As stated in previous posts, we envisage this core to be made out of whatever material is suited to the end use. It is therefore apparent that there can be different ways of manufacture depending on that use. For example, a metal sheet would be cut out into the required pattern, and then after creasing and scoring, would be folded into the required core configuration. Similarly, paper or cardboard would be diecut and folded. Another method would be to chop-spray a material over a prepared form. Another method which occurred to us more recently, is that of vacuum forming, and as the photos indicate, we set about making a rig that would enable us to prove the concept. The picture at left shows a single formed panel, approximately 12" in diameter and 1" core depth. and pictures 2 and 3 show how the panels edge-lap together to form required shapes.
- ePTFE. (expanded polytetrafluoroethylene ) The use of modified ePTFE surface in hernia repair enables early tissue attachment, reduces adhesions, and could reduce the incidence of recurrences. This would be the first layer that is printed (smooth side down)
- Polypropylene. This material has been used for the past 20 years because of its stability, strength, inertness and handling qualities. Polypropylene is overprinted on the PTFE layer and provides the basic structure of the lattice.
- Collagen. A final layer of collagen is printed to encourage speedy host tissue incorporation into the latticework.
- May result in the permanent repair of the abdominal wall, to reinforce and replace tissue for long-term stabilization of the abdominal wall.
- Ingrowth characteristics that mimic normal tissue healing. May stimulate adequate fibroblastic activity for optimum incorporation into the tissues. May prevent adhesions. The ePTFE protects the edge of the lattice minimizing tissue attachment to the material.
- Strong. May provide sufficient biomechanical strength to meet physiological requirements in order to permanently protect the fascial defect.
- Pliable. It has elasticity in more than one dimension, allowing it to stretch in more than one direction and then return to its original shape. Easily assumes the conformity of the abdominal wall musculature anatomy
- Handling characteristics should be amenable to laparoscopic instruments.
- The lattice may have an adequate adhesive quality that requires minimal or no additional fixation, even for large defects.
- Cuts easily without fraying.
By using 2 sets of dies (A) - top and bottom, shown here in red and pink, and placing them between top and bottom clamp plates (B), when the clamps are drawn together, the dies, which are constrained by a sheet of polyester which we have called "living hinge," (C) come together to crease and fold the metal sheet. D, E and F show the range of motion where D is the start before any compression, E is half complete and F is a closed version of conceptual Hexaflex honeycomb.
If this proposal works, it will be the first time that Hexaflex honeycomb has been manufactured in any sort of quantity. The project will call for about 50- 75 sheets using a hexagon size of 12" and a core depth of around the same. We will keep you posted on the project as we move forward.
Compression forces can be tailored to optimize the structure by strategically infusing syntactic foam of varying crush strengths. The high crush strength and low density of syntactic foam makes it an ideal core material for hybrid sandwich composites.
This latest modification to the property mix of Hexaflex, indicates a strong likelihood that delamination can be avoided in most incidences, a condition that the aerospace industry will no doubt welcome.
We have known for some time that one of the best ways to manufacture Hexaflex, using a variety of different materials, is to use 3D printing. After some months of file preparation and modification, we submitted our designs to Shapeways, obtaining some 150 3D printed tiles, a mixture of hexagons and squares, and assembled them into a sheet of Hexaflex.
One of the first things we noticed was the comparative ease by which they could be assembled into such objects as spheres, domes, buckeyballs, nanotubes, torus/donuts, terraced planes, rhombic dodecahedrons and parabolic dish structures, to name but a few.
This unorthodox building kit could be an educational toy incorporating multiple layers of learning. These layers, which promote both critical thinking and discovery, include:
1. Exploring the world of polyhedra.
2. Discovering the intricacies of Nanotechnology.
3. Creating robotic structures.
4. Integral construction possibilities with Lego
Incorporating a earlier invention called the Nodlet truss into the hexaflex pattern, we were surprised to discover an entirely new form of curvable lattice, not unlike a mechanical skin...
Using components engineered in 3D printed nylon, inventor Bob Burdon discusses a newly-discovered foldable lattice created using Hexaflex and a earlier invention called the Nodlet. We are currently embarking on a program of reaching out to major aerospace and automotive companies who are looking for adaptive structures that change shape according to desired performance criteria.
The future is exciting. With 3D printing fast becoming a legitimate manufacturing platform, and machines being developed that can print multiple materials concurrently - a concept completely in sync with the Hexaflex system, it remains to be seen where Hexaflex will fit in, and which applications will be among the first to find a viable and sustainable market.