COLD DRAW PROGRAMMABLE GRAYSCALE DIGITAL LIGHT PROCESSING 3D PRINTED SHAPE-MORPHING STRUCTURES AND METHODS OF FORMING THE SAME

Abstract

A shape-morphing structure includes a cold draw programmable grayscale digital light processing 3D printed unitary hinge component comprising at least one glassy state portion and at least one rubbery state portion. The at least one glassy state portion has a glassy state recovery temperature and the at least one rubbery state portion has a rubbery state recovery temperature and different than the glassy state recovery temperature.

Description

TECHNICAL FIELD

The present disclosure generally relates to shape-morphing structures, and particularly to 3D printed shape-morphing structures.

BACKGROUND

Shape-morphing structures, i.e., structures that change shape in response to external stimuli, are used or employed in systems or devices such as soft robotic systems, deployable systems, wearable devices, and shape-shifting antennas, among others. However, the design, development and/or manufacturing of such shape-morphing structures can be time and/or cost intensive.

The present disclosure addresses issues with the design, development and/or manufacturing of shape-morphing structures, and other issues related to shape-morphing structures.

SUMMARY

In one form of the present disclosure, a shape-morphing structure includes a cold draw programmable grayscale digital light processing (g-DLP) 3D printed unitary hinge component comprising at least one glassy state portion and at least one rubbery state portion.

In another form of the present disclosure, a shape-morphing structure includes a cold draw programmable grayscale digital light processing (g-DLP) 3D printed unitary hinge component formed from a resin and comprising at least one glassy state portion and at least one rubbery state portion. In addition, the resin includes a donor moiety, ab acceptor moiety, and a rigid moiety. The donor moiety is in the form of an acrylate monomer with a side group comprising at least one of a free carbonyl, a primary amine on an acrylate, a secondary amine on an acrylate, and a tertiary amine on an acrylate. The acceptor moiety is different than the donor moiety and in the form of an acrylate monomer with a side group comprising at least one of a free hydroxy, a primary amine, secondary amine, and an imine. And the rigid moiety is in the form of an acrylate monomer with a side group comprising of one or more of a cyclohexyl, a substituted cyclohexyl, and a bicyclic structure.

In still another form of the present disclosure,

These and other features of the g-DLP 3D printed physical information storage units and their manufacture will become apparent from the following detailed description when read in conjunction with the figures and examples, which are exemplary, not limiting.

BRIEF DESCRIPTION OF THE DRAWINGS

The present teachings will become more fully understood from the detailed description and the accompanying drawings, wherein:

FIG. 1 illustrates a g-DLP 3D printer;

FIG. 2A illustrates a resin according to the teachings of the present disclosure with hydrogen bonding between a donor moiety, an acceptor moiety, and a rigid moiety;

FIG. 2B illustrates the resin in FIG. 2A with cross-linking between the donor moiety, the acceptor moiety, and the rigid moiety;

FIG. 3 is a graphical plot of storage modulus and tan δ as a function of temperature for three different grayscale level samples (labeled B1, B2, B3) formed using a resin and g-DLP 3D printing according to the teachings of the present disclosure and using;

FIG. 4 is a graphical plot of shape memory performance of the B1 sample shown in FIG. 3;

FIG. 5 is a graphical plot of shape memory performance of the B2 sample shown in FIG. 3;

FIG. 6 is a graphical plot of stress versus strain for the B1, B2, and B3 samples shown in FIG. 3;

FIG. 7A illustrates a g-DLP 3D printed sample have three grayscale levels (labeled B1, B2, B3);

FIG. 7B illustrates the g-DLP 3D printed sample in FIG. 7A at room temperature (RT) after being cold draw programmed into a new shape at 80° C.;

FIG. 7C illustrates the g-DLP 3D printed sample in FIG. 7B recovered at 50° C.;

FIG. 7D illustrates the g-DLP 3D printed sample in FIG. 7C recovered at 80° C.;

FIG. 7E illustrates the B3 grayscale portion of the g-DLP 3D printed sample in FIG. 7A exhibiting 1000% elastic deformation at RT;

FIG. 8 illustrates a bilayer composite formed from a B1 grayscale layer and a B3 grayscale layer;

FIG. 9 illustrates a heterogeneous hinge module with a B1 grayscale+B3 grayscale hinge exhibiting shape-morphing and recovery according to the teachings of the present disclosure;

FIG. 10 is a graphical plot of fitting experimental data for stress, strain, and temperature as a function of time for a B1 g-DLP 3D printed sample according to the teachings of the present disclosure;

FIG. 11 is a graphical plot of simulated and experimental shape fixity and folding angle as a function of applied strain for a B1 g-DLP 3D printed sample according to the teachings of the present disclosure;

FIG. 12 illustrates a designed and a g-DLP 3D printed hinge module with different amounts of cold draw bending according to the teachings of the present disclosure;

FIG. 13A illustrates a designed and a g-DLP 3D printed hinge module with the g-DLP 3D printed hinge module programmed into a square-shaped configuration according to the teachings of the present disclosure;

