Aerosol jet printing: An alternative to traditional microfabrication for biomedical electronics

The drive toward flexible electronics for use in biomedical applications is growing in demand due to cost-effective fabrication approaches along with flexibility and miniaturization capabilities. Flexible electronics can provide designers with thin form factors and high-density arrays to accommodate the development of wearable sensing monitors, point-of-care devices, and implantable electronics. Aerosol jet printing has emerged as an alternative to traditional microfabrication with lower costs, ease of fabrication, and expanded materials options due to lower processing temperatures. The advantage compared to other direct-write approaches is that it allows for integrated electronics to be printed on nonplanar surfaces with micron-scale resolution.

Aerosol jet printing is not without its challenges, many of which are still being understood. Optimization of the printing parameters for a given substrate and ink are still developing while substrate material choices and respective preparation for optimal adhesion remains an area for exploration. Further, to improve the overall performance and chronic reliability of these devices, accurate electrical and mechanical profiles need to be monitored over time. This work will discuss the current state-of-the-art and highlight work that systematically evaluates the effects of printing and curing parameters for silver nanoparticle and particle-free metallic inks. Characterization methods to understand the results of thermal curing and sintering along with monitoring the changes in the inks over time will be discussed. Mechanical and electrical reliability of AJP traces and their methodology will be reviewed and the challenges of making measurements without inducing damage will be highlighted. Lastly, examples of ongoing opportunities and current projects including high-density interconnects and leads for neuroprostheses that are beginning to utilize this technology will be presented. This emerging technology has the potential to provide cost-effective solutions for the growing flexible sensor market and provide designers with a more diverse set of materials options to support broader biomedical device applications.