Flexible Induction Heater Based on the Polymeric Thin Film for Local Thermotherapy

Local delivery of physical energy, such as heat, is promising for the treatment of target lesions without the unintended distribution of heat to other normal tissue. However, the heating device must be equipped with an external power source or strong magnetic field to operate the device, and many of them are too large to be placed inside the body. In this regard, wireless, lightweight, flexible electronics can be used for the miniaturization of implantable devices. In this study, a flexible induction heating (IH) device is reported that integrates inkjet-printed wirings and flexible polymeric thin films, specifically Au nanoink-based wirings (thickness: 1.5 µm) and a biodegradable poly(D, L-lactic acid) (PDLLA) thin film (thickness: 5 µm). A unique method of transferring the inkjet-printed Au nanoink wiring onto the PDLLA thin film realizes the integration of the following technical features in one device: biocompatible packaging, a printed IH system, and body conformability. The resulting thin-film IH device is successfully placed on a hepatic lobe of a beagle dog, which allows for a local increase in temperature of 7 °C after 1-min power feeding without tissue inflammation. The thin-film IH device is expected to provide minimally invasive thermotherapy when combined with endoscopic surgery.