FIG. 13B illustrates a designed and a grayscale g-DLP 3D printed hinge module with the g-DLP 3D printed hinge module programmed into an M-shaped configuration according to the teachings of the present disclosure;

FIG. 14A illustrates a designed and a grayscale g-DLP 3D printed hinge module with the g-DLP 3D printed hinge module programmed into a wave-shaped configuration according to the teachings of the present disclosure;

FIG. 14B illustrates a designed and a grayscale g-DLP 3D printed hinge module with the g-DLP 3D printed hinge module programmed into an S-shaped configuration according to the teachings of the present disclosure;

FIG. 15A illustrates a designed g-DLP 3D printed hinge module with hinge portions oriented at a 30 degree angle relative to a length direction according to the teachings of the present disclosure;

FIG. 15B illustrates a g-DLP 3D printed hinge module and an FEA of the design in FIG. 15A with a helical shape having a first pitch; and

FIG. 15C illustrates a g-DLP 3D printed hinge module and an FEA of the design in FIG. 15A with a helical shape having a second pitch.

It should be noted that the figures set forth herein are intended to exemplify the general characteristics of the present technology for the purpose of the description of certain aspects. The figures may not precisely reflect the characteristics of any given aspect and are not necessarily intended to define or limit specific forms or variations within the scope of this technology.

DETAILED DESCRIPTION

The present disclosure provides three dimensional (3D) printed shape-morphing structures, resins for single-vat single cure g-DLP 3D printing of shape-morphing structures, and 3D printing of shape-morphing structures. The shape-morphing structures are monolithic structures that include one or more stretchable soft organogel portions (also referred to herein as “rubbery portion(s)”) and one or more stiff thermoset portions (also referred to herein as “glassy portion(s)”). That is, the single cure resins (also referred to herein simply as “resin” or “resins”) have a composition that provides for g-DLP 3D printed shape-morphing structures that have one or more highly stretchable rubbery portions that exhibit low stiffness and high elasticity and one or more glassy portions that exhibit high stiffness and high strength within a single layer of printing. Accordingly, the use or need of multiple vats of different resins is not needed or required for g-DLP 4D printing of shape-morphing structures according to the teachings of the present disclosure. As used herein, the phrase “4D printing” refers to 3D printing an object or structure that is able to predictably change its shape or properties over time in reaction to conditions such as exposure to water, air, heat, and/or an electric current.

The shape-morphing structures according to the teachings of the present disclosure are cold draw programmable into one or more shapes. As used herein, the phrase “cold draw programmable” refers to a g-DLP 3D printed structure that is or can be formed into a stable shape using a cold draw technique as disclosed herein, and the phrase “stable shape” refers to a shape of a g-DLP 3D printed structure that does do not change when the g-DLP 3D printed structure is at a predefined temperature that is less than a recovery temperature. For example, in some variations shape-morphing g-DLP 3D printed structure according to the teachings of the present disclosure have at least one glassy state portion with a glassy state recovery temperature and at least one rubbery state portion with a rubbery state recovery temperature that is different than the glassy state recovery temperature.

In some variations, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 10 MPa to about 100 MPa. In at least one variation, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 10 MPa to about 200 MPa. In some variations a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 10 MPa to about 300 MPa. And in at least one variation, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 10 MPa to about 400 MPa or from about 10 MPa to about 478 MPa.

In some variations, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 8 MPa to about 100 MPa. In at least one variation, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 5 MPa to about 100 MPa. In some variations a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 2 MPa to about 100 MPa. And in at least one variation, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 1 MPa to about 100 MPa or from about 0.5 MPa to about 100 MPa or from about 0.1 MPa to about 100 MPa.

In some variations, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 5 MPa to about 200 MPa. In at least one variation, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 2 MPa to about 200 MPa. In some variations a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 1 MPa to about 300 MPa. And in at least one variation, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits Young Moduli ranging from about 0.5 MPa to about 400 MPa or from about 0.1 MPa to about 475 MPa.

In some variations, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits an elastic elongation up to 100%. And in some variations, a monolithic structure manufactured with a g-DLP 3D printer using a resin according to the teachings of the present disclosure exhibits an elastic elongation up to 200%, up to 300%, up to 400%, up to 450%, or over 450%, e.g., up to 750% elastic elongation or up to 1000% elongation. Stated differently, a monolithic structure manufactured via g-DLP 3D printing using a resin according to the teachings of the present disclosure has at least one portion with low stiffness and high elasticity and at least one portion with high stiffness and high strength as described in greater detail below.

It should be understood that 3D printing allows for the fabrication of components and structures with geometric and material complexities beyond what is physically and/or economically possible with traditional manufacturing techniques such as casting, machining, cold working, hot working, among others. And new 3D printing capabilities have demonstrated use in functional applications or structures such as deployable structures, soft robotics, flexible electrical components, and biomimetic designs. However, many functional applications such as nature-like structures, airless tires, multi-stable absorbers, and 4D printing require the use of materials with vastly different properties. That is, such structures have or require different portions with very different mechanical and/or physical properties.

