Microfabrication of Mo Electrodes on Bioabsorbable Polymer Substrates and Its Application to a Needle-Type Electrode Formation

Abstract Bioabsorbable polymers are highly attractive as safe and minimally invasive materials for constructing implantable and semi-implantable medical devices used in/on the human body. Currently, microfabrication for device miniaturization is under investigation. This study proposes the use of bioabsorbable polymers including poly(L-lactic acid) (PLLA) as substrate materials for highly safe and minimally invasive biomedical sensors. The aim is to design a fabrication technique for forming metal wires and electrodes on PLLA substrates, which are the most commonly used bioabsorbable materials, for future applications as minimally invasive biomedical devices including microneedles. PLLA substrates are subjected to industrially feasible fabrications including molding, O 2 plasma treatment, sputtering, and laser ablation. Then, the substrates are characterized by atomic force microscopy, contact angle measurements, X-ray photoelectron spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. Adhesion at the metal/polymer interface is enhanced through a combination of physical and chemical effects to improve the quality of metal wires formed on the substrate. Finally, microneedle-type electrodes are fabricated using the developed microfabrication technique are demonstrated. The microfabrication of bioabsorbable polymers and metals is anticipated to contribute to the development of highly safe and minimally invasive medical devices used in/on the human body. The novel microfabrication technique developed in this study is applicable to (i) bioabsorbable polymer/metal materials without the use of chemical solvents and harsh conditions, and (ii) the formation of metal electrodes on both two- and three-dimensional microstructures. Graphical Abstract