Intangible assets, net consisted of the following:

 

  

At December 31, 2018 and 2017, the Company had capitalized approximately $354,427 and $330,070, respectively, for costs related to patents that have not been awarded. During the years ended December 31, 2018 and 2017, the Company wrote-off $56,504 and $87,655, respectively, in previously capitalized patent costs.

 

Amortization expense amounted to $64,981 and $51,732 for the years ended December 31, 2018 and 2017, respectively. Amortization expense for the succeeding five years and thereafter is $65,787 (2019-2023) and $713,047 (thereafter).