8042
Microfluidic biochips integrated using the substrates with arrays of nanowires and polydimethylsiloxane channels have been demonstrated to be effective for detecting antigens , and a detection limit of antigens at 0 . 2 mu g mL ( - 1 ) has been achieved , which is improved by a factor of 50 compared to that based on flat substrates without the nanowires .
 polydimethylsiloxane
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 polydimethylsiloxane