I walked into Blackdot’s tattoo studio in Austin’s east side on a sweltering May afternoon. After shaking my sweat-soaked hand, founder and CEO Joel Pennington led me up into an office building and opened the door to a small, three-room space. Critics have unflatteringly compared the studio to a sterile hospital room — a comparison not entirely without merit. In a corner room, the machine I had come here to see loomed: a humming, fridge-sized device reminiscent of an old X-ray unit….