arXiv subjects

Daniel Widerker

Publications and source records attributed to Daniel Widerker.

4 recordsLinked to original sources

arXiv2026

Modeling the Thermal Behavior of Photopolymers for In-Space Fabrication

Future long-duration space missions will require in-situ, on-demand manufacturing of tools and components. Photopolymer-based processes are attractive for this purpose due to their low energy requirements, volume efficiency, and precise control of curing. However, photopolymerization generates significant heat, which is difficult to regulate in microgravity where natural convection is absent, leading to defects such as surface blistering and deformation. In this work, we combine experimental studies and modeling to address these thermal challenges. We report results from International Space Station (ISS) experiments and a dedicated parabolic flight campaign, which confirm that suppressed convective heat transfer in microgravity exacerbates thermal buildup and defect formation. Building on these observations, we present a predictive thermal model that couples heat transfer, light absorption, and evolving material properties to simulate polymerization and temperature evolution under terrestrial and microgravity conditions. Laboratory validation demonstrates strong agreement between model predictions and measured temperature profiles. Applying the model to the ISS experiments, we show that the model accurately reproduces experimentally observed blistering in TJ-3704A, a commercial acrylate-based polymer resin, while also predicting defect-free outcomes for Norland optical adhesives. The model functions as a design tool for defect-free in-space manufacturing, enabling selection of polymer properties, exposure strategies, and environmental conditions that together inhibit excess thermal buildup, paving the way for scalable, reliable in-situ manufacturing during future missions.

cond-mat.mtrl-sci↗

arXiv2025

In-space manufacturing of optical lenses: Fluidic Shaping aboard the International Space Station

In-space manufacturing technologies are vital for enabling advanced space missions and addressing logistical limitations of space exploration. While additive manufacturing has progressed rapidly, it still falls short of delivering the ultra-smooth surfaces required for optical elements. Fluidic Shaping is a novel method that harnesses surface tension under microgravity to form optical components with exceptionally smooth surfaces. This study demonstrates the feasibility and potential of Fluidic Shaping as a method for manufacturing optical components in space through two experiments performed aboard the International Space Station (ISS) during the Ax-1 mission. The first experiment involved fabricating centimeter-scale polymer lenses, solidifying them via ultraviolet (UV) curing, and analyzing the resultant optics upon their return to Earth. While sub-nanometric surface smoothness was achieved, some polymer lenses displayed unexpected thermo-chemical deformations, indicating complex polymerization dynamics unique to the microgravity environment. In the second experiment, a large-scale, 172 mm diameter water lens was deployed, confirming Fluidic Shaping's scalability and demonstrating basic optical functionality through image analysis. These experiments collectively underline the technique's relevance for both small-scale optics and large-aperture applications. Our results highlight critical considerations for future research, including optimizing polymerization processes and refining liquid-handling methods to advance practical, in-space optical manufacturing capabilities.

physics.optics↗

arXiv2024

Fluidic Approach to Corrective Eyewear Manufacturing in Low-Resource Settings

Limited access to corrective eyewear remains a significant medical, societal, and economic challenge, even in the 21st century. More than 1 billion people suffer from uncorrected vision impairment, with the vast majority residing in developing countries. Decades of philanthropic efforts failed to supply even a small fraction of the demand, whereas local manufacturing using standard machining technologies remains out of reach due to inadequate resources. We here show that the Fluidic Shaping approach can be utilized to create a new manufacturing modality for high-quality ophthalmic lenses that entirely eliminates the need for machining, and instead uses surface tension to shape liquid polymer volumes into prescription lenses. We present a compact device wherein a liquid photopolymer is injected into an elliptical frame submerged within an immersion liquid of equal density, resulting in two liquid surfaces whose minimum-energy states correspond to two lens surfaces. After several minutes of curing, a complete solid lens is obtained, requiring no post-processing. We provide an analytical model and experimental validation, showing that all spherical and cylindrical corrections can be attained by simply controlling the volume of the polymer and the frame's eccentricity. We demonstrate the fabrication of complete eyeglasses that meet and exceed industry standards, relying solely on a 1 gallon water container integrated with an array of low-power LEDs.

physics.app-ph↗

arXiv2022

Fluidic Shaping and in-situ Measurement of Liquid Lenses in Microgravity

In the absence of gravity, surface tension dominates over the behavior of liquids. While this often poses a challenge in adapting Earth-based technologies to space, it can also provide an opportunity for novel technologies that utilize its advantages. In particular, surface tension drives a liquid body to a constant-mean-curvature shape with extremely smooth surfaces, properties which are highly beneficial for optical components. We here present the design, implementation and analysis of parabolic flight experiments demonstrating the creation and in-situ measurement of optical lenses made entirely by shaping liquids in microgravity. We provide details of the two experimental systems designed to inject the precise amount of liquid within the short microgravity timeframe provided in a parabolic flight, while also measuring the resulting lens characteristics in real-time using both resolution target-imaging and a Shack-Hartmann wavefront sensing. We successfully created more than 20 liquid lenses during the flights. We also present video recordings of the process, from the lenses creation during microgravity and up until their collapse upon return to gravity. To the best of our knowledge, this is the first time that a purely liquid lens has been created in microgravity, which demonstrates the feasibility of creating and utilizing liquid-based optics in space.

physics.optics↗