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The results show that 3D printing can provide a simple and practical method for implementing phononic crystal concepts with minimal modification of the host structure .
 manufacturing process: 3D printing; manufacturing process: simple; concept or principle: structure
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: 3D printing, simple, structure 
Answer:
 manufacturing process: 3D printing; manufacturing process: simple; concept or principle: structure