Recently, three-dimensional printing (3DP) technology has been widely adopted in biology and biomedical applications, thanks to its capacity to readily construct complex 3D features. Using hot-melt extrusion 3DP, scaffolds for bone tissue engineering were fabricated using a composite of biodegradable polycaprolactone (PCL) and hydroxyapatite (HA). However, there are hardly any published reports on the application of the fused deposition modeling (FDM) method using feed filaments, which is the most common 3D printing method. In this study, we report on the fabrication and characterization of biocompatible filaments made of polycaprolactone (PCL)/hydroxyapatite (HA), a raw material mainly used for bone scaffolds, using FDM 3D printing. A series of filaments with varying HA content, from 5 to 25 wt.%, were fabricated. The mechanical and electrical properties of the various structures, printed using a commercially available 3D printer, were examined. Specifically, mechanical tensile tests were performed on the 3D-printed filaments and specimens. In addition, the electrical dielectric properties of the 3D-printed structures were investigated. Our method facilitates the fabrication of biocompatible structures using FDM-type 3DP, creating not only bone scaffolds but also testbeds for mimicking bone structure that may be useful in various fields of study.

Visible light surveillance cameras are currently deployed on a large scale to prevent crime and accidents in public urban environments. For this reason, various human identification studies using biometric data are underway in surveillance environments. The most active research area is face recognition, which generally shows excellent performance; however, aging, changes in facial expression, and occlusions by accessories cause a rapid decline in recognition performance. To resolve these problems, we propose a periocular recognition method in surveillance environments that is based on the convolutional neural network. In this paper, experiments were performed using the custom-made Dongguk periocular database and the open database of ChokePoint database. It was confirmed that the proposed method performs better than existing techniques used in periocular recognition. It was also found to perform better than conventional techniques in face recognition when an occlusion is present.

In this work, we report on a flexible triboelectric generator (TEG) with a multilayer polymer structure, consisting of a poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) layer sandwiched by polydimethylsiloxane (PDMS) layers for the performance enhancement of TEGs. We confirmed that the output performance of the TEG is closely dependent on the structure and polarization direction of the PVDF-TrFE layer. In addition, the PDMS layer serves as the electron trapping layer and suppresses the discharging of the surface charges, boosting the output performance. Furthermore, the polarized PVDF-TrFE layer in the preferred direction contributes to increasing the surface potential during the contact–separation motion. The interaction between these two polymer layers synergistically leads to the boosted output performance of TEGs. Specifically, the maximum peak-to-peak output voltage and current density of 420 V and 50 μA/cm² generated by the proposed architecture, representing approximately a fivefold improvement compared with the TEG with a single layer, even though the same friction layers were used for contact electrification.

Bio-aerosols are important components of atmospheric aerosols, which can affect human health depending on the origin of biological particles. A real-time monitoring technology for bio-aerosols can rapidly provide information on the current state of biological particles in ambient environment, which substantially minimize the impact of hazardous biological particles. The aim of this study is to evaluate LIF (laser-induced fluorescence) technology on real-time monitoring of bio-aerosols by investigating the correlation between biomaterial concentration (cultured microbes or extracted DNA) and fluorescent particle concentration in ambient environment. For this, we used LIF instrument, BDS (Bio-aerosol Detection System), and analyzed the correlation coefficients from the collected data (the non-fluorescent particle concentration, the fluorescent particle concentration, the cultured microbial concentration, the extracted DNA concentration). Pearson’s correlation coefficients (r) from this study are as follows: 0.85 (p<0.001) between the fluorescent particle concentration and the cultured microbial concentration, 0.93 (p< 0.001) between the fluorescent particle concentration and the extracted DNA concentration, while 0.42 (p<0.01) between the non-fluorescent particle concentration and the cultured microbial concentration, 0.49 (p<0.01) between the non-fluorescent particle concentration and the extracted DNA concentration. It was also found that the size range of the fluorescent particles, which exhibited the highest coefficient for the extracted DNA concentration and the cultured microbial concentration, was 2 to less than 10 micrometer (μm), and their coefficients were 0.89 (p<0.01) and 0.8 (p<0.001), respectively. These results indicate that the fluorescent particles, especially in the range of 2 to less than 10 μm, are highly correlated with bio-aerosols rather than the non-fluorescent particles. Taken together, LIF technology is great for real-time monitoring of bio-aerosols by counting fluorescent particles and resolving particle sizes at ambient atmospheric environment.