Just low strength for the trial.

"Rebecca, just use a little power on it for now."

Rebecca of course obeyed, and it twitched in her palm. She dropped it, and yelped in surprise. Erica caught it, and examined it.

"Huh," she said, "it's not actually much like a vibrator. See?" Erica held out her hand. It was moving, but not the quick vibrations they expected, it was undulating slightly, and pulsing with an artificial heartbeat. It alternated between slightly wider and slightly longer, as if it was trying to thrust itself forward. Then her voice turned eager. "Who gets to test it out?"