Epidermal Wearable - Customized Arm Cast

Research @ MIT Media Lab | 2018

#customization #3D #density #stiffness #curvatures

After conducting research on photogrammetry, I became interested in the relationship between digital fabrication, computational data, and visual elements of 3D modeling—including, points, lines, polygons, and shades.

Idea

 

In connection with the 3D modeling of an arm in the Capture of figures project, I seek a rational way to use various dimensions of 3D modeling that consist of points, lines, curves, polygons, and depths and how these visual elements could be extracted and modified to interact with physiology. In this project, I focused on digital modification: the interchanging of 2D and 3D and the density of patterns and shapes on materials.

Agenda

 

Week 4-5: Remodeling on Rhinoceros

The 3D data I got from 3DF Zephyr was a mesh-based model, which contained millions of points that were too large for the Rhino to proceed. After converting a mesh to NURB, the mesh was reduced. Then, the outlines of the 3D model were taken out horizontally and vertically in order to eliminate unnecessary curves and points with a command called Contour. Then, the extracted lines, "bones" of the structure, were wired up based on the curves to rebuild the model.

*Hover over to see more details

Week 5-6: Computer Aid Design and 2-Dimensional Patterns

As the goal of this project is to understand the link between the density of patterns to the physical materials, the patterns need to flow along surfaces of the 3D model. In order to do so, I first used Adobe Illustrator to design the 2-dimensional patterns. After exporting the 2D design from Illustrator to Rhino, I extruded it into a 3D object. Then, I “flow-along-surf it on top of the surface of the 3D arm that was achieved previously. 

Week 7-8: Testing and Analysis of the Density and Thickness

Before delving into my analysis of the density and thickness of patterns, I tested the command, flowalongsrf, with the more abstract design I created using Adobe Illustrator. After a bit of trial and error, I pursued a way to successfully project a certain design on the targeted area of the 3D model.

Prototyping sample

Then, I designed a sample that contained various line weights with different thickness and 3D printed it. A closer look at the structure gave some new insights into the factors that significantly impact change in form. The length, thickness, and proximity between each pattern and the shapes all affect the movement of material. These contribute to change in shape. Each line weight’s direction of the fold, flexibility, and stiffness all varied when the sample was bent.

Comparing the Density of the Pattern

After preliminary observation of different line weights and how they affect change in shape, I designed honeycomb patterns with two different densities: one with closer proximity with density in a smaller shape and one with the larger scale of pattern and proximity. 

High density of patterns 

It is more flexible and less resistant to force in changing shapes. Therefore, it is suitable for the protruded and stiff areas of the skin.

Low density of patterns 

The large scale of the pattern in samples allows it to go back to its original shape. Therefore, it is suitable for smoother curves that cover the large portion of the surface.

Testing on the ball

With the aim of seeing how it works with the curves of the object, I attempted to wrap it around the ball.

The high density of pattern

It distributes the force evenly, flowing on the curves.  With its flexible properties, it can be concentrated around the area where it needs high tensility of the material and needs more compression.

Low density of patterns 

The applied force concentrates in one area and folds in the regular direction. The structure will bend along the linear shape of the pattern, therefore controlling the angle of the bend.

Week 9-10: 3D Modeling the Customized Arm Cast

With the new insight on the correlation of density of shapes on the object, I applied this concept to the stiffness data of skin achieved by SkinBot. After implementing the command, flowalongsrf, which I learned during the week 5-6, the pattern that corresponded with the skin textures, the customized wearable was 3D printed. The further data and work will be presented in the near future after the approval process.

Manufacturing Process

Because of the limitation of the 3D printer, Foarmlab, the customized 3D model was divided into two parts. The two parts were later connected by multiple curing processes under UV light.​

Future Implication

This exciting digital fabrication opens up the limitless possibility of the additive manufacturing system, as well as customization in wearables. In particular, it can be used for medical purposes where an arm cast would not be breathable. However, with the help of shape, density, and thickness, patterns can be molded around the body part with negative spaces that will allow the skin to breathe and be flexible while the bone structure stays in place.

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Alice Hong