9018
Over the past two decades , additive manufacturing has opened a new window of opportunities in fabricating complex porous matrix structures such as cellular solids .
 additive manufacturing, fabricating, porous, as
Please list all entity words in the text that fit the category. Output format is "word1, 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:
 additive manufacturing, fabricating, porous, as