Summary

[001] Provided herein is a biodegradable alternative to polyurethane-based foam cushioning, inspired by biomimicry, for use in the hospitality industry.

Brief Description of the Drawings

[002] Figure 1 illustrates one embodiment of triple-helical spring as described herein.

[003] Figure 2 illustrates a second embodiment of a triple-helical spring as described herein.

[004] Figure 3 is a top view of a set of spring units joined together to form a skeletal subunit.

[005] Figure 4 shows two examples of skeletal subunits.

[006] Figure 5 shows schematic diagrams of triple-helical springs described herein.

[007] Figure 6 shows the compressibility of different triple-helical springs.

[008] Figure 7 is a schematic diagram of different triple-helical springs (72A, 73A1, 73A2, and 73B1).

[009] Figure 8 shows the compressibility of triple-helical springs (72A, 73A1, 73A2, and 73B1).

[010] Figure 9 is a schematic diagram showing hexagonal lattice grids 73-A3 and 73-B2.

[011] Figure 10 shows the compressibility of two spring grids: 73-A3 and 73-B2.

[012] Figure 11 shows the compressibility of Hl-based arrays.

[013] Figure 12 shows the effect on compressibility of compressed nanofiber ("CNF") fill.

[014] Figure 13 shows the effect on compressibility of CNF:Pulp fill mixtures.

[015] Figure 14 shows the effect on compressibility of different CNF:Pulp fill mixtures.

[016] Figure 15 shows the effect on compressibility of different CNF:pulp:chitosan fill mixtures.

[017] Figure 16 shows the effect of compression cycle and fill material on compressibility and recoil of an unfilled J3 structure.

[018] Figure 17 compares the compressibility and recoil of an unfilled J3 structure to J3 structures filled with different materials.

[019] Figure 18 compares the compressibility of filled and unfilled J4 structures. [020] Figu re 19 compares the compressibility of unfilled to filled J4 structures.

[021]

Definitions

[022] The Pitch of a helical spring is the height of 1 complete loop of the helix.

[023] The Pitch Angle of a helical spring is the arc (in degrees) between the vertical axis and the plane of the helix. The mathematical definition of the helix angle is:

Angle (°) = (180/p)-arctan(2pR/Pitch) where the 180/p converts from radians to degrees.

[024] The Radius of a helical spring is the distance between the center vertical axis and perimeter of the circle formed by 1 complete loop of the helix.

[025] Support Factor (also known as "compression modulus") = Force required to compress a sample 65% / Force required to compress a sample to 25%. A higher Support Factor equals a firmer cushion. The force is typically expressed as "indentation force" or "IFD" and is measured by compressing a 50" square plate into the cushion.

Detailed Description

[026] Provided herein is a cushion comprising a skeleton comprising a plurality of

biodegradable springs; means for connecting at least two of the springs; and a biodegradable tissue; wherein the tissue is disposed in the skeleton . In one alternative embodiment, the springs and the connecting means are comprised of the same material.

[027] A cushion as described herein will typically have a support factor in the range from about 1.8 to about 2.6.

[028] The springs may be printed by a 3-D matrix printer. The springs may be comprised any suitable material. When the springs are printed by a 3-D matrix printer, the springs may be comprised of any suitable material which is compatible with 3-D matrix printing. Examples of such materials include polylactic acid (PLA), acrylonitrile butadiene styrene, polylactic acid- polyhyd roxyalkanoate (PLA-PHA), and mixtures thereof. In an exemplary formulation, PLA-PHA has a density of about 0.00123 g/mm ³ .

[029] The springs are advantageously helical in structu re. Each spring may comprise a single helix, as shown in Fig. 1 and 2, or may comprise multiple helices which are joined together, as shown in Fig. 3 and 4. Typically, a spring will comprise no more than six helices; advantageously, the springs may comprise single, double, or triple helices. A schematic diagram showing an exemplary single helix spring is shown in fig. 1. When this spring has a volume of 2,204.14 mm ³ , it will comprise about 2.71 g of PLA-PHA.

[030] In one embodiment, when compressed by about 65%, the springs recoil about 100%.

[031] The springs may be connected by bringing the springs into contact with one another, and then heating the contacting sections of the springs until they melt and fuse. Alternatively, the contacting sections may be treated with a chemical agent which causes the contacting sections to fuse. In an alternative embodiment, the springs are connected with biodegradable linkers, which may comprise the same material as the springs, or may be comprised of a different biodegradable material.

