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Fieldint and colleagues face several challenges to adapt and optimize the processing parameters to produce scaffolds using a 3D binder jetting printer and commercially available binders .
 concept or principle: face; concept or principle: parameters; engineering feature: scaffolds; machine or equipment: 3D binder jetting printer; material: binders
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: face; concept or principle: parameters; engineering feature: scaffolds; machine or equipment: 3D binder jetting printer; material: binders