Abstract There is an unmet need for developing a new class of smart medical implants with novel properties and advanced functionalities. Here, the concept of “self‐aware implants” is proposed to enable the creation of a new generation of multifunctional metamaterial implantable devices capable of responding to their environment, empowering themselves, and self‐monitoring their condition. These functionalities are achieved via integrating nano energy harvesting and mechanical metamaterial design paradigms. Various aspects of the proposed concept are highlighted by developing proof‐of‐concept interbody spinal fusion cage implants with self‐sensing, self‐powering, and mechanical tunability features. Bench‐top testing is performed using synthetic biomimetic and human cadaver spine models to evaluate the electrical and mechanical performance of the developed patient‐specific metamaterial implants. The results show that the self‐aware cage implants can diagnose bone healing process using the voltage signals generated internally through their built‐in contact‐electrification mechanisms. The voltage and current generated by the implants under the axial compression forces of the spine models reach 9.2 V and 4.9 nA, respectively. The metamaterial implants can serve as triboelectric nanogenerators to empower low‐power electronics. The capacity of the proposed technology to revolutionize the landscape of implantable devices and to achieve better surgical outcomes is further discussed.
Gold−silver alloy nanoparticles with varying mole fractions are prepared in aqueous solution by the co-reduction of chlorauric acid HAuCl4 and silver nitrate AgNO3 with sodium citrate. As the optical absorption spectra of their solutions show only one plasmon absorption it is concluded that mixing of gold and silver leads to a homogeneous formation of alloy nanoparticles. The maximum of the plasmon band blue-shifts linearly with increasing silver content. This fact cannot be explained by a simple linear combination of the dielectric constants of gold and silver within the Mie theory. On the other hand, the extinction coefficient is found to decrease exponentially rather than linearly with increasing gold mole fraction xAu. Furthermore, the size distribution of the alloy nanoparticles is examined using transmission electron microscopy (TEM). High-resolution TEM (HRTEM) also confirms the formation of homogeneous gold−silver alloy nanocrystals.
Regulation of charge-transport direction is realized through the coupling of triboelectrification, electrostatic induction, and semiconducting properties for area-scalable conversion of mechanical energy. The output current from each unit triboelectric generator can always constructively add up due to the unidirectional flow of electrons. This work proposes a practical and general route to area-scalable applications of the triboelectric generator and other energy-harvesting techniques.
The fine structure of the wing scale of a Morpho Peleides butterfly was examined carefully, and the entire configuration was completely replicated by a uniform Al2O3 coating through a low-temperature ALD process. An inverted structure was achieved by removing the butterfly wing template at high temperature, forming a polycrystalline Al2O3 shell structure with precisely controlled thickness. Other than the copy of the morphology of the structure, the optical property, such as the existence of PBG, was also inherited by the alumina replica. Reflection peaks at the violet/blue range were detected on both original wings and their replica, while a simple alumina coating shifted the reflection peak to longer wavelength because of the change of periodicity and refraction index. The alumina replicas also exhibited similar functional structures as waveguide and beam splitter, which may be used as the building blocks for photonic ICs with high reproducibility and lower fabrication cost compared to traditional lithography techniques.
