Soft and Compliant Contact-Rich Hair Manipulation and Care
Overview
MOE-Hair: A soft robotic system for safe and effective hair care
Abstract
Hair care robots have the potential to alleviate labor shortages in elderly care and enable those with limited mobility to express their identities through hair styling. We present MOE-Hair, a system that incorporates a compliant soft robotic manipulator and visual method for applied force estimation to perform three hair-care skills: head patting, finger combing, and hair grasping. MOE-Hair underscores two advantages of soft robotic manipulators in hair-care applications: safety through mechanical compliance and sensing force through observing deformation.
Key Findings
Safety Through Compliance
MOE soft robot hand applies 74% less force than rigid grippers while grasping comparable amounts of hair, demonstrating that soft robots can provide more comfortable care without sacrificing effectiveness.
Visual Force Estimation
Our novel force estimation module combines visual deformation data with tendon tensions to precisely track applied forces, reducing sensing errors by up to 60% compared to actuator-only approaches.
User Preference
Our study with 12 participants showed statistically significant preference for MOE with force estimation across all tasks. Participants commented the system felt "really similar to human fingers" and provided a sensation "like a head massage."
MOE: Multi-finger Omnidirectional End-effector
We introduce a dexterous tendon-driven soft robot manipulator that we call Multi-finger Omnidirectional End-effector (MOE) for hair-care applications.
Design Features:
- Soft Fingers: Molded from low-hardness silicone (Ecoflex 00-30) for gentle contact
- Tendon-Driven System: Two servomotors activate each finger through four embedded tendons
- Wrist-Mounted Camera: RGBD camera provides egocentric view for force estimation
- Human-Like Form Factor: 105mm length, 17mm diameter fingers designed for intuitive interaction
The design addresses a key challenge in previous works where human subjects tend to perceive rigid robots as being "rough" during hair care tasks. MOE's compliance makes it safer in unstructured environments and more robust in contact-rich manipulation tasks.
Hair Care Skills
Head Patting
MOE approaches the user's head from either the top or side to pat it, providing gentle contact with consistent force. The compliance of the fingers ensures safety during this interaction.
This task demonstrates MOE's ability to make initial contact with the head in a controlled, comfortable manner.
Finger Combing
MOE follows a user-defined trajectory across the user's head for finger combing, maintaining consistent contact with the scalp even as it moves along a path.
This task showcases the system's ability to maintain proper contact force during continuous movement, adapting to the contours of the head.
Hair Grasping
MOE approaches the user's head from either the top or side and grasps hair from near the scalp. The soft fingers allow for effective grasping while applying minimal force to the head.
In our tests, MOE applied 74% less force than rigid grippers while still grasping a comparable amount of hair.
Force Estimation Module
To enable MOE to maintain contact with the head during tasks and perform tasks effectively and comfortably for users, we developed methods for predicting MOE contact forces using:
- Visual Deformation: Using the wrist-mounted egocentric RGBD camera to capture depth images of MOE as it deforms during contact
- Tendon Tension: Observing the actuator current load which correlates to tension on the tendons
Our evaluation shows that the combined approach reduces sensing errors by up to 60.1% compared to actuator current load-only and 25.4% compared to depth image-only baselines.
User Study
We conducted a user study with 12 participants with diverse hair types to evaluate MOE-Hair across three key dimensions:
Task Effectiveness
Participants rated MOE-Hair as significantly more effective than the vision-only baseline across all three tasks.
User Comfort
Participants reported higher comfort levels, particularly in the more involved hair-grasping task.
Appropriate Use of Force
Significant preference for MOE-Hair's force application, especially during finger combing.
Participant Feedback:
"It felt really similar to human fingers... I kind of forgot it was a robot arm for a minute."
"It was like a head massage."
"I felt really comfortable."
Future Work & Extensions
We're extending MOE to various dexterity projects including:
- Dynamic pen spinning (arxiv.org/abs/2411.12734)
- Learning in-hand manipulation from demonstration (arxiv.org/abs/2503.01078)
- Additional hair care tasks including brushing and styling
- Applications for elderly and mobility-impaired users
This work demonstrates the unique advantages of soft robots in contact-rich hair-care tasks, while highlighting the importance of precise force control despite the inherent compliance of the system.
Citation
@inproceedings{yoo2025moehair,
title={Soft and Compliant Contact-Rich Hair Manipulation and Care},
author={Yoo, Uksang and Dennler, Nathaniel and Xing, Eliot and Mataric, Maja and Nikolaidis, Stefanos and Ichnowski, Jeffrey and Oh, Jean},
booktitle={Proceedings of the 2025 ACM/IEEE International Conference on Human-Robot Interaction},
year={2025}
}Acknowledgements
This work is supported by the NSF GRFP (Grant No. DGE2140739) and MOTIE, Korea (Grant No. 20018112).