4D Printing: Towards Biomimetic Additive Manufacturing
2013 Tsai, E., MS thesis, MIT,
State of the art additive-manufacturing platforms typically utilize a wide variety of materials and combinations of materials to 3D print objects with complex geometries. Typically necessitated by the fabrication process itself, such objects are fabricated in a layer-by-layer method (Levy, Schindel, & Kruth, 2003). Although some work has been done towards heterogeneous object modeling in layered manufacturing (Patil, Dutta, Bhatt, Jurrens, Lyons, & Pratt, 2002), variations in bulk material properties or anisotropies of the object are often byproducts of the fabrication itself (Ahn, Montero, Odell, Roundy, & Wright, 2002) (Cooke, Tomlinson, Burguete, Johns, & Vanard, 2011). Currently, the most accessible approaches to the fabrication of designed anisotropy are achieved through the introduction of spatial non-uniformity in material composition (Oxman, Keating, & Tsai, 2011). Tangible examples include the optimization of cellular material distributions and density in response to loading patterns on the architectural scale as well as geometrical and material gradients of varying elasticity on product scale applications (Oxman, Tsai, & Firstenberg, 2012). Such efforts enable the user to design, control and modulate properties across spatial and temporal scales, designing both material and organization. In moving towards the nexus of biomimetic fabrication and additive manufacturing, several limitations arise in prototyping with current methods and materials. Static objects with no functional variation across directions, distances or time fail to capture many of the intricacies inherent across different scales in Nature’s designs. As concrete examples: orthoses and prostheses intended to interface intimately with the human form embody intricate geometries yet are typically composed of a number of homogenous materials. Given that the shape and volume of human limbs fluctuate during each step and throughout different levels of activity due in part to muscle contractions and other forces there is real need for artifacts that are able to comfortably accommodate this broad range of movements. This thesis introduces the term “4D printing” addresses the rapid fabrication of artifacts with one or more additional design dimensions. In particular, 4D printing is defined as the fabrication of objects through the deposition of a material using a print head, nozzle, or other printer technology where the objects contain one or more additional design dimension, such as material gradation over distance or direction, response or adaptation over time, or controlled anisotropy throughout volume.