Lab Data and Lived Experience: How User Testing Shaped the ProHensor

By Marins Inc.

Why user insight is the first instrument

Engineering intuition suggested a simple approach to finger grip. Add more rubber, improve friction, call it done. Real-life use revealed a different truth. A rubber sleeve concept increased grip during tests, but in a pocket it grabbed fabric and blocked access to a phone. The solution was targeted rubber placement that supports grip without pocket snagging. Root3 Labs

Seeing inside the mechanism to understand feel

To trace force paths and interactions, the team literally opened windows into the prototype. Viewing holes were drilled so engineers could watch components under a microscope and connect what users felt to what the mechanism was doing. This helped separate what was modeled from true design intent. Root3 Labs

Two-week trials, real tasks, honest feedback

Darryl took prototypes home for two-week stretches and used them for the kinds of things you cannot fully script in a lab. Opening bags of chips, crushing cans, hauling groceries, biking, and home projects all produced practical feedback that guided changes quickly. Root3 Labs

Bench data that compresses a lifetime of use

User feedback points to what matters. Bench testing proves it at speed. A University of Delaware rig allowed the team to simulate a device’s life in just under 700 actuations at roughly five seconds per cycle. That provided a high confidence check on function and wear in about an hour, which is powerful for setting maintenance expectations and warranty rules. Root3 Labs

The loop that reduces surprises

Real-world trials inform hypotheses. Benchtop cycles validate them quickly. Manufacturing drawings translate that knowledge into repeatable parts. Working this loop improves comfort and control, reduces unplanned service, and helps align with payor preferences through clear maintenance and performance data.

What this approach means for clinicians

• More predictable performance in daily tasks that matter to patients

• Data to plan proactive follow-ups and maintenance windows

• Documentation that supports conversations with payors and care teams

What this approach means for users

• Confidence that grips feel natural in real clothing and real pockets

• Control that is consistent and repeatable across tasks

• Uptime and reliability that support independence at work and home

Thanks to our engineering partner

We developed ProHensor with Root3 Labs using a test, learn, and validate approach. For details on the pocket-snag discovery, microscope viewing, real-life trials, and cycle testing, see their case study: User Centered Product Design, Mechanical Prosthetic Development with Marins, Inc. Root3 Labs