My future work par3

 The other day, I introduced the molecular machine. Here, I will explain mechanism of molecular machine, chemical affinity and steric obstacle. 
 First, chemical affinity is attraction and repulsion between different atoms. Each atom has electronegativity, so molecules have dipolar. This dipolar interacts with another molecular one. Chemists take advantage of this affinity and make functional molecules.
 In the following article, I will explain steric obstacle. 
 See you.