Human–robot creative collaboration is often constrained by command–response paradigms that position robots as tools rather than partners. While expressive robotics has shown social values, its role and behaviors in shaping creative partnerships with humans remains underexplored. Therefore, we investigate how robots’ expressive behaviors influence co-creative engagement. In a formative study with 5 participants, we identified design insights for users to perceive a robot arm’s expressive behaviors. We then implemented these expressive behaviors and conducted a within-subject study with 18 participants, comparing functional-only and expressive conditions in figure drawing tasks. Results showed that expressive behaviors significantly enhanced human-robot collaboration where they shifted from viewing the robot as a tool to a partner with a stronger emotional connection and collaborative satisfaction. Our contributions include empirical evidence of partnership transformation and design insights for facilitating human-robot creative collaboration.

The dental plaque disclosing agent helps guide plaque removal by revealing plaque on the teeth. However, existing toothbrushes cannot provide visualization of the stained plaque beneath the toothpaste foam during brushing. To fill this gap, this paper proposes PIT and uses smartphone to provide real-time plaque visualization during brushing. PIT introduces novel hardware, including a micro camera, four green LEDs, and a mechanical structure, offering a stable camera view of bristle position and bristle rotation. To address the challenge of toothpaste foam obstruction, we derived an optical channel model that guided the design of the light source to enhance plaque visibility. Furthermore, we designed a deep neural network specifically for plaque segmentation under thick foam. Finally, the trained distilled student model was run on a smartphone and evaluated on both denture models and human subjects. The results show that PIT achieved an IoU (Intersection over Union) of 75.22% and a latency of 29 ms, with robust performance across various conditions. Evaluation by 10 participants revealed that PIT helped reduce plaque coverage to 5.6% within two minutes of brushing, significantly outperforming existing advanced toothbrushes.