1947
One can foresee that if some work in the future can help realize multi-material topology optimization for 3D metal structures , then the complexity capability of AM can be further explored not only for lightweight design but also for a combined multi-function design .
 concept or principle: multi-material; concept or principle: optimization; engineering feature: 3D metal structures; concept or principle: complexity; manufacturing process: AM; material: be; concept or principle: lightweight; engineering feature: design; engineering feature: multi-function design
Please list all entity words in the text that fit the category.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} 
Answer:
 concept or principle: multi-material; concept or principle: optimization; engineering feature: 3D metal structures; concept or principle: complexity; manufacturing process: AM; material: be; concept or principle: lightweight; engineering feature: design; engineering feature: multi-function design