The development of printing technologies has enabled the realization of electric circuit fabrication on flexible substrate. However, the current technique remains restricted to single-layer patterning. In this paper, we demonstrate a fully solution-processable patterning approach for multi-layer circuits using a combined method of laser sintering and ablation. Selective laser sintering of silver (Ag) nanoparticle-based ink is applied to make conductive patterns on a heat-sensitive substrate and insulating layer. The laser beam path and irradiation fluence are controlled to create circuit patterns for flexible electronics. Microvia drilling using femtosecond laser through the polyvinylphenol-film insulating layer by laser ablation, as well as sequential coating of Ag ink and laser sintering, achieves an interlayer interconnection between multi-layer circuits. The dimension of microvia is determined by a sophisticated adjustment of laser focal position and intensity. Based on these methods, the flexible electronic circuit with chip-size-package light-emitting diodes was successfully fabricated and demonstrated with functional operations.

Aquaculture is an important source of food for the growing global population. To meet the increasing demand for fish, intensive aquaculture methods are commonly used. However, these methods can lead to stress and disease in fish, which can result in significant economic losses. Gamma-aminobutyric acid (GABA) is a non-protein amino acid that is found in the brain and central nervous system of animals as inhibitory neurotransmitter. It has been shown to have a variety of physiological functions, including stress reduction and immune enhancement. This study investigated the effects of dietary supplementation of GABA on growth, serum biochemistry, innate immunity and disease resistance in juvenile olive flounder (Paralichthys olivaceus) challenged with Edwardsiella tarda under high stocking density. A control diet and three experimental diets were prepared, with 150 mg/kg (GABA150), 200 mg/kg (GABA200), and 250 mg/kg (GABA250) of GABA added to each diet, respectively. The actual GABA content of the experimental diets was analyzed and found to be 63.9 mg/kg (CON), 231.3 mg/kg (GABA150), 291.6 mg/kg (GABA200), and 323.9 mg/kg (GABA250). Each experimental diet was fed to olive flounder with an initial weight of 12.75 g ± 0.3 g in 40 L tanks at two stocking densities: normal density (20 fish/tank) and high density (40 fish/tank). The experiment was conducted in triplicate for each diet and stocking density. The water temperature was maintained at 17.5 ± 1℃ and the salinity at 33 ± 1 ppt. After 8 weeks of feeding trial, growth, feed utilization, whole-body proximate composition, blood analysis, non-specific immune response, and challenge test were performed. There were no significant difference in weight gain and specific growth rate among the GABA concentrations and density × GABA concentration interaction groups. However, the low-density groups showed significantly higher values than the high-density groups (P < 0.05). There was no significant difference in feed efficiency and protein efficiency ratio among all groups. Moreover, there was no significant difference in the whole-body general composition analysis (P > 0.05). In the hematological analysis, there was no significant difference in cortisol in terms of diet and density × GABA concentration interaction, but the high-density experimental group showed a significantly higher value. Blood GABA significantly increased in proportion to the addition amount regardless of the density group (P<0.05). Superoxide dismutase activity in the non-specific immune response showed that the GABA-added experimental group had a significantly higher value than the control group, but there was no significant effect of the density densities or density × GABA concentration interaction (P<0.05). Myeloperoxidase activities in fish fed the GABA200 and GABA250 diets showed significantly higher values, and a density × GABA concentration interaction effect was observed (P<0.05). Lysozyme activity was significantly higher in the GABA150 group than in the CON, GABA200, and GABA250 groups (P < 0.05). After 15 days of challenge test by intraperitoneal injection of Edwardsiella tarda, the cumulative survival rates of the GABA150, GABA200, and GABA250 groups were significantly higher than that of the CON group (P < 0.05). The results suggested that the optimal dietary GABA level for juvenile olive flounder culture is 150 mg/kg, regardless of rearing density, to enhance growth, immune function and disease resistance.

Probiotics play an important role as immunostimulants in improving growth and health status in fish. However, little is known on the effects of probiotics when fish offered a low fish meal diet. This study evaluated the effects of three probiotic bacteria isolated from the fish intestine to replace antibiotics in a reduced fish meal diet fed to the juvenile olive flounder Paralichthys olivaceus. A basal diet without feed additives was used as a control (CON) and five other diets were formulated by supplementation with Bacillus subtilis WB60 (BSWB60) at 1×108 CFU/g, B. subtilis SJ10 (BSSJ10) at 1×108 CFU/g, Enterococcus faecium SH30 (EFSH30) at 1×107 CFU/g, amoxicillin (AMO) at 4 g/kg and oxytetracycline (OTC) at 4 g/kg of the basal diet. Triplicate groups of 25 fish averaging 12.1±0.09 g (mean±SD) were fed one of the six experimental diet groups for 8 weeks. Then, 45 fish from each group were intraperitoneally injected with the pathogenic bacteria, Edwardsiella tarda, and mortality was recorded for 14 days. At the end of the feeding trial, weight gain, specific growth rate and feed efficiency of fish fed the BSWB60 diet were significantly greater than those of fish fed the CON, OTC and AMO diets (P < 0.05). Furthermore, feeding efficiency and protein efficiency ratio of fish fed the BSWB60 diet were significantly greater than those of fish fed the CON, OTC and AMO diets. However, there were no significant differences in survival, hepatosomatic indices, viscerosomatic indices and condition factors among the fish fed the experimental diets. The whole-body proximate composition of the fish was unaffected by the dietary treatments. The serum biochemistry parameters, such as aspartate aminotransferase levels were significantly greater in fish fed the BSSJ10 diet than in those fed the BSWB60 diet. However, serum alanine aminotransferase, glucose and total protein levels were not significantly affected by the experimental diets. The lysozyme activity of fish fed the BSSJ10, BSWB60 and EFSH30 diets was significantly greater than that of the CON, OTC and AMO diets. The myeloperoxidase activity of fish fed the BSWB60 diet was significantly greater than that of the fish fed the CON and AMO diets. The flounder growth hormone levels of fish fed the BSSJ10, BSWB60, EFSH30 and AMO diets were significantly greater than that of the fish fed the CON diet. The interleukin 1β (IL-1β) gene expression levels in fish fed the BSSJ10 and EFSH30 diets were significantly greater than those in fish fed the CON, OTC and AMO diets. The interleukin 10 (IL-10) gene expression levels in fish fed the BSSJ10, BSWB60, EFSH30 and OTC diets were significantly greater than those of fish fed the CON and AMO diets. Intestinal histology revealed that the average villus length of fish fed the BSSJ10, BSWB60, and EFSH30 diets was significantly greater than that of fish fed the CON, OTC and AMO diets. The cumulative survival rates of fish fed the EFSH30 and BSWB60 diets were significantly greater than those of fish fed the CON diet after the 15th day of the challenge test. Overall, the results of the present study demonstrated that the supplementation of autochthonous bacteria, B. subtilis (108 CFU/g diet) or E. faecium (107 CFU/g diet) in the diet could be ideal probiotics to replace antibiotics based on growth performance, the serum biochemical composition, immune responses and disease resistance in olive flounder fed a low fish meal diet..