3D-printed Soft Optical sensor with a Lens (SOLen) for light guidance in mechanosensing

2026-02-19

AI Summary

This work addresses the performance degradation of optical sensors in monolithic soft robots caused by stray light, leakage, and ambient interference. To overcome this, the authors propose a Y-branch waveguide-based differential sensing scheme integrated with a 3D-printed lens. Mechanical deformation induces lens rotation and focal spot displacement, modulating the optical power distribution between the two waveguide branches to enable highly sensitive differential detection of both direction and magnitude of motion. Leveraging a modified acrylate-based polyurethane resin—formulated with lauryl acrylate—and DLP 3D printing, the study achieves, for the first time, a monolithic soft optical sensor with an embedded, interface-free lens. A transferable workflow spanning material formulation, optical modeling, and simulation-driven design is established. Experiments demonstrate repeatable, branch-selective responses across multiple cycles with sub-millimeter lens features, significantly enhancing sensing performance.

Technology Category

• Intelligent Robots: Multimodal Perception & Sensor Fusion
• Humans and AI: Brain-Sensing and Analysis
• Computer Vision: 3D Computer Vision

Application Category

• Responsible Web: Human-perceived consequences of algorithmic deployment on the web
• Systems and Infrastructure for Web, Mobile and WoT: Experiences and lessons learnt from Web-based algorithms and system deployments
• Security and Privacy: Data transparency and provenance

Abstract

Additive manufacturing is enabling soft robots with increasingly complex geometries, creating a demand for sensing solutions that remain compatible with single-material, one-step fabrication. Optical soft sensors are attractive for monolithic printing, but their performance is often degraded by uncontrolled light propagation (ambient coupling, leakage, scattering), while common miti- gation strategies typically require multimaterial interfaces. Here, we present an approach for 3D printed soft optical sensing (SOLen), in which a printed lens is placed in front of an emitter within a Y-shaped waveguide. The sensing mechanism relies on deformation-induced lens rotation and focal-spot translation, redistributing optical power between the two branches to generate a differential output that encodes both motion direction and amplitude. An acrylate polyurethane resin was modified with lauryl acrylate to improve compliance and optical transmittance, and single-layer optical characterization was used to derive wavelength-dependent refractive index and transmittance while minimizing DLP layer-related artifacts. The measured refractive index was used in simulations to design a lens profile for a target focal distance, which was then printed with sub-millimeter fidelity. Rotational tests demonstrated reproducible branch-selective signal switching over multiple cycles. These results establish a transferable material-to-optics workflow for soft optical sensors with lens with new functionalities for next-generation soft robots

Problem

• soft optical sensor
• 3D printing
• light propagation
• monolithic fabrication
• mechanosensing

Innovation

• 3D printing
• soft optical sensor
• integrated lens
• monolithic fabrication
• mechanosensing