3D printing of liquid metal remains a big challenge due to its low viscosity and large surface tension. In this study, we use Carbopol hydrogel and liquid gallium-indium alloy to prepare a liquid metal high internal phase emulsion gel ink, which can be used for direct-ink-writing 3D printing. The high volume fraction (up to 82.5%) of the liquid metal dispersed phase gives the ink excellent elastic properties, while the Carbopol hydrogel, as the continuous phase, provides lubrication for the liquid metal droplets, ensuring smooth flow of the ink during shear extrusion. These enable high-resolution and shape-stable 3D printing of three-dimensional structures. Moreover, the liquid metal droplets exhibit an electrocapillary phenomenon in the Carbopol hydrogel, which allows for demulsification by an electric field and enables electrical connectivity between droplets. We have also achieved the printing of ink on flexible, non-planar structures, and demonstrated the potential for alternating printing with various materials.

3D printing of liquid metal remains a big challenge due to its low viscosity and large surface tension. In this study, we use Carbopol hydrogel and liquid gallium-indium alloy to prepare a liquid metal high internal phase emulsion gel ink, which can be used for direct-ink-writing 3D printing. The high volume fraction (up to 82.5%) of the liquid metal dispersed phase gives the ink excellent elastic properties, while the Carbopol hydrogel, as the continuous phase, provides lubrication for the liquid metal droplets, ensuring smooth flow of the ink during shear extrusion. These enable high-resolution and shape-stable 3D printing of three-dimensional structures. Moreover, the liquid metal droplets exhibit an electrocapillary phenomenon in the Carbopol hydrogel, which allows for demulsification by an electric field and enables electrical connectivity between droplets. We have also achieved the printing of ink on flexible, non-planar structures, and demonstrated the potential for alternating printing with various materials.

Yucha is a home-made, fermented fish product in South China. The quality of yucha can vary depending on environmental factors. In order to determine the effects of temperature on bacterial biodiversity and quality of fermented yucha products, in the present study, yucha was fermented at 15°C, 20°C, 25°C, and 30°C. Bacterial cells in all yucha samples grew from 3.7 log CFU/g at the onset of the fermentation and reached growth over 7.0 log CFU/g within 1 week. Lactobacillus plantarum was predominated in the 20°C and 25°C fermented yucha products, while Lactobacillus sakei and Lactobacillus brevis were the most abundant in the yucha products fermented at 15°C and 30°C, respectively. Predominant bacterial species are presumed to be potential starters to drive yucha fermentation. Evaluation of yucha qualities demonstrated that lower biogenic amine contents, better texture properties, and more desirable volatile compounds were identified in yucha products fermented at 20°C. Therefore, this temperature is recommended for industrial yucha processing in the future.

Yucha is a home-made, fermented fish product in South China. The quality of yucha can vary depending on environmental factors. In order to determine the effects of temperature on bacterial biodiversity and quality of fermented yucha products, in the present study, yucha was fermented at 15°C, 20°C, 25°C, and 30°C. Bacterial cells in all yucha samples grew from 3.7 log CFU/g at the onset of the fermentation and reached growth over 7.0 log CFU/g within 1 week. Lactobacillus plantarum was predominated in the 20°C and 25°C fermented yucha products, while Lactobacillus sakei and Lactobacillus brevis were the most abundant in the yucha products fermented at 15°C and 30°C, respectively. Predominant bacterial species are presumed to be potential starters to drive yucha fermentation. Evaluation of yucha qualities demonstrated that lower biogenic amine contents, better texture properties, and more desirable volatile compounds were identified in yucha products fermented at 20°C. Therefore, this temperature is recommended for industrial yucha processing in the future.

Additional file 6: Table S6. Metabolites detected in sample “P0” and “F3”.

Additional file 6: Table S6. Metabolites detected in sample “P0” and “F3”.

Additional file 4: Table S4. Differentially expressed proteins between “P0” and “F3”.

Additional file 3: Table S3. Differentially expressed genes between “P0” and “F3”.

Additional file 3: Table S3. Differentially expressed genes between “P0” and “F3”.

Additional file 4: Table S4. Differentially expressed proteins between “P0” and “F3”.