The sense of touch is important in our everyday lives and its absence makes it difficult to explore and manipulate everyday objects. Existing online shopping practice lacks the opportunity for physical evaluation, that people often use and value when making product buying decisions. The work described here investigates differential thresholds for simulated frictional surfaces, an important haptic feature for product comparison. One aim is to gain insight into the design space for multiple

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... isons of virtual surfaces as will be needed to support online shopping. A user study has been conducted to explore differential thresholds in stick-slip frictional force. The study demonstrates that, on average, a dynamic friction threshold of 14.1% is needed to differentiate between two frictional surfaces. Moreover, it has shown, for a Phantom Omni, that the maximum number of unique comparable dynamic coefficient of friction combinations available is twenty eight, at any given level of static coefficient of friction. The results are a step towards defining surface differential thresholds for online shopping and other haptic-based applications that require multiple surface comparisons.