Income taxes - Net long-term deferred tax liability (Details) - USD ($)	Dec. 31, 2022	Dec. 31, 2021
Deferred tax assets:
Research & development tax credits	$ 58,069	$ 398,413
Loss carry forward	443,076	300,545
Accrued compensation	82,503	112,446
Operating lease liabilities	412,840	469,398
Valuation allowances	(29,036)	(139,207)
Deferred tax assets	967,452	1,141,595
Deferred tax liabilities:
Property and equipment	293,195	254,301
Intangible assets	821,723	982,422
Operating lease right-of-use assets	412,840	469,398
Deferred Tax Liabilities, Gross	1,527,758	1,706,121
Net deferred tax liability	560,306	564,526
Discontinued Operations.
Deferred tax assets:
Operating loss carryforwards - Mexico	5,378,177	4,230,398
Land basis difference - Mexico	2,163,681	1,602,470
Start-up costs - Mexico	4,274,858	4,693,395
Valuation allowances	(11,816,716)	(10,526,263)
Deferred tax assets	$ 0	$ 0