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The ability to design complex copper ( Cu ) parts into the most efficient thermal structures is an old dream , but difficult to realize with conventional manufacturing techniques .
 design, copper, Cu, conventional manufacturing
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:
 design, copper, Cu, conventional manufacturing