquefy during heating; larger fragments remain as residual dross while smaller fragments are vaporized. Consequently, the anisotropic, pyrochemical etching can proceed to a considerable depth.…”

“…In addition, this result suggests that the ablation mechanism of PTFE is dependent on the Xray energy. Our previous studies reported [7] that Xrays with higher photon energies could penetrate to a considerable depth within the PTFE substrate; however, Nagai et al [4] and Zhang et al [2] demonstrated that the ablation of PTFE is driven by the SR-induced decomposition reaction with lowenergy photons (< 1 keV). Therefore, it is useful to investigate the dependence of PTFE etching on photon energy.…”

“…Heating was used to induce the anisotropic, pyrochemical etching of the irradiated areas of the PTFE substrates. [7] …”

“…In our previous studies, [5,6] the lateral structure has been distorted, and its positioning has been misaligned. Recently, anisotropic, pyrochemical etching has been investigated by Yamaguchi et al [7] The etching mechanism was related to the scission of PTFE main chains by X-ray irradiation with high photon energies ranging from 4 to 12 keV. Heating the PTFE after X-ray irradiation induces the evaporation of -CF 2 -fragments of the polymer main chain, which exhibit a significantly reduced vaporization temperature compared to the unirradiated polymer.…”

“…Recently, it has been determined that synchrotron radiation (SR) can facilitate micron-scale etching of PTFE at a very rapid rate. [2][3][4][5][6][7] Recently, several studies have reported on the microetching of PTFE substrates using SR irradiation. Zhang et al [2] have demonstrated the direct microetching of PTFE substrates with a high aspect ratio using an SR-induced ablation reaction.…”