Flexible, transparent electronics for biomedical applications

Abstract

The development and integration of flexible biocompatible electronics is of considerable interest in the biomedical community. Electronic and fluidic based monitoring and therapeutic platforms can be contoured into comfortable, low profile devices suitable for implanting in the body or for wearing on the body or in clothing. Truly integrated bioflexible devices would incorporate electronics, optics, photonics, wireless, fluidics, mechanical components, and power systems on a single flexible biocompatible substrate. Continued development of applications of this technology requires further development of biocompatible, flexible films with integrated electronics which can be mass produced at low cost. In this work, we demonstrate the fabrication of flexible printed circuits on Cyclo Olefin Polymer (COP) thermoplastic as a substrate material. COP is an attractive polymer for integrated bioflexible devices due to demonstrated biocompatibility and excellent material properties, such as high transparency over a wide band of wavelengths, low water absorption, and good mechanical properties. On significant challenge to building bioflxible devices on polymer films (such as COP) is the need for metalizing and patterning traces on these materials at low cost, and in a scalable manner. In this paper, we report work that utilizes a new technique for patterning metals on polymers that can result in low cost manufacturing of electronic circuits on biocompatible films such as COP. The process uses high intensity UV light that is directed through a quartz mask to selectively irradiate a film of COP. After processing, the material can be treated and subsequently metalized using electroless plating techniques. The great benefit of this approach is that no photoresists steps are needed-no coating, exposing, developing, etching, or stripping is required for the creation of the final device. Furthermore, the process can pattern traces at high resolution (<;2 microns) and can coat the insides of through hole vias, allowing multi-layer electronics to be produced. This greatly simplifies the manufacture of the circuits and reduces production cost considerably, when compared to conventional processes such as sputtering and etch. We demonstrate the production of electronic circuits on COP for the purpose of making bioelectronic devices and characterize some of the main properties of the device. We discuss the advantages of this approach and identify some of the manufacturing pitfalls.