Direct-Write Process Prints Electrode on a Spinal-Therapy Device

A direct-printing process developed by Micropen Technologies (Honeoye Falls, NY) has been used to apply patterned conductive and dielectric thick-film coatings onto a disposable spinal therapy component made from Radel polyphenylsulfone (PPSU). Supplied by Solvay Advanced Polymers LLC (Alpharetta, GA), this resin is used to form an electrically and mechanically reliable conductive electrode. The ability to use micropenning technology in conjunction with Radel PPSU provides medical device OEMs with an alternative to traditional metals and plastics for incorporating electrically conductive features onto complex parts, according to Micropen Technologies.

A direct-write technology, micropenning combines precision motion control with the ability to dispense flowable materials--typically thick-film polymeric inks--onto a substrate in a designed pattern. Capable of achieving accuracy and fine line widths down to 50 µm, this technology is suitable for applications involving 3-D objects and multiple functional materials--a common feature of medical devices that require electrical or electronic components, radiopaque markers, and drug dosing features.

The disposable spinal-therapy electrode is fabricated by depositing a conductive silver ink onto the exposed surface of the injection-molded component. Approximately 9 in. long and 0.25 in. wide, the intricate 3-D part features highly variable thicknesses. During the micropenning process, the Radel PPSU component is subjected to a range of solvents, UV radiation, and temperatures up to 150ºC. In clinical use, the disposable electrode's flexibility and fracture strength enable it to withstand repeated bending.

"We subjected the Radel PPSU component to considerable chemical abuse and high heat, and the material stood up to our process and maintained the mechanical properties that were critical to the application," remarks William Grande, vice president of research and business development at Micropen Technologies. The company had never worked with sulfone polymers before, but Radel provides film adhesion and biocompatibility, Grande adds.