541
Altogether , we demonstrated that the microneedle arrays can be fabricated through a simple single - step process and needles were mechanically strong to penetrate skin , increasing the permeability of encapsulated drug through skin .
 None
Given options, please tell me the categories of all the listed entity words.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
 Entities:  
Answer:
 None