Towards Accessible Mobility Support: User-Centered Design of a Passive, Multi-Functional, Low-Cost Knee Exoskeleton (CHI'26)

Yuyu Lin, Yujia Liu, Emma Kim, Alexandra Ion

Abstract: Walking aids are critical for people with mobility impairments, yet current options remain unsatisfactory. Static knee braces are lightweight and affordable, but their rigid joints force users into unnatural gait patterns, leading to fatigue, reduced safety, and high abandonment rates. Robotic exoskeletons, in contrast, offer dynamic assistance that adapts to gait phases but rely on sensors, motors, and batteries that make them heavy, complex, and prohibitively expensive. In this paper, we propose a fully passive knee exoskeleton design that combines the accessibility of static braces with the adaptive functionality of robotic systems. Our design employs a mechanical trigger under the foot to lock and release the knee joint in sync with the gait cycle, enabling more natural walking without electronics or actuation. Using human-centered methods, we conducted interviews with clinicians and orthosis users to guide our design and evaluated an early prototype as a design probe with stakeholders.

Project Page | DOI | Video | Preview | CMU SCS News

Personalized Bistable Orthoses for Rehabilitation of Finger Joints (UIST'25)

Yuyu Lin, Dian Zhu, Anoushka Naidu, Kenneth Yu, Deon Harper, Eni Halilaj, Douglas Weber, Deborah Ellen Kenney, Adam J. Popchak, Mark Baratz, Alexandra Ion

Best Demo Honorable Mention (Jury's Choice)

Abstract: Orthoses are essential components of rehabilitation, yet limited in functionality. Static braces immobilize joints, which, especially for hand and finger injuries, interfere with users' daily activities. Additionally, early mobilization schedules require users to take off and reapply their static orthoses frequently, which is cumbersome. To facilitate both rehabilitation and dexterity, we introduce a novel multifunctional yet unpowered finger orthosis design. Our design supports easy switching between two distinct states: a stiff state for immobilization and a flexible state for mobilization. A key benefit is that it can be customized using our computational design tool, and 3D printed in one piece. Our computational design pipeline supports tailoring the switching thresholds of the brace based on patients' individual finger strengths and range of motion. Following a preliminary study with 10 healthy people that validates the usability and wearability of the brace, our two-week case study with a patient indicates that our brace supports everyday activities and assists with rehabilitation.

Project Page | DOI | Video | Preview | CMU SCS News

Wearable Material Properties: Passive Wearable Microstructures as Adaptable Interfaces for the Physical Environment (CHI'25)

Yuyu Lin, Hatice Gokcen Guner, Jianzhe Gu, Sonia Prashant, Alexandra Ion

Abstract: Users interact with static objects daily, but their preferences and needs may vary. Making the objects dynamic or adaptable requires updating all objects. Instead, we propose a novel wearable interface that empowers users to adjust perceived material properties. To explore such wearable interfaces, we design unit cell structures that can be tiled to create surfaces with switchable properties. Each unit can be switched between two states while worn, through an integrated bistable spring and tendon-driven trigger mechanism. Our switchable properties include stiffness, height, shape, texture, and their combinations. Our wearable material interfaces are passive, 3D printed, and personalizable. We present a design tool to support users in designing their customized wearable material properties. We demonstrate several example prototypes, e.g., a sleeve allowing users to adapt to how different surfaces feel, a shoe sole for users walking on different ground conditions, a prototype supporting both pillow and protective helmet properties, or a collar that can be transformed into a neck pillow with variable support.

Project Page | DOI | Video | Preview

ConeAct: A Multistable Actuator for Dynamic Materials (CHI'24)

Yuyu Lin, Jesse T. Gonzalez, Zhitong Cui, Yash Rajeev Banka, Alexandra Ion

Abstract: Complex actuators in a small form factor are essential for dynamic interfaces. In this paper, we propose ConeAct, a cone-shaped actuator that can extend, contract, and bend in multiple directions to support rich expression in dynamic materials. A key benefit of our actuator is that it is self-contained and portable as the whole system. We designed our actuator’s structure to be multistable to hold its shape passively, while we control its transition between states using active materials, i.e., shape memory alloys. We present the design space by showcasing our actuator module as part of self-rolling robots, reconfigurable deployable structures, volumetric shape-changing objects and tactile displays. To assist users in designing such structures, we present an interactive editor including simulation to design such interactive capabilities.

Project Page | DOI | Video | Preview