Quantification of dose in plasma immersion ion implantation of polymer bone scaffolds: Probe diagnostics of a pulsed dielectric barrier discharge

Abstract

We demonstrate the ability of plasma immersion ion implantation to treat all surfaces of a porous polymer structure designed to act as a bone scaffold. We prove that the internal pore surfaces receive ion bombardment by examining the ultraviolet (UV) absorption spectrum of a thin polymer sheet placed inside pores of different diameters and locations. The current-voltage characteristics of a Langmuir probe in a pulsed dielectric barrier discharge are studied and interpreted to give measurements of the ion current drawn from plasma in the pores. An existing one-dimensional model of the plasma is adapted and combined with the Langmuir probe measurements to predict the ion dose to the pore surfaces. Our prediction agrees with measurements from UV absorption.

Optical properties of plasma‐treated PEEK: Monitoring colour and crystallinity for applications in medicine and dentistry using ellipsometry

“…Plasma immersion Ion implantation was carried out using a dielectric barrier discharge (DBD) apparatus described elsewhere. [9] Nitrogen gas was used at a pressure of 500 mTorr, with the DBD powered by a Rup-6 switchmode pulsed power supply (Elektroteknik GmBH Germany) with a square wave amplitude of −10kV, a square wave amplitude of −10kV, 40 s pulse width and 1 kHz frequency with a pulse rise time of ~220-250 ns.…”

“…Plasma immersion Ion implantation was carried out using a dielectric barrier discharge (DBD) apparatus described elsewhere. [ 9 ] Nitrogen gas was used at a pressure of 500 mTorr, with the DBD powered by a Rup‐6 switch‐mode pulsed power supply (Elektroteknik GmBH Germany) with a square wave amplitude of −10kV, a square wave amplitude of −10kV, 40 $$$$s pulse width and 1 kHz frequency with a pulse rise time of ~220–250 ns. The PEEK sheets were subjected to PIII treatment for treatment times of 0, 0.5, 1, 2, 5, 10, 15, 20, and 30 min, to give a set of ion fluences on the surface of each PEEK sheet proportional to treatment time.…”

“…[ 7,8 ] A unique feature of the PIII process is its ability to treat the internal surfaces of porous structures, providing a complete internal and external surface modification. [ 9 ] Bombarding ions deposit energy through nuclear displacements, electronic excitation and ionisation events, leading to persistent free radicals, cross‐linking, hydrogen exclusion, carbonisation [ 10,11 ] and enabling covalent linking of molecules. These modifications are accompanied by changes in the electronic band structure, conveniently monitored through optical property measurement and evident as a darkening of the material in the visible spectrum.…”

“…Previous publications have shown that greater absorption in the UV is usually accompanied by a visible darkening of a transparent polymer. [ 9,10 ] While the visible darkening of PEEK from PIII is expected to be minor, the optical properties should be monitored to ensure the colour of the implant remains aesthetic.…”

Plasma ion implantation of 3D‐printed PEEK creates optimal host conditions for bone ongrowth and mineralisation

“…[15] PEEK also exhibits low thermal and electrical conductivity, and with growth of bone cells into a porous PEEK structure, it is an excellent material for load-bearing applications. [16] For the above reasons, the use of PEEK may lead to better ultimate outcomes if bone cell adherence and mineralisation could be optimised. Hydrophobicity and the lack of biological activity of PEEK in its native state are a critical barrier.…”