It should also be understood that DLP 3D printing is a high-speed and high-resolution printing method that has become increasingly popular in recent years. Digital light processing uses a projector to irradiate hundreds or thousands of thin layers of resin having predefined cross-sections of a solid component such that each thin layer is cured and the solid component is manufactured layer-by-layer. In a typical DLP printing process, a single resin vat is used, only z-direction motion of a build plate is needed to form a component, and photopolymerization (or photocuring) of the thin layers occurs in a few seconds. Accordingly, DLP 3D printing is one of the fastest 3D printing technologies. However, the use of a single resin vat makes DLP in general, not suitable for printing components with multiple material properties. Methods using multiple vats have been developed to print two or more materials by transferring a printed component between multiple vats. However, cross-contamination between multiple vats, switching between different resin vats and cleaning significantly slows down the printing speed.

In g-DLP printing, the local degree of monomer conversion (curing) is controlled by light intensity, which is manipulated at pixel level by an input grayscale image. For example, and with reference to FIG. 1, a g-DLP 3D printer 10 with a projector 100, build platform 120, and a single resin vat 140 containing a resin 150 according to the teachings of the present disclosure is shown. The projector 100 is configured to project a grayscale image onto a transparent bottom wall 142 of the single resin vat 140 such that a layer of the resin 150 having a predefined cross-section of a component 20 with at least one crosslinked stiff thermoset portion 200 and at least one stretchable soft organogel portion 210 is illuminated and cured. After the layer of the resin 150 is illuminated (and cured) via the grayscale exposure from the projector 100, the build platform 120 moves in the +z-direction shown in the figure and the resin 150 flows into or between the mostly cured layer of resin and an upper surface 143 of the transparent bottom wall 142. Then, the projector 100 projects another grayscale image onto the transparent bottom wall 142 of the single resin vat 140 such that the most recent layer of the resin 150 is illuminated with another predefined cross-section of the component 20. The process or cycle continues until manufacture of the component 20, layer-by-layer, is complete.

Referring to FIGS. 2A-2B, one non-limiting example of three monomers included in the resin 150 in the resin are shown. Particularly, the resin 150 includes at least one hydrogen bond donating monomer 152 (2-hydroxyethyl acrylate shown in the figures), at least one hydrogen bond accepting monomer 154 (aliphatic urethane-based diacrylate shown in the figures), and at least one rigid monomer 156 (isobornyl acrylate shown in the figures). In some variations, the at least one hydrogen bond donating monomer 152 can also be a hydrogen bond accepting monomer that is different than the at least one hydrogen bond accepting monomer 154 and/or the least one hydrogen bond accepting monomer 154 can also be a hydrogen bond donating monomer that is different than the at least one hydrogen bond donating monomer 152.

In some variations, the at least one hydrogen bond donating monomer 152 (also referred to herein as “donator moiety 152”) is an acrylate monomer with one or more a side groups that include a free carbonyl (—C═O) group or primary, secondary, or tertiary amine side group on an acrylate. And in at least one variation, the at least one hydrogen bond accepting monomer 154 (also referred to herein as “acceptor moiety 154”) is an acrylate monomer with one or more side groups that include a free hydroxy (—OH), a primary or secondary amine (—N(H)—, e.g., a urethane (C(O)—N(H)—), or an imine (—N═). And the at least one rigid monomer 156 (also referred to herein as “rigid moiety 156”) can be an acrylate monomer with one or more side groups that include one or more of cyclohexyls, substituted cyclohexyls, bicyclic side groups such as isobornyl, norbornyl, and dicylcopentanyl, among others. In addition, the donator moiety 152 and/or the acceptor moiety 154 is an oligomer (e.g., aliphatic urethane-based diacrylate) that functions as crosslinker.

Non limiting examples of the at least one hydrogen bond donating monomer 152 include 2-hydroxyethyl acrylate (2-HEA), caprolactone acrylate, hydroxypropyl acrylate, 2,3-dihydroxypropyl acrylate, 1,3-dihydroxypropyl acrylate, N-hydroxyethyl acrylamide, and aliphatic urethane-based diacrylate. Non-limiting examples of the at least one hydrogen bond acceptor monomer 154 include aliphatic urethane-based diacrylate (AUD) and 2-HEA. And non-limiting examples of the at least one rigid monomer 156 include isobornyl acrylate (IOBA), 4-acryloylmorpholine, methyl methacrylate, 2-hydroxyethyl methacrylate, and isobornyl methacrylate.

In some variations, resins according to the teachings of the present disclosure (also referred to herein simply as “resin 150”) include between about 5 weight percent (wt %) and about 35 wt % of the at least one hydrogen bond donator monomer 152, and in at least one variation the resin 150 includes between about 10 wt % and about 30 wt % of the least one hydrogen bond donator monomer 152. And in some variations, the resin 150 includes between about 15 wt % and about 25 wt % of the least one hydrogen bond donator monomer 152. For example, in at least one variation the resin 150 includes about 20 wt % of the least one hydrogen bond donator monomer 152.