[032] As noted above, the cushion described herein further comprises a biodegradable tissue disposed within the skeleton. In one embodiment, the biodegradable tissue comprises a low- density, high-void volume material. Suitable low-density, high-void volume materials may comprise one or more of a natural polymer, a synthetic polymer, and a crosslinkable resin. The low-density, high volume material may also comprise a cellulosic material. In one embodiment, the cellulosic material is a microfibular cellulose (also known as "cellulose nanofibers"). The cellulosic material may optionally be lyophilized.

[033] The tissue may further comprise up to about 15 wt% of chitosan or xylitol. The tissue may further comprise up to about 50 wt% of a filler. The filler may optionally be selected from the group consisting of paper pulp and sawdust.

[034] The cushions described herein may further comprise "ligaments," which are means for attaching the tissue to the skeleton. Where the skeleton is produced by 3D printing, the ligaments can be incorporated into the 3D printing media of the "skeleton" as a second auxiliary small molecule or polymer with reactive groups. The reactive groups bond to the tissue through contact, or by exposure to heat, light, or some other form of energy, or by exposure to a chemical agent.

[035] In one embodiment, the skeleton contains anhydride or carboxylic acid linkages which could react with the alcohol groups of cellulose in the tissue. Alternatively, the tissue may comprise reactive groups, wherein a secondary additive or chemically functionalized primary tissue component can react with appropriate groups in the primary or auxiliary components of the skeleton.

SPECIFIC EXAMPLES

Example 1 - characteristics of different triple-helical springs

[036] The major focus has been to create a design that allows compression through a range of Z-dimensions to allow for ~100% recoil after a 65% relative compression. In addition to accomplishing this difficult task, the ancillary goal has been to minimize the amount of polymer required for these structures to reduce cost and weight of the final finished cushion .

[037] We tested triple-helical springs which were produced from PLA-PHA on a 3d matrix printer. The springs had a helix angle of 65-80°, a number of loops from 1-2, and a helix radius of 11.5 or 14.5 mm.

Schematic diagrams of these springs are shown in Fig. 5A & B.

[038] The amou nt of force (N) required to compress each spring type by 65% is shown in Fig. 6. The best designs for recovery and lack of plastic deformation were 72A (98% recovery) and 72-H1 (91% recovery). Spring 72-H4 exhibited 95% recovery, but with plastic deformation.

Example 2 - Compressibility of different triple-helical springs

[039] We tested the amount of force required to produce 25% compression in four different triple-helical springs. Figure 7 shows the four springs tested: 72A, 73A1, 73A2, and 73B1 (from left to right). Figure 8 shows the amount of force (N) required to produce a particular amount of displacement in each spring type.

Example 3 - Compressibility of hexagonal lattice grids

[040] We tested the amount of force required to produce 25% compression in two different hexagonal lattice grids of seven triple-helical springs. Figu re 9 shows the two spring grids tested : 73-A3, and 73B2 (from left to right). Figu re 10 shows the amount of force (N) required to produce a particular amount of displacement in each spring grid type. Example 4 - Compressibility of Hl-based arrays

[041] We tested the amount of force required to produce 65% compression in different H l- based spring arrays: 72-I1-Z15-2 (7 X 72A springs, 33 spacing); 72-J2-Z15-2 (7 Spring grid of 72H1 with 4mm ribbon); 72-J3-Z15-4 (3 spring grid of 72H 1 with 3 mm ribbon and no supports); 72-J3-Z16-6 (3 spring grid of 72H1 with 3 mm ribbon and supports); and 72-J4-Z15-2 (3 spring grid of 72A with 3 mm ribbon). Results are shown in Fig. 11.

Example 5 - Effect on recoil of CNF fill

[042] We tested the effect of cellu lose fill (compressed nanofibers, "CNF") on the recoil of a 3X3 spring grid (17 mm spring height, 75mm width). The resu lts are shown below.

Scaffold Fill Type % Compression Start Final Recovered % of Length

Example 6 - Effect on compressibility of CNF fill

[043] We tested the effect of cellu lose fill (compressed nanofibers, "CNF") on the force (N) required to produce 25 % compression in hexagonal lattice grids of seven springs. The resu lts are shown in Fig. 12.

