This Letter proposes a reliable and lightweight key generator based on a novel bit-self-test arbiter physically unclonable function (BST-APUF). The BST-APUF adds a delay detection circuit into a classical APUF to automatically test the delay deviation that produces each bit of the PUF response and generates a reliability-flag for each response to indicate its reliability. The key generator collects robust responses and produces a secure key using a cryptographic entropy accumulator. FPGA implementation results show that the overhead and the helper data length of the authors proposed key generator are significantly lower than that of the state-of-the-art schemes when generating a 128-bit key with a bit error rate of 10 −9. Notations C i , R i , F i challenge, response, reliability-flag T c delay threshold generated by threshold generator ΔT delay difference between the upper and lower paths ⊙ exclusive-NOR (XNOR) operation MUX, DMUX multiplexer, demultiplexer REG, LFSR, NVM register, linear feedback shift register, non-volatile memory Introduction: Physically unclonable functions (PUFs) promise to be critical hardware primitives that can be used to provide unique identities or produce and store cryptographic keys against tamper attacks for IoT devices [1]. However, PUF outputs are unreliable across environmental variations (voltage and temperature); and thus, cannot be used directly as keys. The error correction code (ECC) mechanisms are required to extract the stable keys from the noise data. However, most of ECC implementations are too expensive for resource-constrained IoT devices with potential safety hazards [2]. In this Letter, we propose an efficient and reliable Arbiter PUF (APUF) using bit self-test strategy and present a reliable and lightweight key generator based on the proposed PUF without using any ECC mechanisms.

Polylactic acid (PLA) has become a popular polymer material due to its superior biocompatibility. At present, there are a few relevant research on heterogeneous bone powder. Besides, the poor dispersibility and adhesivity of inorganic particles in the organic phase remains a problem. In this study, the pork bone powders were modified with N-butanol to improve its dispersibility and compatibility in the PLA matrix. In addition, polybutylene succinate-coterephthalates (PBSA) was applied as a flexibilizer to further reinforce the mechanical properties of materials. The composite filaments with a diameter of 1.75 ± 0.05 mm containing 10 wt% of modified bone powder, 10 wt% PBSA and 80 wt% PLA were prepared by a melt blending method. The obtained results showed that modified particles were uniformly dispersed within the PLA matrix and improved the mechanical properties of the composite filaments with a tensile strength of 48.5 ± 0.2 MPa and a bending strength of 79.1 ± 0.1 MPa and a notch impact strength of 15.8 ± 0.3 kJ/m 2. And the prepared composite materials contained low cytotoxicity, high biocompatibility and printability, which verified the feasibility of it in 3D printing personalized bone repair applications. This provides a theoretical basis for further research on the effect of bone repair in vivo. Therefore, the composite material will have potential applications such as making customized bones and bone scaffolds by three dimensional printing technology.

A new class of multifunctional nanocomposites holds strong potential in three-dimensional (3D) printing. In this study, SrAl 2 O 4 :Eu 2+ ,Dy 3+ powders with fluorescence property were modified with SiO 2 to improve its dispersibility and compatibility in the polylactic acid (PLA) matrix. The composite filaments with a diameter of 1.75 AE 0.05 mm containing 2 wt % of modified particles were prepared by a melt blending method. The fluorescent analysis reveals that the composite filaments can be excited by light with a broad band of wavelength from 345 to 455 nm with the highest excitation intensity at 426 nm and have a major emission peak at 487 nm. The morphological analysis and mechanical performance testing on the printed samples showed that modified particles were uniformly dispersed within the PLA matrix and improved the mechanical properties of the composite filaments. Moreover, the modified particles improved hydrophobic behavior and antibacterial properties in comparison with unmodified composite. Therefore, the composite material will have potential applications such as making prototypes for customized furniture and accessories by 3D printing technology.

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This work aims to investigate dental root filling custom gutta-percha (GP) properties based on melt extrusion 3D printing for periapical periodontal disease treatment. Zinc oxide nanoparticles are incorporated into polyurethane/gutta-percha (PGB) composites. A polyurethane/gutta-percha/ZnO (PGB-Zn) biocomposite including BaSO 4 , polyurethane (PU), GP, and ZnO nanoparticles is designed and fabricated. To improve the dispersion of ZnO nanoparticles, rosin is chosen to modify the surface of the ZnO nanoparticles. The PGB-Zn biocomposite exhibits a maximum tensile strength of 26.795 ± 1.173 MPa and a flexural strength of 6.037 ± 0.37 MPa. The chemical interaction between the nanoparticles and the matrix is found in the physical and mechanical characterization of the polyurethane/gutta-percha/ ZnO (PGB-Zn) biocomposite. The inhibition zone test and absorbance photometry show that the composite material inhibits and kills Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). The CCK-8 experimental results show that the PGB-Zn biocomposite has a cytotoxicity level of 0-I. The obtained PGB-Zn biocomposite in this work can be used for accurate root canal therapy as a filling biocomposite by a fused extrusion method, which effectively decreases the potential risk of the clinical implementation of periapical periodontal disease treatment.