6781
The relatively low impedance of the copper-based filament enabled its use for 3D printing of a receiver coil for wireless power transfer .
 filament, 3D printing, power
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:
 filament, 3D printing, power