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.
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...
Advanced design and integration of functioning devices with secured power is of interest for many applications that require complicated, sophisticated, or multifunctional processes in confined environments such as in human bodies. Here, strategies for design and realization are introduced for multifunctional feedback implants with the bifacial design and silicon (Si) photovoltaics in flexible forms. The approaches provide efficient design spaces for flexible Si photovoltaics facing up for sustainable powering and multiple electronic components for feedback functions facing down for sensing, processing, and stimulating in human bodies. The computational and experimental results including in vivo assessments ensure feasibility of the approaches by demonstrating feedback multifunctions, power‐harvesting in milliwatts, and mechanical compatibility for operations in live tissues. This work should useful for wide range of applications that require sustainable power and advanced multifunctions.
Among these, wireless power transfer via RF inductive coupling has the advantage of providing relatively high power. [31,32] However, RF wireless power transfer may have limited efficiency when the transceiver is miniaturized [16,33,34] or misaligned. [28,31] The technology using photovoltaics can also provide adequate electrical power to implants by capturing ambient light [24,36] or capturing light from an external light source. [37,38] While these technological advancements are encouraging, the characteristics of electrical performance when using devices under deformation or misalignment caused by opaque soft skin tissues have not yet been reported. The electrical performance characteristics are essentials in integrating reliable power systems to various electronic implants Herein, we report the electrical performance characteristics of a PV implant and external light source patch depending on misalignment, implantation depth, and deformation, which may occur in practical applications. Our experimental studies included ex vivo trials with a PV implant under an animal skin whose surface was covered by an attachable light source patch. We varied the lateral misalignment distance, implantation depth, and bending radius and direction. These results should be useful in the design and application of wireless power transfer using light for implantable medical electronic devices.
This image demonstrates an ultrathin GaAs solar cell hanging on a thin thread. After coldwelding and epitaxial lift-off processes, the ultrathin GaAs solar cell is transferred on a 1.4 μm thick polymer film substrate. The lightweight and ultra-flexible characteristics of the polymer substrate helps the GaAs solar cell to be applied on unconventional surfaces. More information can be found in article number 2200344 by Jongho Lee and co-workers.
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