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Designing metallic cellular structures with triply periodic minimal surface ( TPMS ) sheet cores is a novel approach for lightweight and multi-functional structural applications .
 metallic, cellular structures, triply periodic minimal surface, sheet, cores, lightweight
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: manufacturing standard, machanical property, manufacturing process, material, engineering feature, process parameter, machine or equipment, application, process characterization, enabling technology, biomedical, concept or principle 
Text: {0} 
Answer:
 metallic, cellular structures, triply periodic minimal surface, sheet, cores, lightweight