Example 9 - Effect on compressibility of CNF:Pulp fill mixtures

[044] We compared the effect of compression of hexads on different mixtu res of CN F and paper pulp. We tested three different fills: CNF alone (1:0 CNF:pulp); a 75:25 mix of CNF:pulp; and a 1:1 mix of CNF:pulp. Resu lts are shown in Fig. 13.

Example 10 - Preparation of CNF/Pulp blends

[045] We prepared five different CNF/Pulp blends as shown below.

Reagent Stock% 258-15A 258-25B 258-15C 258-15D 258-15E

CNF delivery form 2.99 130 97.5 65 32.5 0

Sappi pulp 4.6 0 21.125 42.25 63.375 130 Water 100 0 0 0 0 0

% Sappi pulp 0 25 50 75 100

% total solids 2.99 3.28 3.62 4.05 4.6

Example 11 - Effect on compressibility of different CNF:pulp fills

[046] We tested the effect of different mixtures of CNF:pu lp on the amount of force req uired to produce a particular displacement. Results are shown in Fig. 14.

Example 12 - Effect on compressibility of different CNF:pulp:chitosan fills

[047] We compared the effect of 100% CNF fill on compressibility of a J3 structure to 85:15 CNF hitosan fill and 42.5:24.5:15 CNF:pu lp:chitosan fill. The results are shown in Fig. 15.

Example 13 - Effect on compression cycle and fill material on compressibility and recoil of J3 structure

[048] We compared the compressibility and recoil of an unfilled J3 structure on the first and second compression cycle. The results are shown in Fig. 16 and the table below.

Sample ID Height Initial (mm) Height After (mm) % Recoil from Initial

J3-cycle 1 45.48 41.32 91%

J3-cycle 2 41.32 37.57 91%

[049] Next, we compared the compressibility and recoil of a filled and an unfilled J3 structure. The results are shown in Fig. 17 and the table below.

Sample ID Height Initial (mm) Height After (mm) % Recoil from Initial

J3 45.48 41.32 91%

J3, 100% CNF 45.84 37.48 82%

[050] Next, we compared the compressibility and recoil of unfilled J3 structure to J3 structu res filled with different materials. The results are shown in the table below. Sample ID Height Initial (mm) Height After (mm) % Recoil from Initial

Example 14 - Effect on compression cycle and fill material on compressibility and recoil of J3 structure

[051] We compared the compressibility of filled and unfilled J4 structures. Different fills employed include 95:5 CNF:Chitosan; 90:10 CNF:Chitosan; 85:15 CNF:Chitosan; 47.5:47.5:5 CNF:Pulp:Chitosan; 45:45:10 CNF:Pulp:Chitosan; The results are shown in Fig. 18.

[052] Next, we compared the compressibility and recoil of an unfilled J4 structure to J4 structures filled with different materials. Different fills employed include 100% CNF; 85:15 CNF:Chitosan; and 42.5:42.5:15 CNF:Pulp:Chitosan. The results are shown in Fig. 19 and the table below.

Sample ID Height Initial (mm) Height After (mm) % Recoil from Initial

J4 36.31 34.19 95%

J4, 100% CNF 36.12 31.28 87%

J4, 85:15 38.92 30.34 78%

CNF:Chitosan

J4, 42.5:42.5:15 39.22 25.11 64%

CNF:Pulp:Chitosan

[053] We repeated the experiment using a wider variety of mixed fills, The results are shown in the table below.

Sample ID Height Initial (mm) Height After (mm) % Recoil from Initial

J4 36.31 34.19 95% J4, 95:5 CNF:Chitosan 37.28 24.43 65%

J$, 90:10 36.19 24.11 67%

CNF:Chitosan

J4, 85:15 37.36 27.17 73%

CNF:Chitosan

J4, 47.5:47.5:5 37.25 27.64 74%

CNF:Pu lp:Chitosan

J4, 45:45:10 37.49 26.59 71%

CNF:Pu lp:Chitosan

J4, 42.5:42.5:15 37.83 28.87 76%

CNF:Pu lp:Chitosan

Example 16 - CMC-based CNF Thermal Foam

[054] We developed two different formulas for CMC-based CNF thermal foam fills, and used those fills to fill B2 hex/J3 Triad cages. The formulas for the fills are shown in the table below.