In some variations the resin 150 includes between about 5 wt % and about 35 wt % of the at least one hydrogen bond acceptor monomer 154, and in at least one variation the resin 150 includes between about 10 wt % and about 30 wt % of the least one hydrogen bond acceptor monomer 154. And in some variations, the resin 150 includes between about 15 wt % and about 25 wt % of the least one hydrogen bond acceptor monomer 154. For example, in at least one variation the resin 150 includes about 20 wt % of the least one hydrogen bond acceptor monomer 154.

In some variations the resin 150 includes between about 45 wt % and about 75 wt % of the at least one rigid monomer 156, and in at least one variation the resin 150 includes between about 50 wt % and about 70 wt % of the least one rigid monomer 156. And in some variations, the resin 150 includes between about 55 wt % and about 65 wt % of the least one rigid monomer 156. For example, in at least one variation the resin 150 includes about 60 wt % of the least one rigid monomer 156.

In some variations, the resin 150 includes a photoinitiator. For example, in some variations the resin includes between about 0.1 wt % and about 2 wt % of the photoinitiator, for example between about 0.4 wt % and 1.6 wt % of the photoinitiator or between about 0.7 wt % and about 1.3 wt % of the photoinitiator. In at least one variation the resin 150 includes about 1.0 wt % of the photoinitiator. Non-limiting examples of the photoinitiator include photoinitiator 819 (phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide) and camphorquinone.

In some variations, the resin 150 includes a photoabsorber. For example, in some variations the resin includes between about 0.01 wt % and about 1 wt % of the photoabsorber, for example between about 0.025 wt % and 0.5 wt % of the photoabsorber or between about 0.04 wt % and about 0.1 wt % of the photoabsorber. In at least one variation the resin 150 includes about 0.05 wt % of the photoabsorber. Non-limiting examples of the photoabsorber include methylene, coccine, and tartrazine.

In an effort to better describe the resin 150, its properties, and its capabilities for manufacturing monolithic shape-morphing structures with a range of properties, and yet not to limit the scope of the present disclosure in any manner, one example composition of the resin 150 and numerous examples of monolithic shape-morphing structures and corresponding properties are discussed below.

The resin 150 was prepared by mixing monomers of 2-hydroxyethyl acrylate (Sigma-Aldrich, MO, USA), isobornyl acrylate (Sigma-Aldrich), and AUD (Ebecryl 8413, Allnex, GA, USA) with a weight ratio of 20:60:20. Then, 1 wt % photoinitiator (Irgacure 819, Sigma-Aldrich) and 0.05 wt % photo absorber (Sudan I, Sigma Aldrich) were added to the mixture of monomers.

Not being bound by theory, the IBOA and 2-HEA were included as linear chain builders and AUD as a crosslinker. The AUD is a viscous oligomer with high molecular weight aliphatic chains and urethane units, and forms H—N . . . O hydrogen bonds when interacting with 2-HEA and IOBA monomers. Also, the 2-HEA provides abundant —OH groups that form additional O—H . . . O hydrogen bonds.

At a low degree of curing (also known as “degree of cure” and referred to herein as “DoC”), the covalent network with the prevalent hydrogen bonds of the cured resin provides high stretchability in a rubbery state as illustrated in FIG. 2A, while at high DoC, the stiff IBOA exhibits a glass transition temperature (T_g) above room temperature as illustrated in FIG. 2B, thereby yielding glassy behaviors with high moduli.

Referring to FIGS. 3-6, test results are shown for g-DLP 3D printed samples formed from the resin 150 in a bottom-up DLP printer where light was projected from the bottom of the vat. The bottom-up DLP printer employed a 385 nm UV-LED light projector (PR04500, Wintech Digital Systems Technology Corp., Carlsbad, CA, USA) and a linear translation stage (LTS150 Thorlabs, Newton, NJ, USA). A container with an oxygen-permeable window (Teflon AF-2400, Biogeneral Inc., CA, USA) was used as the resin vat.

Designs of the g-DLP 3D printed samples were sliced into image files with a thickness of 0.05 mm and then converted into grayscaled image files with a MATLAB script. The continuous liquid interface production (CLIP) approach was utilized at the optimized speed of 3 s/layer to print the designed 3D structures. The light intensity of the printer was calibrated with a photometer (ILT1400-A Radiometer, International Light Technologies Inc., MA, USA) before printing.

In one set of tests, three g-DLP 3D printed samples were formed from the resin 150 using three grayscale levels. Particularly, two g-DLP 3D printed samples were formed using two different high degree of curings (DoCs) and one g-DLP 3D printed sample was formed using a low level DoC. That is, each g-DLP 3D printed sample was formed using a single DoC such that testing of the resin 150 g-DLP 3D printed using three different DoCs was performed.

