StimulHeat: a low-energy wearable thermal feedback device using Peltier elements with heat flow controlled loop for hand interactions in virtual reality.

Nowadays, the majority of wearable thermal feedback systems designed for use in virtual reality applications are not compatible or not integrated to standard controllers and are based on temperature control. The objectives of the present work are to enable integration with existing controllers, in this case Valve Index controllers, and to propose an alternative approach to managing thermal stimulation with Peltier modules by controlling heat flow instead of temperature. We introduce StimulHeat as a wireless, low power thermal feedback system, based on the continuous relationship between heat and current injection in thermoelectric device (TED). First, we designed an optimized TED driver capable of injecting a continuous, bidirectional current into the TED, thereby driving it as a heater or cooler. Subsequently, this driver was implemented in an electronic board to include temperature and heat flow control loops, as well as Bluetooth Low Energy interface for remote control. A mechanical integration was conducted, in the form of a controller extension which is non-intrusive and can be clipped to Valve Index controllers to enclose the TED, temperature sensors and electronics. Finally, we present a supplementary user study validating StimulHeat for use in Virtual Reality for short-duration thermal contact sensation, utilizing a Unity-built virtual environment with our open-source package.