Wouldn’t it be great if, while playing a virtual reality game, you could feel the heat of a fire on your arm? Or the cold of chilly water? Engineers around the world have been trying to make that happen, but there is a big problem: temperature changes are slow. The immersive effect diminishes when the thermal feedback lags behind the virtual cause. That’s why a team from South Korea’s Gwangju Institute of Science and Technology turned to motors to dramatically speed up the process.

The Flip-Pelt wearable device relies on Peltier elements to create heating and cooling effects, which is a common strategy for thermal feedback. Peltier elements use electricity to produce thermal transfer, heating one side of the element while simultaneously cooling the other side. By placing a Peltier element against the skin, it is possible to create a cooling or heating sensation on demand.

But it takes a long time to reverse the thermal transfer — changing a side of the Peltier element from hot to cold is too slow to be useful for VR thermal feedback. So, the Flip-Pelt prototype doesn’t even bother. Instead, it keeps the Peltier elements going in just one direction and physically swaps the side of the elements that touch the user’s skin.

The prototype Flip-Pelt device contains eight Peltier elements arranged in two rows along the inside of the user’s forearm. Eight servo motors, controlled by an Arduino Nano 33 IoT board, can flip the elements from the cool side to the hot side in response to events in the VR world. The Arduino also controls the Peltier elements themselves through H-bridges, so it can adjust the power going to each.

While this is relatively complex, it does create almost instant changes in perceived temperature.

You can read more about the project in the team’s published paper here.

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Imagine playing Half-Life: Alyx and feeling the gun heat up in your hand as you take down The Combine. Or operating a robot through augmented reality and feeling coldness on your fingers when you get close to exceeding the robot’s limits. A prototype device called ThermoGrasp brings that thermal feedback to the mixed reality applications.

ThermoGrasp is a wearable thermal feedback system designed for virtual reality and augmented reality, created by Arshad Nasser and Khalad Hasan of the University of British Columbia. It consists of thermoelectric modules attached to the user’s fingers with Velcro straps. Those are capable of creating thermal sensations — both warm and cold — in response to what happens in the virtual world. Those sensations can relate to any condition or event that the developer chooses, whether for immersion or utility.

Nasser and Hasan built the prototype using an Arduino Mega 2560 board, which controls the thermoelectric modules through custom H-bridge drivers. Those thermoelectric modules are Peltier devices, which are normally associated with cooling. They can create a cooling feeling on the skin, but can also do the opposite and produce a warm feeling. The Arduino controls the drivers through pulse-width modulation (PWM), allowing for granular adjustment. The thermoelectric modules are capable of changing temperature at a rate of 3.5°C per second and so can produce a noticeable sensation within just a couple of seconds.

In testing, users found that cool sensations were easier to detect than warm sensations, but that both were useful and increased immersion.

Image credit: A. Nasser et al.

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