The research uses of 3D printing are rapidly diversifying. The latest application is a lithium ion microbattery (subscription to Advanced Materials required to read full article). Unlike existing thin film batteries this printed microbattery is reported to have a similar performance to commercial batteries. Potential applications are for micro-robots and implantable medical devices.
The critical issues for these batteries will be their ability to hold enough charge to make them feasible for their intended uses, and to be able to be easily produced in large quantities.
Few will probably have concerns about uses in medical devices, but with current disquiet over electronic surveillance, swarms of autonomous micro-robots (government or privately controlled) are sure to meet resistance.