Mechanical metamaterials have been designed to achieve custom Poisson’s ratios via the deformation of their microarchitecture. These designs, however, have yet to achieve the capability of exhibiting Poisson’s ratios that alternate by design both temporally and spatially according to deformation. This capability would enable dynamic shape-morphing applications including smart materials that process mechanical information according to multiple time-ordered output signals without requiring active control or power. Herein, both periodic and graded metamaterials are introduced that leverage principles of differential stiffness and self-contact to passively achieve sequential deformations, which manifest as user-specified alternating Poisson’s ratios. An analytical approach is provided with a complementary software tool that enables the design of such materials in two- and three-dimensions. This advance in design capability is due to the fact that the tool computes sequential deformations more than an order of magnitude faster than contemporary finite-element packages. Experiments on macro- and micro-scale designs validate their predicted alternating Poisson’s ratios.
In this work, we demonstrate the high-throughput fabrication of 3D microparticles using a scanning two-photon continuous flow lithography (STP-CFL) technique in which microparticles are shaped by scanning the laser beam at the interface of laminar co-flows. The results demonstrate the ability of STP-CFL to manufacture high-resolution complex geometries of cell carriers that possess distinct regions with different functionalities. A new approach is presented for printing out-of-plane features on the microparticles. The approach eliminates the use of axial scanning stages, which are not favorable since they induce fluctuations in the flowing polymer media and their scanning speed is slower than the speed of galvanometer mirror scanners.
Unconventional computing, such as mechanical1 and microfluidic logic circuits2, quantum gates3, and mechanical metamaterials4 create opportunities for embedded computation, which overcome the power5, package size, and environmental limitations of conventional electronics. Emerging micro-manufacturing capabilities6 with environmentally robust materials enable mechanical logic circuits miniaturization. Kinematically, bistable logic propagates binary signals through cascading gate displacement transitions. Energetically, the inter- and intra- node compliances are tuned for re-programmable signal propagation. Applications need computational architectures which integrate resettable signal propagation7–10, logical operation11–16, and signal storage17–19. While many researchers explore aspects of these elements1, 20–23, none consider energetic limits and propagation dynamics to evaluate and advance the field. Here, we show a generalized model and metrics, validated by experimental results, that enables the design of scale-independent, resettable, mechanical logic circuits. By studying propagation energy flows, we identified non-dimensional operating regimes in which signals propagate and resettable logic is possible. We provide deterministic design methods to evaluate future divergent topologies for displacement-based mechanical logic structures. Our results demonstrate the framework for designing densely integrated mechanical computation systems which harvest available ambient energy to propagate computational cascades. This logic responds to multi-dimensional environmental inputs and thus enables re-programmable, powerless, and embedded computation.
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