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Additive Manufacturing-Facilitated Blow Molding for Functional Thin-Walled Polymeric Structures

Junyu Chen, Dotan Ilssar, Dennis M. Kochmann

Abstract

Thin-walled structures capable of large, reversible deformation are key to multistable structures, origami, kirigami, and soft robotics. However, conventional fabrication techniques, including 3D printing, casting, and laser cutting, suffer from poor surface quality, low durability, complex processing steps, and restricted geometric freedom, hindering the repeatable production of thin-walled, continuous structures. Here, an additive manufacturing-facilitated blow molding (AM-BM) approach is introduced, combining the design flexibility of additive manufacturing with the robustness of blow molding. By replacing metal molds with 3D-printed resin ones, AM-BM enables rapid, low-cost fabrication of thin-walled polymeric components with tunable geometry and controllable wall thickness across diverse thermoplastic materials. The thickness control allows thin-walled components to function either as rigid load-bearing elements or as compliant hinges that permit reversible deformation. The versatility of AM-BM is demonstrated through representative examples: multistable structures with geometry-controlled buckling and rich reconfigurability; origami and kirigami structures with extensive design freedom, scalable complexity, and uniform mechanical properties; and soft actuators and robots with ultrahigh load-to-weight ratios, rapid response, and scalable design. Altogether, AM-BM provides an efficient and versatile method for creating thin-walled structures that combine geometric freedom, mechanical functionality, and scalable production.

Additive Manufacturing-Facilitated Blow Molding for Functional Thin-Walled Polymeric Structures

Abstract

Thin-walled structures capable of large, reversible deformation are key to multistable structures, origami, kirigami, and soft robotics. However, conventional fabrication techniques, including 3D printing, casting, and laser cutting, suffer from poor surface quality, low durability, complex processing steps, and restricted geometric freedom, hindering the repeatable production of thin-walled, continuous structures. Here, an additive manufacturing-facilitated blow molding (AM-BM) approach is introduced, combining the design flexibility of additive manufacturing with the robustness of blow molding. By replacing metal molds with 3D-printed resin ones, AM-BM enables rapid, low-cost fabrication of thin-walled polymeric components with tunable geometry and controllable wall thickness across diverse thermoplastic materials. The thickness control allows thin-walled components to function either as rigid load-bearing elements or as compliant hinges that permit reversible deformation. The versatility of AM-BM is demonstrated through representative examples: multistable structures with geometry-controlled buckling and rich reconfigurability; origami and kirigami structures with extensive design freedom, scalable complexity, and uniform mechanical properties; and soft actuators and robots with ultrahigh load-to-weight ratios, rapid response, and scalable design. Altogether, AM-BM provides an efficient and versatile method for creating thin-walled structures that combine geometric freedom, mechanical functionality, and scalable production.
Paper Structure (8 sections, 2 equations, 4 figures)

This paper contains 8 sections, 2 equations, 4 figures.

Table of Contents

  1. Introduction
  2. Results and discussion
  3. Overview of additive manufacturing-facilitated blow molding
  4. Multistable structure
  5. Tubular Origami and Kirigami
  6. Soft robotic actuators
  7. Conclusion
  8. Experimental Section

Figures (4)

  • Figure 1: Fabrication process and demonstration of AM-BM. (a) Schematic illustration of the AM-BM fabrication process and potential applications. (b) Relation between mold radius $R_2$ and resulting wall thickness $t_2$. (c-e) Measured torque response of (c) convex hinges with different vertex radii, (d) convex hinges with different arc radii, and (e) concave hinges with different angles (the inset schematics are the cross-section views of blow-molded hinges, the 3D view is shown in Figure S1, Supporting Information, the red dots denote the central axes, the purple regions represent the expanded thermoplastic material, and the gray regions indicate the mold; shaded envelopes in the data plots show standard deviations of 3 tests). (f) Bellows fabricated from different thermoplastic materials (scale bar: 10 mm). (g) Multistable structures of various sizes (scale bar: 10 mm). (h,i) Cyclic durability tests of (h) a multistable structure and (i) a bellow (scale bar: 10 mm).
  • Figure 2: Multistable structures. (a) Micrographs of the cross-section of a multistable conical shell in the deployed (left) and folded (right) configurations (scale bar: 1 mm). (b) Multistable structure in the deployed (left), folded (middle), and bent (right) stable configurations. (scale bar: 10 mm) (c,d) Reconfiguration of a multistable structure into (c) a 3D "ETH" and (d) a double-helix shape. (e) Force–displacement response of a single multistable unit cell. (f–h) Variation of the critical buckling forces $F_\text{cr,t/c}$ with design parameters of the conical shell: (f) tilting angle $\alpha$, (g) width $w$, and (h) outer radius $R$. (i) Force–displacement relation of a straw made of five multistable unit cells with different critical buckling forces connected in series. (j) Sequential reconfiguration of the multistable structure from the “00000” to “10101” state (scale bar: 10 mm; see also Video S2, Supporting Information).
  • Figure 3: Origami and kirigami (scale bars: 10 mm). (a–e) Designs of different origami and kirigami patterns, where black lines denote mountain folds and blue lines denote valley folds: (a) Waterbomb, (b) Kresling 1, (c) Kresling 2, (d) Accordion, and (e) Yoshimura. (f) A waterbomb origami with 496 unit cells. (g) Modified Yoshimura origami design. (h) Pneumatic origami actuator (based on the adapted Yoshimura design) under zero (left), positive (middle), and negative (right) gauge pressure $\Delta P$. (i–l) Origami gripper grasping different objects: (i) a ball, (j) a glass, (k) a ring light, and (l) a "C"-shaped object. (m) Three-point bending test setup for the tubular kirigami structures. (n,o) Normalized three-point bending test results at different orientations for (n) laser-cut kirigami and (o) AM-BM-fabricated kirigami.
  • Figure 4: Soft robotic systems fabricated using AM-BM (scale bars: 10 mm). (a–e) Pneumatic artificial muscle. (a) Working principle of the artificial muscle. (b) Strain–pressure relation under a 1 kg load. (c) Force–pressure relationship with both ends fixed. (d) Unactuated state supporting a 7 kg payload. (e) Actuated state with a 7 kg payload. (f–i) Soft robotic arm. (f) Actuation under zero (left), negative (middle), and positive (right) gauge pressure $\Delta P$. (g) Demonstration of the arm’s workspace. (h) Hexagonal trajectory achieved through combined bending and rotation. (i) Lifting of a 5 kg load. (j–r) Bionic robotic hand. (j) Design of an individual bending joint. (k–o) Representative gestures including (k) number "1", (l) number "2", (m) number "3", (n) fully open palm, and (o) closed fist. (p–r) Grasping different objects, including (p) a ball, (q) a bottle, and (r) a roll of tape.