Recent advances in soft materials and mechanics activate development of many new types of electrical medical implants. Electronic implants that provide exceptional functions, however, usually require more electrical power, resulting in shorter period of usages although many approaches have been suggested to harvest electrical power in human bodies by resolving the issues related to power density, biocompatibility, tissue damage, and others. Here, we report an active photonic power transfer approach at the level of a full system to secure sustainable electrical power in human bodies. The active photonic power transfer system consists of a pair of the skin-attachable photon source patch and the photovoltaic device array integrated in a flexible medical implant. The skin-attachable patch actively emits photons that can penetrate through live tissues to be captured by the photovoltaic devices in a medical implant. The wireless power transfer system is very simple, e.g., active power transfer in direct current (DC) to DC without extra circuits, and can be used for implantable medical electronics regardless of weather, covering by clothes, in indoor or outdoor at day and night. We demonstrate feasibility of the approach by presenting thermal and mechanical compatibility with soft live tissues while generating enough electrical power in live bodies through in vivo animal experiments. We expect that the results enable long-term use of currently available implants in addition to accelerating emerging types of electrical implants that require higher power to provide diverse convenient diagnostic and therapeutic functions in human bodies.

Implantable electronics in soft and flexible forms can reduce undesired outcomes such as irritations and chronic damages to surrounding biological tissues due to the improved mechanical compatibility with soft tissues. However, the same mechanical flexibility also makes it difficult to insert such implants through the skin because of reduced stiffness. In this paper, a flexible-device injector that enables the subcutaneous implantation of flexible medical electronics is reported. The injector consists of a customized blade at the tip and a microflap array which holds the flexible implant while the injector penetrates through soft tissues. The microflap array eliminates the need of additional materials such as adhesives that require an extended period to release a flexible medical electronic implant from an injector inside the skin. The mechanical properties of the injection system during the insertion process are experimentally characterized, and the injection of a flexible optical pulse sensor and electrocardiogram sensor is successfully demonstrated in vivo in live pig animal models to establish the practical feasibility of the concept.

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of the implanted devices induces minimized inflammation on live tissues, thus improves long-term stability, [14,[19][20][21] the insufficient bending rigidity can make manipulation of the flexible devices difficult, especially in implantation procedures, requiring relatively large incision to settle flexible devices.Recently, many approaches for minimally invasive implantation of flexible devices into bodies were investigated, particularly for biomedical implants including the flexible neural probes [22] and other silicon electronics. [7,23] One approach is to increase mechanical stiffness temporarily by coating bioresorbable materials over the flexible devices to insert through an incision without buckling. [24][25][26] The devices recover the original flexibility by dissolving the supporting materials after implantation. Other groups use stiff temporary guides to support flexible electronic devices while reaching into target organs. The guides include the stiff shank mounting the sheath-type devices, [27] the microflap array to switch adhesion on the metal substrate, [28] and the syringe to inject the mesh shape electronics. [29] Although some of these methods without using bioresorbable materials enable immediate release of devices, deliberate external manipulation is required to control adhesion or types of implantable devices may be limited to pass through submillimeter needles. When using bioresorbable materials as supporting structures, they may need to be thick enough to have sufficient mechanical stiffness to penetrate through live tissues [30,31] even though it may take much dissolution time to completely dissolve before starting functioning such as reading biological signals in live bodies.In many cases, bioresorbable materials such as self-assembled monolayer coating, [32] polyethylene glycol, [33] sacrificial metal, [34] and silk fibroin [35] temporarily hold the flexible devices on the stiff guides while inserting. The procedures require waiting time for the biomaterials to dissolve to release flexible devices from the temporary stiff guides that are to be retracted from bodies. It will be very convenient to short the dissolution time for both surgeons and patients under operations. Here, we present the insertion shuttle that temporarily holds a flexible implantable device while inserting and releases the device by dissolving the adhesive layer with the aid of liquid delivered more efficiently to the interface through the elastomeric post array and microfluidic channel constituted on the customized stiff metal substrate. The insertion shuttle we report here has advantages of using a stiff guide for more convenient handling Implantable biomedical devices in flexible forms are attractive as they are more mechanically compatible with soft live tissues than rigid implants. The flexible implants can bend comfortably instead of delivering stress or strain to the surrounding live tissues when they are exposed to external stresses. However, because of the nature of the mechanical properties, the flexible bi...

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