Accounts Receivable, net - Allowance for doubtful accounts (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Accounts Receivable, net
Balance at beginning of year	$ (151,459)	$ (170,038)
Provision for doubtful accounts	(54,913)	(146,916)
Amounts written off	22,643	165,495
Balance at end of year	$ (183,729)	$ (151,459)