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Furthermore , the authors verified that this design tool can be applied to practical structures by designing , printing and testing a gradient index flat lens .
 engineering feature: design; material: be; process characterization: testing; manufacturing process: lens
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: design, be, testing, lens 
Answer:
 engineering feature: design; material: be; process characterization: testing; manufacturing process: lens