7657
The magnetic ink allows for the fabrication of multi-material structures such as hydrogels with a magnetic nanoparticle gradient .
 ink, fabrication, multi-material structures, 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:
 ink, fabrication, multi-material structures, as