He "acquired" Options to buy, not stock. And he could have been given these by the company instead of outright pay. In short, the statement "The CTO just bought 50k" is completely inaccurate.
This is nothing more than a gamble by him.
If there were major events happening you would have every insider/board member snapping up shares.
But alas, Sigma labs sits here, another day with zero news/events/sales. And another day closer to taking their happy arses back to where they belong. The OTC, perpetual dilutive, dump countless shares market.