# Embedded Printing of Integrated Quantum Dot Waveguide Deformation Sensors

## TL;DR

Researchers developed a flexible sensor using quantum dots and silicone waveguides to detect structural deformation with high precision.

## Contribution

The novel embedded printing process integrates quantum dots into waveguides for self-referenced deformation sensing in a single manufacturing step.

## Key findings

- Angular deflections up to 9.5° were detected with sub-1° resolution using ratiometric evaluation.
- Printed waveguides showed optical attenuation losses of 0.81±0.02 dB/cm at 625 nm.
- The sensor enables spatially resolved integration of quantum dot-functionalized silicone in a viscoplastic support medium.

## Abstract

We present an optical deformation sensor additively manufactured via an embedded printing process that enables the direct integration of colloidal quantum dots into multimode silicone (PDMS) waveguides. The sensor consists of two parallel waveguide strands, one of which is locally functionalized with CdSe/CdS quantum dots serving as fluorescent emitters. When narrow-band UV light at 405 nm is coupled into the non-functionalized strand, structural deformation alters the conditions of total internal reflection, thereby changing the optical interaction between both strands. This leads to a deformation-dependent variation in the fluorescence shift-affected intensity ratio, which serves as a self-referenced signal for angle determination. Using ratiometric evaluation, angular deflections of up to 9.5° are detected with a resolution below 1° (2σ confidence), representing the performance of an initial functional prototype. The embedded printing process allows the voxel-wise adjustment of the material composition within a viscoplastic support medium and thus the spatially resolved integration of quantum dot-functionalized silicone. Attenuation losses of 0.81±0.02dB/cm at 625 nm confirm the optical suitability of the printed waveguides. This approach combines optical sensing and structural flexibility within a single manufacturing step and establishes a pathway toward fully integratable deformation-sensing elements for soft robotic and wearable systems.