Referring specifically to FIG. 3, the thermomechanical properties of the three g-DLP 3D printed samples with the three different DoCs were evaluated with dynamic mechanical analyses (DMA). The two g-DLP 3D printed samples formed using the two high DoCs (labeled B1 and B2) resulted in glassy states at room temperature with distinct glass transition temperatures (Tg) of 87° C. and 66° C., respectively. By comparison, the sample formed using the low DoC (labeled B3) resulted in an organogel state with a much lower Tg of −14° C. In addition, the three g-DLP 3D printed samples exhibited typical thermoset behaviors with a rapid drop of storage modulus above the Tg to a crosslinked rubbery plateau. For example, the B1 and B2 samples were both glassy thermosets at room temperature with the B2 component starting to transition to a soft and rubbery state at about 50° C., while the B1 component remained in the glassy state until about 75° C.

Referring now to FIGS. 4 and 5, shape-memory (SM) cyclic testing was performed to examine the shape-memory behavior of the B1 sample (FIG. 4) and the B2 sample (FIG. 5). Both samples were subjected to 100% strain (ε_p) at a programming temperature of 100° C. and then cooled to 25° C. The load used to strain the samples was then removed such that a temporarily fixed strain ε_T and a shape fixing ratio ‘ε_T/ε_p’ were obtained. The temperature was then gradually increased from 25° C. to activate free recovery of the strained (deformed) samples and a shape recovery ratio ‘(ε_T−ε_R)/ε_T’ was calculated after measuring a recovered strain ER. The glassy states of the B1 and B2 samples exhibited excellent shape fixing ratios of 96.9% and 95.8%, respectively, and shape recovery ratios of 100% (for B1 and B2) under the large deformation. And with reference to FIG. 6, the strain-stress behaviors of the B1, B2, and B3 samples were measured using uniaxial tensile tests with the B1 and B2 samples displaying typical glassy and ductile behavior, and the B3 sample displaying soft and stretchable behavior.

To verify the g-DLP as a feasible platform for 4D printing, and with reference to FIG. 7A, a strip sample with two glassy ends (B1 and B2) and a rubbery middle section (B3) was g-DLP 3D printed for programming and recovery testing. Particularly, the two glassy B1, B2 ends were programmed (bent) at 80° C. and fixed in place as illustrated in FIG. 7B by rapid cooling the strip sample in an ice bath. The strip sample was placed into a 50° C. water bath where the B2 end shifted (recovered) to its original shape as illustrated in FIG. 7C, and then the water bath temperature was increased to 80° C. which resulted in the B1 end returning to its original shape (FIG. 7D). In addition, the rubbery middle section B3 was successfully stretched 1000% and recovered at room temperature (i.e., about 22° C.) as illustrated in FIG. 7E.

Referring now to FIG. 8, a classical mechanical actuated bilayer structure 30 composed of a B1 layer and B3 layer is shown with the rubbery B3 layer undergoing recoverable elastic strain and the glassy B1 layer undergoing unrecoverable plastic strain when the bilayer structure 30 is strained in the z-direction shown in the figure. And as illustrated in FIG. 8, the mismatch of strain recovery between the B1, B3 bilayer composite results in a bending deformation in the y-direction shown in the figure.

Referring to FIG. 9, and based on the classical actuated bilayer mechanism 30 illustrated in FIG. 8, a g-DLP platform to print a heterogeneous hinge module 40 with glassy B1 fibers (labeled Bit) embedded in a rubbery B3 matrix (labeled B3_m and also referred to herein as a “rubbery state matrix”) was developed (the B3_m matrix in the perspective drawings/figures is illustrated as transparent for clarity). Particularly, the heterogeneous hinge module 40 (also referred to herein simply as “hinge module 40”) included a pair of B1 ends (also referred to herein as “glassy state portions” or “glassy state ends”) and a middle or hinge B1_f, B3_m portion (also referred to herein as a “heterogeneous portion”) disposed between the B1 ends. And unlike the bilayer structure 30 shown in FIG. 8, the hinge module 40 was stretchable at room temperature using low external forces.

Not being bound by theory, a folding angle ‘θ_f’ (not shown in FIG. 9) of the hinge module 40 depends on the mechanical properties and geometric designs of the two constituent materials (i.e., hinge dimensions, fiber position and dimensions, etc.) and an analytical model for the folding θ_f angle of the hinge module 40, based on those parameters, can be expressed as:

$\begin{array}{cc}{\theta }_f=\kappa l_H\left(1+{\epsilon }_{\mathrm{NP}}\right)& \left(1\right)\end{array}$

where κ is the bending curvature, l_H is the length of the hinge, and ε_NP is the axial strain (perpendicular to cross-section) of a neutral plane due to force balance represented by:

$\begin{array}{cc}{\epsilon }_{\mathrm{NP}}=\frac{E_f{A}_f}{E_f{A}_f+E_m{A}_m}{\epsilon }_{\mathrm{fix}}& \left(2\right)\end{array}$

where E_f and E_m denote the Young's modulus of the fiber and matrix, A_f and A_m the total area of the fiber and matrix in the cross-section, respectively, and ε_fix denotes the residual strain of glassy fiber due to stretch. Note that the neutral plane has zero longitudinal strain due to the bending deformation. In addition, using the Euler-Bernoulli beam theory, the bending curvature K can be derived as:

$\begin{array}{cc}\kappa =\frac{E_m{A}_m\left({\stackrel{\_}{y}}_m-{\stackrel{\_}{y}}_f\right){\epsilon }_{\mathrm{NP}}}{E_f{I}_{\mathrm{NP}-A_f}+E_m{I}_{\mathrm{NP}-A_m}}& \left(3\right)\end{array}$

where y_f and y_m are the area-mean y position of the fiber and matrix, respectively, and I_NP-f and I_NP-m are the second area moment of the fiber and matrix with respect to the neutral plane, respectively.

