Figure 3.

Rendering of a thermal grill interface and infrared images demonstrating patterns of warm and cool temperatures. Drawing (a) is representative of the interface that our group constructed. The top of the interface consists of six copper bars. Each bar is 1.0 cm in length and the bars are spaced 0.15 cm apart. The width of the six-bar interface is 9.8 cm. The electronic components fit inside the labeled compartment next to the fans, which allow for necessary air flow. Each bar is connected to a Peltier device, allowing for programmable temperature control (pink and blue coloring represents bars programmed to warm and cool temperatures, respectively). Infrared images acquired using the device are shown in (b). Left (b) shows all bars set to a cool temperature close to 20.0 °C. Middle (b) shows all bars set to a warm temperature close 40.0 °C. Right (b) shows one bar set at 20.0 °C and another bar near 40.0 °C. The alternating temperature setting is used to produce the pain illusion.