Human-centered Intelligent Systems Lab

Smartphone use in crowded public spaces exposes users to shoulder surfing, allowing nearby bystanders to easily access privacy-sensitive information on the screen. We present Fold2Unfold, a screen privacy protection system for foldable smartphones that ensures screen content readable only from the user's viewpoint without additional hardware. Fold2Unfold decomposes the original content into two complementary, individually illegible shares displayed across screens, and leverages inter-screen reflection to reconstruct the content. By tracking the user's eye position and dynamically warping the content accordingly, the system ensures that the reconstructed content is readable only to the user. We implement Fold2Unfold on a commercial foldable device and evaluate its usability and security through controlled user studies involving a PIN entry task. Our results show that Fold2Unfold substantially reduces information leakage under shoulder surfing, with attackers inferring only 6.5% shown on a 10-digit keypad, while incurring a modest input time increase compared to our baseline keypad. Capillary Refill Time (CRT) refers to the time required for the skin to recover its color after pressure temporarily restricts blood flow and is then released. CRT is widely used in clinical settings as an indicator of peripheral perfusion and circulatory status, particularly in conditions such as dehydration, sepsis, shock, and hypothermia. Despite its potentials for versatile and accessible everyday health screening, CRT assessment is mostly confined to clinical settings, and extending it to everyday life introduces nontrivial challenges. We present CapWear, a footwear-based system that continuously estimates capillary refill dynamics during everyday walking. CapWear leverages the natural he