It should be understood that the analytical prediction of the folding angle θ_f relies on ε_fix as an explicit function of an applied strain (ε_app) and the visco-plasticity of a given material, which is hard to obtain for some or all of the materials disclosed herein due to the complex constitutive behavior of, e.g., the glassy B1 material. However, an empirical form can be obtained by fitting experimental data for a given material. For example the empirical relation ε_fix=−0.27ε_app²+0.51ε_app+0.71 was obtained by fitting the experimental data for the B1 material shown in FIG. 10. And using this empirical formula and Eqs.(1)-(3), the theoretical prediction of the strain-angle relation achieves good agreement with finite element analysis (FEA) and experiment as shown in FIG. 11.

Referring now to FIG. 12, a g-DLP 3D printed structure 50 with B1_f, B3_m hinge portion disposed between B1 end portions was manufactured per a design 50d and programmed at different angles as shown in the figure. And as observed in FIG. 12, the programmed angles agreed well with FEA modeling of the design 50d and the robust multi-properties provided by the g-DLP printing platform provided a fully folded shape change (with a strain of ˜120%) of the g-DLP 3D printed structure 50. Again, the B3_m matrix of the B1_f, B3_m hinge portion is shown as transparent for clarity.

It should be understood that this understanding of the underlying mechanics principles enables a general design rationale for complex shape-morphing structures. That is, combining the programmable cold-draw hinge modules with stiff end portions enables the manufacture of complex shape-shifting structures. Furthermore, as mentioned above, the glassy state part demonstrates excellent shape memory performance with reversible plasticity at elevated temperatures. Thus, the deformation of the hinge modules is also reversible which enables the reconfigurability of the printed structures over numerous cycles.

For example, and with reference to FIGS. 13A-13B, a strip sample 60 (g-DLP 3D printed per the design 60d) with B1_f, B3_m hinge portions disposed between B1 end portions (also referred to herein as “glassy state portions”), and with the B1_f fibers (also referred to herein as “glassy state fibers”) on an upper surface (+y direction) of all the B1_f, B3_m hinge portions is shown in FIG. 13A. And a strip sample 62 (g-DLP 3D printed per the design 62d) with B1_f, B3_m hinge portions disposed between B1 end portions with the B1_f fibers on a lower surface (+x direction) of the middle B1_f, B3_m hinge portion (i.e., the central B1_f, B3_m hinge portion between the two outer B1_f, B3_m hinge portions having the B1_f fibers on the upper surface) is shown in FIG. 13B. In addition, the g-DLP 3D printed structure 60 in FIG. 13A was reversibly programmed into a square shape while the g-DLP 3D printed structure 62 in FIG. 13B was reversibly programmed into an M shape via cold draw morphing at 80° C. followed by cooling to room temperature.

For another example, and with reference to FIGS. 14A-14B, a strip sample 70 (g-DLP 3D printed per the design 70d) with B1_f, B3_m hinge portions disposed between B1 end portions, and with the B1_f fibers on a lower surface (−x direction) of four (4) of the B1_f, B3_m hinge portions shown within the dotted line rectangle and between a pair of four B1_f, B3_m hinge portions is shown in FIG. 14A. And with such a configuration, the strip sample 70 was programmed into a wave shape that agreed with an FEA (labeled ‘70f’) of the design 70d. In addition, a strip sample 72 (g-DLP 3D printed per the design 72d) having the same number of B1 end portions and B1_f, B3_m hinge portions the strip sample 70, but with B1_f fibers on a lower surface (−x direction) of six (6) B1_f, B3_m hinge portions within the dotted line rectangle and disposed between B1 end portions on the right hand side (+y direction) of the strip sample 72 is shown in FIG. 14B. And with such a configuration, the strip sample 72 was programmed into an S shape that agreed with an FEA (labeled ‘72f’) of the design 72d.

And for still another example, and with reference to FIGS. 15A-15C, a strip sample design 80d with B1_f, B3_m hinge portions disposed between B1 end portions at an angle of 30° relative to the length direction (x-axis) of the design 80d is shown in FIG. 15A. In addition, a strip sample 80a (g-DLP 3D printed per the design 80d) programmed into a helix with a first pitch is shown in FIG. 15B and a strip sample strip sample 80b (g-DLP 3D printed per the design 80d) programmed into a helix with a second pitch different than the first pitch is shown in FIG. 15C. Accordingly, the two dimensional strip samples 80a, 80b were programed with out-of-plane bending that resulted in a collective twist of the structure into strip samples 80a, 80b with 3D helix shapes. Furthermore, the pitch of the strip samples 80a, 80b was controlled by varying the applied strain and the corresponding FEA simulations 80af, 80bf based on the heterogeneous hinge structures (i.e., B1_f, B3_m hinge portions) were in good agreement with the actual programming and demonstrated accurate angle and direction control of cold-draw shape morphing capability.

