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

Abstract

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.

Recent advances in inkjet-printing technologies for flexible/wearable electronics

“…There are a variety of inks for inkjet printing, which can be roughly divided into four categories according to electrical functionality. Conductive inks, such as Ag, 60,67,91,94,107,110,112,158 Au, 150 PEDOT:PSS, 21,67,92,103,116 rGO, 58,59,146 MXene, 26,59,146,147 which are mostly used to make conductive wires and electrodes due to the high electrical conductivity. Inks like barium titanate 62 and yttrium aluminium oxide (YAlO x ) 63 can be adopted as dielectric ink, which is common in the manufacture of field effect transistors and capacitors.…”

“…Fujie et al 150 designed a flexible induction heater integrated with inkjet-printed Au wiring and flexible biodegradable poly( d , l -lactic acid) (PDLLA) thin film (Fig. 15a), followed by a transfer process.…”

Flexible Thin‐Film Neural Electrodes with Improved Conformability for ECoG Measurements and Electrical Stimulation

“…Flexural rigidity is a measure of the resistance to bending [40] and is often used as a measure of flexibility in thinfilm devices. [34] The flexural rigidity (D) is defined by the following equation:…”

Flexible Inkjet-Printed Heaters Utilizing Graphene-Based Inks

“…In chemical sensors, microheaters are usually utilized for either enhancing detection performance or assistance in degassing [ 3 , 4 ]; more specifically, in metal–oxide gas [ 5 ], ammonia [ 6 ], fully printed SnO 2 gas [ 7 ], HCHO [ 8 ], and humidity [ 9 , 10 ] sensors. Microheaters are also quite common in numerous biodevices, where the operating temperature requires precise control [ 11 , 12 , 13 , 14 , 15 ]; analytical paper-based devices incorporating such printed heaters have been developed [ 13 ], alongside local thermotherapeutic printed devices [ 14 ] and devices for drug metabolism research [ 15 ]. Various additive deposition techniques such as printing have been reported for effective selective patterning and fabrication of such devices on flexible [ 16 , 17 , 18 , 19 , 20 ] and stretchable substrates [ 21 ].…”