Murialdo Maxwell | 19-LW-056
Four-dimensional (4D) printing adds a new dimension to additive manufacturing, specifically, the ability for an object to transform its shape after it has been printed. These prints are often comprised of shape memory polymers, which are actuated by heating, sometimes using resistive heating from electric currents through the filament. However, the applications of 4D prints have been limited by the crudeness of their actuation methods. Controllably actuating only specific regions of a 4D print using internal mechanisms (e.g., electrical resistive heating) has proven challenging. Nevertheless, the precise signal control offered by percolating electronics would exponentially amplify the versatility of 4D prints by allowing for complex, origami-inspired transformations of fully printed parts, orchestrated in real time.
We investigated a new paradigm for controlling the actuation of a 4D print using internally propagated signals. This new approach (i.e., percolating electronics) entails mixing micron-scale, high-aspect-ratio active electronics components known as chiplets into 4D-printable feedstock inks prior to printing. The active electronics are designed to form randomly percolating electrical pathways within the feedstock ink itself. These electrical pathways have built-in logic components that allow an operator to selectively address and actuate individual regions of a 4D-printed object in real time, without the need for post-processing.
In this project we conceptualized, designed, fabricated, characterized, and tested the fundamental components necessary for signal control by percolating electronics. Our steps included (1) simulating high-aspect-ratio chiplets subjected to the shear flows present in a non-Newtonian ink extruded by direct-ink-write (DIW) printing; (2) designing and simulating a finite-state-machine (FSM) circuit to control each chiplet; (3) fabricating and testing this complementary metal-oxide-semiconductor (CMOS) circuit; (4) fabricating over one million chiplets on silicon wafers; (5) developing and implementing a chiplet-release protocol; (6) characterizing the chiplets; and (7) studying the printability of mock-chiplet-loaded inks. These experiments indicate the viability of using signal control of percolating electronics for numerous applications.
This project builds on Lawrence Livermore National Laboratory's core competency in advanced materials and manufacturing. The percolating electronics signal control paradigm studied in this project can be applied to (co-printed with) many advanced printable inks developed at the Laboratory and elsewhere, including reactive/energetic inks, gas-absorbing inks, biological-substrate inks, catalysis-substrate inks, color-changing inks, and porous inks. Potential applications of the technology include medical devices, wearables, soft robotics, adaptive packaging, self-assembling structures, custom adaptive parts, tunable mechanical properties, and safety controls.
Publications, Presentations, and Patents
Maxwell Murialdo, Y. Kanarska, and Andrew Pascall. 3D Printable Feedstock Inks for Signal Control or Computation. U.S. Patent Application No. 16/219,188.
Kanarska, Y., et al. 2020. "Numerical Simulations of Conductive Percolating Chiplets Embedded in a Non-Newtonian Polymer Subjected to a Shear Flow." Journal of Non-Newtonian Fluid Mechanics 286. LLNL-JRNL-802729