The preceding description is merely illustrative in nature and is in no way intended to limit the disclosure, its application, or uses. As used herein, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical “or.” It should be understood that the various steps within a method may be executed in different order without altering the principles of the present disclosure. Disclosure of ranges includes disclosure of all ranges and subdivided ranges within the entire range.

The headings (such as “Background” and “Summary”) and sub-headings used herein are intended only for general organization of topics within the present disclosure and are not intended to limit the disclosure of the technology or any aspect thereof. The recitation of multiple forms or variations having stated features is not intended to exclude other forms or variations having additional features, or other forms or variations incorporating different combinations of the stated features.

As used herein the terms “about” and “generally” when related to numerical values herein refers to known commercial and/or experimental measurement variations or tolerances for the referenced quantity. In some variations, such known commercial and/or experimental measurement tolerances are +/−10% of the measured value, while in other variations such known commercial and/or experimental measurement tolerances are +/−5% of the measured value, while in still other variations such known commercial and/or experimental measurement tolerances are +/−2.5% of the measured value. And in at least one variation, such known commercial and/or experimental measurement tolerances are +/−1% of the measured value.

As used herein, the terms “comprise” and “include” and their variants are intended to be non-limiting, such that recitation of items in succession or a list is not to the exclusion of other like items that may also be useful in the devices and methods of this technology. Similarly, the terms “can” and “may” and their variants are intended to be non-limiting, such that recitation that a form or variation can or may comprise certain elements or features does not exclude other forms or variations of the present technology that do not contain those elements or features.

The broad teachings of the present disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the specification and the following claims. Reference herein to one aspect, or various aspects means that a particular feature, structure, or characteristic described in connection with a form or variation is included in at least one form or variation. The appearances of the phrase “in one variation” or “in one form” (or variations thereof) are not necessarily referring to the same form or variation. It should also be understood that the various method steps discussed herein do not have to be carried out in the same order as depicted, and not each method step is required in each form or variation.

The foregoing description of the forms or variations has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular form or variation are generally not limited to that particular form or variation, but, where applicable, are interchangeable and can be used in a selected form or variation, even if not specifically shown or described. The same may also be varied in many ways. Such variations should not be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

While particular forms or variations have been described, alternatives, modifications, variations, improvements, and substantial equivalents that are or may be presently unforeseen may arise to applicants or others skilled in the art. Accordingly, the appended claims as filed and as they may be amended, are intended to embrace all such alternatives, modifications variations, improvements, and substantial equivalents.

Claims

1. A shape-morphing structure comprising: a cold draw programmable grayscale digital light processing (g-DLP) 3D printed unitary hinge component comprising at least one glassy state portion and at least one rubbery state portion.

2. The shape-morphing according to claim 1, wherein the at least one glassy state portion has a glassy state recovery temperature and the at least one rubbery state portion has a rubbery state recovery temperature different than the glassy state recovery temperature.

3. The shape-morphing according to claim 1, wherein the at least one rubbery state portion has a rubbery state recovery temperature and the at least one glassy state portion comprises a first glassy state portion with a first glassy state recovery temperature that is different than the rubbery state recovery temperature and a second glassy state portion with a second glassy state recovery temperature that is different than the first glassy state recovery portion and the rubbery state recovery temperature.

4. The shape-morphing according to claim 1, wherein the at least one rubbery state portion is disposed between and unitary with at least two glassy state portions.

5. The shape-morphing according to claim 1, wherein the at least one rubbery state portion comprises a heterogeneous portion with a rubbery state matrix and glassy state fibers disposed within the rubbery state matrix.

6. The shape-morphing according to claim 5, wherein the heterogeneous portion is disposed between and unitary with a pair of glassy state portions, and the pair of glassy state portions are homogeneous portions.

7. The shape-morphing structure according to claim 1, wherein the g-DLP 3D printed unitary hinge component is formed from a resin comprising: a donor moiety in the form of an acrylate monomer with a side group comprising at least one of a free carbonyl, a primary amine on an acrylate, a secondary amine on an acrylate, and a tertiary amine on an acrylate;an acceptor moiety different than the donor moiety and in the form of an acrylate monomer with a side group comprising at least one of a free hydroxy, a primary amine, secondary amine, and an imine; anda rigid moiety in the form of an acrylate monomer with a side group comprising of one or more of a cyclohexyl, a substituted cyclohexyl, and a bicyclic structure.

8. The shape-morphing structure according to claim 7, wherein one of the donor moiety and the acceptor moiety is an oligomer crosslinker.

