Injectable fiber batteries for all-region power supply in vivo

Implantable batteries are critical for operation of most implanted electronic devices that are revolutionizing the healthcare field nowadays. However, the employed electrolytes for existing implanted batteries are mainly based on toxic organic solutions, which poses serious potential safety problems when they are implanted into the human body. Furthermore, current implanted batteries are generally bulky and rigid with stiff encapsulations, so they mechanically mismatch soft biological tissues with potential foreign body responses. Here, we present a biocompatible and rechargeable fiber battery that used carbon nanotube hybrid fibers as electrodes and did not require encapsulation to realize much higher softness. The fiber battery can be thus injected into various regions of the body through a mini-invasive syringe and delivered a power density of 78.9 mW cm−3in vivo, which is sufficient to drive various implanted electronic devices. The injectable fiber battery formed stable interfaces with tissues and showed high performances in the brain, heart and subcutis. As a demonstration, it was injected into the subcutis of a mouse to power an implanted sensor for respiration monitoring.