1772
Hierarchical structures such as functional graded materials , structures and surfaces can be produced directly by AM or in combination with other methods .
 engineering feature: Hierarchical structures; material: as; concept or principle: materials; concept or principle: surfaces; material: be; manufacturing process: AM
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:
 engineering feature: Hierarchical structures; material: as; concept or principle: materials; concept or principle: surfaces; material: be; manufacturing process: AM