9. The shape-morphing structure according to claim 7, wherein the donor moiety is selected from at least one of 2-hydroxyethyl acrylate, caprolactone acrylate, hydroxypropyl acrylate, 2,3-dihydroxypropyl acrylate, 1,3-dihydroxypropyl acrylate, N-hydroxyethyl acrylamide, and aliphatic urethane-based diacrylate.

10. The shape-morphing structure according to claim 9, wherein the acceptor moiety is selected from at least one of aliphatic urethane-based diacrylate and 2-hydroxyethyl acrylate.

11. The shape-morphing structure according to claim 10, wherein the rigid moiety is selected from at least one of isobornyl acrylate, 4-acryloylmorpholine, methyl methacrylate, 2-hydroxyethyl methacrylate, and isobornyl methacrylate.

12. The shape-morphing structure according to claim 11, wherein: the donor moiety is between about 10 wt. % to about 30 wt. % of an overall composition of the resin;the acceptor moiety is between about 10 wt. % to about 30 wt. % of an overall composition of the resin; andthe rigid moiety is between about 50 wt. % to about 70 wt. % of an overall composition of the resin.

13. The shape-morphing structure according to claim 9, wherein: the donor moiety is selected from the group consisting of 2-hydroxyethyl acrylate, caprolactone acrylate, hydroxypropyl acrylate, 2,3-dihydroxypropyl acrylate, 1,3-dihydroxypropyl acrylate, N-hydroxyethyl acrylamide, and aliphatic urethane-based diacrylate;the acceptor moiety is selected from the group consisting of aliphatic urethane-based diacrylate and 2-hydroxyethyl acrylate; andthe rigid moiety is selected from the group consisting of isobornyl acrylate, 4-acryloylmorpholine, methyl methacrylate, 2-hydroxyethyl methacrylate, and isobornyl methacrylate.

14. The shape-morphing structure according to claim 13, wherein: the donor moiety is between about 10 wt. % to about 30 wt. % of an overall composition of the resin;the acceptor moiety is between about 10 wt. % to about 30 wt. % of an overall composition of the resin; andthe rigid moiety is between about 50 wt. % to about 70 wt. % of an overall composition of the resin.

15. The shape-morphing structure according to claim 1, wherein the g-DLP 3D printed unitary hinge component is formed from a resin comprising: between about 10 wt. % and about 30 wt. % of a donor moiety in the form of 2-hydroxyethyl acrylate;between about 10 wt. % and about 30 wt. % of an acceptor moiety in the form of aliphatic urethane-based diacrylate; andbetween about 50 wt. % to about 70 wt. % of a rigid moiety in the form of isobornyl acrylate.

16. A shape-morphing structure comprising: a cold draw programmable grayscale digital light processing (g-DLP) 3D printed unitary hinge component formed from a resin and comprising at least one glassy state portion and at least one rubbery state portion, the resin comprising: a donor moiety in the form of an acrylate monomer with a side group comprising at least one of a free carbonyl, a primary amine on an acrylate, a secondary amine on an acrylate, and a tertiary amine on an acrylate;an acceptor moiety different than the donor moiety and in the form of an acrylate monomer with a side group comprising at least one of a free hydroxy, a primary amine, secondary amine, and an imine; anda rigid moiety in the form of an acrylate monomer with a side group comprising of one or more of a cyclohexyl, a substituted cyclohexyl, and a bicyclic structure.

17. The shape-morphing according to claim 16, wherein the at least one glassy state portion has a glassy state recovery temperature and the at least one rubbery state portion has a rubbery state recovery temperature different than the glassy state recovery temperature.

18. The shape-morphing according to claim 17, wherein the at least one glassy state portion comprises a first glassy state portion with a first glassy state recovery temperature that is different than the rubbery state recovery temperature and a second glassy state portion with a second glassy state recovery temperature that is different than the first glassy state recovery portion and the rubbery state recovery temperature.

19. A shape-morphing structure comprising: a cold draw programmable grayscale digital light processing (g-DLP) 3D printed unitary hinge component formed from a resin and comprising at least one glassy state portion with a glassy state recovery temperature and at least one rubbery state portion with a rubbery state recovery temperature different than the glassy state recovery temperature, the resin comprising: a donor moiety in the form of an acrylate monomer with a side group comprising at least one of a free carbonyl, a primary amine on an acrylate, a secondary amine on an acrylate, and a tertiary amine on an acrylate;an acceptor moiety different than the donor moiety and in the form of an acrylate monomer with a side group comprising at least one of a free hydroxy, a primary amine, secondary amine, and an imine; anda rigid moiety in the form of an acrylate monomer with a side group comprising of one or more of a cyclohexyl, a substituted cyclohexyl, and a bicyclic structure.

20. The shape-morphing according to claim 19, wherein the at least one glassy state portion comprises a first glassy state portion with a first glassy state recovery temperature that is different than the rubbery state recovery temperature and a second glassy state portion with a second glassy state recovery temperature that is different than the first glassy state recovery portion and the rubbery state recovery temperature.