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Missouri S&T discovers low-cost manufacturing of bioresorbable electronics: Laser printing bioresorbable electronics with nanoparticles
Bioresorbable electronics have received great attention in recent years, because of their great promise in healthcare and environmental protection. These devices operate only over designated periods and dissolve afterward into biologically safe compounds. In healthcare, bioresorbable sensors have the potential for post-surgical monitoring of organ, implant, and wound health without the need for a second surgery to remove them. These devices could also potentially address environmental issues related to the increasing demands for the latest electronics gadgets and the accelerated the rate of obsolescence. However, manufacturing techniques for these devices are currently based on traditional Integrated Circuits (IC) chip fabrication methods, requiring expensive optical patterning and vacuum deposition steps. A typical device may take weeks to fabricate and cost thousands of dollars. While mass production could certainly reduce time and cost, the IC based process will never be economically competitive with Printed Circuit Boards (PCBs), which cost pennies per square inch.
Direct printing, as compared to IC based process, has great advantages in reducing the cost per area for producing large area electronics. However, a major problem is the difficulty in printing bioresorbable materials, such as Zinc, Magnesium and others. Such materials can easily react with hydroxyl, oxygen, and nitrogen in a typical printing environment and may degrade readily. In addition, the sintering step, which follows the printing step to fuse and connect printed materials, is technically challenging. For example, it is notoriously difficult to sinter Zn nanoparticles due to the surface oxide that hinders the fusion of two particles.
Prof. Heng Pan from the Department of Mechanical and Aerospace Engineering at Missouri University of Science and Technology points out that laser sintering of nanoparticles is a viable approach for direct printing bioresorbable electronics. He and his collaborator Prof. Xian Huang of Department of Biomedical Engineering at Tianjin University, and co-workers, discover that the sintering of Zn nanoparticles can be greatly facilitated by evaporation and condensation. Based on this, a low-cost manufacturing method for bioresorbable conductors is recently unveiled in a Communication published in Advanced Materials (http://dx.doi.org/10.1002/adma.201700172). “The new method can direct print patterned Zn conductors on bioresorbable polymers with conductivity close to bulk values,” Prof. Pan states.
A high speed scanning laser is used to direct write oxide-free Zn conductors in ambient environment. This simple method allows easy integration onto a roll-to-roll platform for continuous production. The versatility and feasibility of this method are demonstrated by the manufacturing of functional strain gauges, which could be used as environmental friendly sensors. It is also shown that the devices can dissolve completely in water after 1-2 hours. The facile method opens up pathways towards the low-cost bioresorbable electronics, bringing laboratory discoveries to actual applications.