Kiri-Spoon: A Kirigami Utensil for Robot-Assisted Feeding

TL;DR

Kiri-Spoon introduces a kirigami-based, spoon-like utensil designed for robot-assisted feeding that can encapsulate diverse morsels to simplify acquisition, carry, and transfer. Through stakeholder-driven design, a physics-based mechanics model, and three experimental threads (autonomous acquisition, disability user studies, and able-bodied user studies), the work demonstrates a mechanical advantage over traditional utensils and complementary gains from modern autonomous algorithms. The results show that a single utensil can function as both fork and spoon, enabling orientation-invariant grasping and improved handling of soft, slippery, and small foods, with overall positive user perceptions despite some comfort trade-offs. The study argues for a practical path toward more usable robot-assisted feeding systems by integrating mechanical intelligence with algorithmic advances, while outlining limitations (e.g., difficulty with large, flat foods) and directions for future improvements.

Abstract

For millions of adults with mobility limitations, eating meals is a daily challenge. A variety of robotic systems have been developed to address this societal need. Unfortunately, end-user adoption of robot-assisted feeding is limited, in part because existing devices are unable to seamlessly grasp, manipulate, and feed diverse foods. Recent works seek to address this issue by creating new algorithms for food acquisition and bite transfer. In parallel to these algorithmic developments, however, we hypothesize that mechanical intelligence will make it fundamentally easier for robot arms to feed humans. We therefore propose Kiri-Spoon, a soft utensil specifically designed for robot-assisted feeding. Kiri-Spoon consists of a spoon-shaped kirigami structure: when actuated, the kirigami sheet deforms into a bowl of increasing curvature. Robot arms equipped with Kiri-Spoon can leverage the kirigami structure to wrap-around morsels during acquisition, contain those items as the robot moves, and then compliantly release the food into the user's mouth. Overall, Kiri-Spoon combines the familiar and comfortable shape of a standard spoon with the increased capabilities of soft robotic grippers. In what follows, we first apply a stakeholder-driven design process to ensure that Kiri-Spoon meets the needs of caregivers and users with physical disabilities. We next characterize the dynamics of Kiri-Spoon, and derive a mechanics model to relate actuation force to the spoon's shape. The paper concludes with three separate experiments that evaluate (a) the mechanical advantage provided by Kiri-Spoon, (b) the ways users with disabilities perceive our system, and (c) how the mechanical intelligence of Kiri-Spoon complements state-of-the-art algorithms. Our results suggest that Kiri-Spoon advances robot-assisted feeding across diverse foods, multiple robotic platforms, and different manipulation algorithms.

Figures (15)

• Figure 1: Kiri-Spoon is a spoon-shaped kirigami utensil specifically designed for robot-assisted feeding. (Left) Robot arms equipped with Kiri-Spoon can robustly acquire foods from the plate, safely carry those morsels to the human, and then seamlessly transfer items into the user's mouth. (Right) It is challenging for robot arms to dexterously manipulate traditional utensils such as forks and spoons. By comparison, Kiri-Spoon makes the robot's task fundamentally easier by flexibly wrapping around the desired foods. This capability enables Kiri-Spoon to function as a fork (pinching foods) or as a spoon (scooping foods).
• Figure 2: Actuating and releasing Kiri-Spoon. The core element of Kiri-Spoon is an elliptical kirigami sheet with discrete ribbons orthogonal to the applied forces. Retracting one end of Kiri-Spoon causes this $2$D sheet to buckle and form a $3$D bowl with increasing curvature, thereby encapsulating food items.
• Figure 3: Design of Kiri-Spoon. (Left) A kirigami sheet is used to grasp, hold, and release food items. This sheet is composed of multiple ribbons: a boundary ribbon that surrounds the sheet, discrete ribbons that form the base of the spoon, and mesh ribbons that interconnect the discrete ribbons. (Right) The kirigami sheet is supported on one end by a flexible hoop. The other end is extended or retracted by a 1-DoF linear actuator. During eating, users interact with the flexible hoop and kirigami sheet.
• Figure 4: Two variations of Kiri-Spoon's mesh. (Top) For most foods a discrete mesh is sufficient. (Bottom) However, for liquid foods such as soups, a thin membrane can be mounted to the kirigami sheet. The resulting continuous mesh prevents liquids from falling out of the bottom of Kiri-Spoon.
• Figure 5: Demonstration of the flexible hoop. This flexibility is not only comfortable for users, but it also enables Kiri-Spoon to bend along the surface of plates and bowls. We leverage this flexibility to deploy Kiri-Spoon like a fork and pinch foods that are directly beneath the kirigami structure.