FlexAura: a flexible near-surface range sensor

The availability of flexible capacitive sensors that can be fitted around mice, smartphones, and pens carries great potential in leveraging grasp as a new interaction modality. Unfortunately, most capacitive sensors only track interaction directly on the surface, making it harder to differentiate among grips and constraining user movements. We present a new optical range sensor design based on high power infrared LEDs and photo-transistors, which can be fabricat-ed on a flexible PCB and wrapped around a wide variety of graspable objects including pens, mice, smartphones, and slates. Our sensor offers a native resolution of 10 dpi with a sensing range of up to 30mm (1.2"") and sampling speed of 50Hz. Based on our prototype wrapped around the barrel of a pen, we present a summary of the characteristics of the sensor and describe the sensor output in several typical pen grips. Our design is versatile enough to apply not only to pens but to a wide variety of graspable objects including smartphones and slates.