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Existing research has investigated the fatigue properties of 3D printed multi-material specimens and shows that there is a weakness at multi-material interfaces .
 concept or principle: research; machanical property: fatigue; manufacturing process: 3D printed; concept or principle: multi-material interfaces
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: 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} 
 Entities: research, fatigue, 3D printed, multi-material interfaces 
Answer:
 concept or principle: research; machanical property: fatigue; manufacturing process: 3D printed; concept or principle: multi-material interfaces