Richard C. Svrluga

Enhanced bioactivity and osseointegration of PEEK with accelerated neutral atom beam technology

Polyetheretherketone (PEEK) is growing in popularity for orthopedic, spinal, and trauma applications but has potential significant limitations in use. PEEK is biocompatible, similar in elasticity to bone, and radiolucent, but is inert and therefore does not integrate well with bone. Current efforts are focusing on increasing the bioactivity of PEEK with surface modifications to improve the bone-implant interface. We used a novel Accelerated Neutral Atom Beam (ANAB) technology to enhance the bioactivity of PEEK. Human osteoblast-like cells seeded on ANAB-treated PEEK result in significantly enhanced proliferation compared with control PEEK. Cells grown on ANAB-treated PEEK increase osteogenic expression of ALPL (1.98-fold, p < 0.002), RUNX2 (3.20-fold, p < 0.002), COL1A (1.94-fold, p < 0.015), IBSP (2.78-fold, p < 0.003), and BMP2 (1.89-fold, p < 0.004). Cells grown on these treated surfaces also lead to an increased mineralization (6.4-fold at 21 days, p < 0.0005). In an ovine study, ANAB-treated PEEK implants resulted in enhanced bone-in-contact by 3.09-fold (p < 0.014), increased push-out strength (control 1959 ± 1445 kPa; ANAB 4068 ± 1197 kPa, p < 0.05), and evidence of bone ingrowth at both the early (4 weeks) and later (12 weeks) time points. Taken together, these data suggest that ANAB treatment of PEEK has the potential to enhance its bioactivity, leading to bone formation and significantly decreasing osseointegration time of orthopedic and spinal implants. ANAB treatment, therefore, may significantly enhance the performance of PEEK medical implants and lead to improved clinical outcomes.

Impact of gas cluster ion and accelerated neutral atom beam surface treatments on the laser-induced damage threshold of ceramic Yb:YAG

We describe the application of the gas cluster ion beam (GCIB) and of the accelerated neutral atom beam (ANAB) surface treatments to ceramic Yb:YAG. We demonstrate that these techniques allow accurate control of ceramic Yb:YAG surface characteristics and constitute an alternative to conventional surface finishing techniques. In this study, we analyse the impact of angstrom level polishing and surface nano-texturing on laser induced damage threshold (LIDT) in the nanosecond pulsed regime of uncoated and antireflective coated ceramic Yb:YAG samples. We show that both techniques allow meeting the requirements on resilience to laser irradiation at fluence levels characterising high-energy laser systems. Moreover, we show that surface nano-texturing improves the LIDT of coated samples, possibly through an improvement in adherence of coatings to ceramic Yb:YAG substrates.

Accelerated neutral atom beam (ANAB) technology for nanoscale surface processing

Many difficulties and limitations of surface processing by traditional ion beam techniques are associated with the electrical charges that are fundamental to ion acceleration. Flux neutralization approaches used to minimize space charge repulsion effects and neutralization methods employed to avoid surface charge accumulation and damage phenomena complicate the use of ion beams in many situations, particularly so as device dimensions approach nano-scale. It has long been recognized that simplified fabrication processes and superior nano-level processing capabilities would be possible if process beams comprised of only neutral atoms having adequate and controllable energies could be generated. The obstacle to creating such beams has always been the problem of how to remove all electrical charges from a beam of ionized atoms after acceleration. This paper describes a method known as Accelerated Neutral Atom Beam (ANAB) in which energetic neutral atoms are produced by causing large numbers of neutral atoms to be released from the individual gas clusters within a stream of high energy gas cluster ions and then using an electrostatic field to eliminate residual charged species from the beam. The ANAB technique provides high flux collimated beams of energetic neutral atoms that have average energies which are controllable from less than 10 eV per atom to more than 100 eV per atom, a range found to be ideal for many nano-scale surface modification actions. Available neutral beam species include virtually any element or molecule that exists as a gas at room temperature. ANAB processes are useful for precise sputtering, nano-level surface smoothing, extremely shallow doping, highly selective etching, ultra-thin film deposition, surface passivation, various surface specific molecular transformations, and for a range of other ultra-shallow surface actions. Due to its highly collimated nature, ANAB offers excellent performance for nano-scale patterning and for uniform depth processing of structural geometries with varied aspect ratios. ANAB is being employed in a number of areas, including medical implants, other medical and biological devices, optics, MEMS, semiconductors, and metrology.