Postimplantation pressure testing and characterization of laser bonded glass/polyimide microjoints

Abstract

The stability of the laser bonded titanium coated glass/polyimide microjoints were studied in vivo by implanting on a rat brain surface for 10 days. In the current state, the strength of the joints were measured by a specially designed instrument called "pressure test" equipment where the samples were subjected to a variable pressure load (using high pressure nitrogen) controlled by a pressure regulator. The strength of the joints seems to degrade by about 28% as a result of soaking in rat brain. The bond degradation in rat brain implants is similar compared with those soaked in artificial cerebrospinal fluid (CSF) solution. Polyimide uptakes water through existing pores in it and also water gets in the joint region through the edges of the samples. Water might have caused oxidation of the chemical bonds which are thought to have formed by the laser fabrication process. A separate set of samples were created using same parameters for testing the hermeticity of the laser bonds. The samples were also exposed to rat brain CSF and were tested for hermiticity at the end of 10 days exposure time. It was observed that the implanted samples retained their hermeticity although the bond strength degraded by about 28%.

Welding methods for joining thermoplastic polymers for the hermetic enclosure of medical devices

“…cm 3 /s, and it was concluded that the polyimide-titanium seal was nearhermetic. Post-implantation assessment after implant in a rat brain for 10 days showed that hermeticity was maintained, however, a 28% reduction in bond strength was observed [111]. The group concluded that the seals could be effective for short-term implants and that further optimisation was required for long-term implantation.…”

Laser Engineering of Surface Structures

“…Mian et al used transmission laser welding of titanium-coated glass-polyimide joints to demonstrate that optical fiber laser-welded joints provided stronger bonds than diode laser-welded joints [29]. In a recent study, Mian et al showed that laser-welded, titanium-coated, glass-polyimide micro-joints lost 28% of joint strength after incubating with rat brain tissue for 10 days [30]. Their work indicates that additional efforts are needed for the use of polymer laser welding in medical implants.…”

Laser micro- and nanofabrication of biomaterials

“…29 In a recent study, Mian et al showed that laserwelded, titanium coated, glass-polyimide microjoints lost 28% of joint strength after incubating with rat brain tissue for 10 days. 30 Their work indicates that additional efforts are needed for use of polymer laser welding in medical implants.…”