Printing porous and flexible 3D objects

First published in  Dec.22, 2013

German Engineer Kai Parthy introduced his Filament Laywoo-D3 more than a year ago. “This is a year in my life which I will not soon forget.” says Kai. “It was not easy to respond to all the inquiries from all over the world and meanwhile to raise production from small to large quantities due to demand.” In the past year Kai has also developed material Bendlay and Laybrick that contains fillers. But he didn’t stop there.

Kai’s new plan is to complete a range of four pre-structured 3D printing materials:

  • FDM Filaments (new PORO-LAY line, a two-in-one filament)
  • Light curing resins
  • Sinterpowders
  • Other materials based on similar technique and Polymers

Prototypes of the first resulting material-line, which Kai is introducing today, are called PORO-LAY Filaments. In contrast to previous filled materials, 3D-objects built from PORO-LAY are filled with emptiness – namely pores. The PORO-LAY is printable with all standard home 3D printers.

But what’s the trick? How can you get foam or more fibers in 3D printed objects? According to Kai, the process works as follows:

  • First you print your object with PORO-LAY, a stiff filament. You don’t need anything extra, no second hotend, simply print your object as you always do.
  • Next you rinse out the water soluble polymer component which is hidden and homogeneously dispersed inside the filament by shaking your 3D printed object in water.
  • After drying your object will be porous. The technical term for this process is ‘extraction with solvent ‘.

This big X is a standard object for tests. Before rinsing.

Left: The 3D printed X is stiff before rinsing. Right: After rinsing in water the 3D printed X has properties like a soft-rubber (very flexible) with mirco-pores.

Kai further describes the procedure of rinsing as follows:

  • Place the 3D printed object in water and add a drop of soap in. Then keep the object in water for 1 to max. 4 days (depends on which filament of the PORO-LAY line (1, 2, 3, 4) you are using). Water is the best choice for a solvent to handle this process.
  • Shake the object in water, or stir the water / change the water from time to time because it gets milky from the soluble component after a while.
  • Handle the purging procedure accurately until no soluble component remains in the porous structure of the object.
  • Dry the object.

The photos below taken from electron microscope show structure inside the filament BEFORE printing and AFTER printing and rinsing.

Lay-Tekkks: This material has a paperlike thin fibrous surface.

Lay-Tekkks: single magnification of fibers

Lay-Tekkks: electron beam magnification: 24x


Lay-Tekkks: electron beam magnification: 200x
firmly packed longitudinal oriented fibres, some stick out

latent porous structures, already 3d-printed, but not yet rinsed, 100x

electron beam magnification: 50x
Filament rinsed in water, with clearly visible porous structures

Clearly visible porous structures, 200x

You can also check out the video below for details.

But what ingredients are homogeneously dispersed in the PORO-LAY? Kai told us that he generally uses a blend of two main components, A+B for his new filament. A is a functional component, for example an Elastomer (i.e. a rubber-like), B is a soluble component (e.g. PVA, sugar, salt, or soluble resins). “In nature you may also find similar mixtures of two or more (mineral) components in stones, e.g. in granite or marble. ” says Kai.

Then A and B are mixed (blended) together, pelletized and extruded to a filament of 3.0 mm or 1.7 mm. “I can choose from a dozen of different Polymers for the mixture of A and B.” says Kai. The resulting materials have different possible characteristics for a lot of applications which we will describe further below.

The Poro-lay line includes four different materials:

  1. Lay-Felt
  2. Lay-Tekkks
  3. Lay-Fomm
  4. Gel-Lay

In general all filaments have structure inside, some are more like a foam, with holes, others are more like a felt, with elongated, fibrous holes. The main characteristics of different PORO-LAY filaments are:

1. Lay-Felt: Lay-Felt contains stiff or soft felt-fibers, it may be used in the following applications: 3D membranes, filters, semipermeable, future cloths, and artificial paper.

2. Lay-Tekkks: Lay-Tekkks and Lay-Felt are both fibrous like felt, but Lay-Tekkks has thinner, finer fibrous structures. Lay-Tekks can be used for making oriented fibers, stacked fibers, future cloths, and tissue.

3. Lay-Fomm: Lay-Fomm is full with holes, it feels like very soft rubber. It may be used in making micro-foam, sponges, bio-cells, elastics, and bendable suits.

4. Gel-Lay: This material is highly porous and the printed objects are very unstable. Its applications could be: objects in water, marine organism flow simulation, and bio-mechanics.

Patents are pending for pre-structured 3D printing materials. Kai also welcomes partners. He plans to start selling the PORO-LAY line in first or second quarter of 2014.


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