Stiffness tunable implanted electrode enabled by magnetic liquid metal for wireless hyperthermia

Flexible electrodes with favorable compliance to alleviate the mechanical mismatch in tissue-electrode interface exert a critical role in the stability of long-term implantation. Despite the tremendous efforts on developing innovative materials for tuning the mechanical strength of electrodes, integration of stiffness tunable and conductive merits in one electrode is still hard to realize. Here, an implantable electrode with tunable stiffness of 5 orders of magnitude was proposed for wirelessly enhanced electromagnetic therapy to both enable the insertion process and retain flexible conformability to surrounding biological tissues. The electrode, fabricated by magnetic liquid metal (MLM) without tethered system, can generate inductive heat for hyperthermia under exposure to alternative magnetic fields (AMF). The MLM was developed to induce enhanced electromagnetic heating and the underlying mechanism is further revealed. The magnetic liquid metal enabled flexible electrode (MLMFE) was further demonstrated with excellent biocompatibility and biosafety via in vitro and in vivo administration. The hyperthermia enabled by MLMFE is highly effective in tumor growth retardation and survival time prolongation. After implantation, multiple treatments would enhance the therapeutic effects. The unique merits of the MLMFE provide broad application scenarios in tumor therapeutics and long-term monitoring and stimulation of the nervous systems.