Mechanical integrated circuit materials.

Recent developments in autonomous engineered matter have introduced the ability for intelligent materials to process environmental stimuli and functionally adapt1-4. To formulate a foundation for such an engineered living material paradigm, researchers have introduced sensing5-11 and actuating12-16 functionalities in soft matter. Yet, information processing is the key functional element of autonomous engineered matter that has been recently explored through unconventional techniques with limited computing scalability17-20. Here we uncover a relation between Boolean mathematics and kinematically reconfigurable electrical circuits to realize all combinational logic operations in soft, conductive mechanical materials. We establish an analytical framework that minimizes the canonical functions of combinational logic by the Quine-McCluskey method, and governs the mechanical design of reconfigurable integrated circuit switching networks in soft matter. The resulting mechanical integrated circuit materials perform higher-level arithmetic, number comparison, and decode binary data to visual representations. We exemplify two methods to automate the design on the basis of canonical Boolean functions and individual gate-switching assemblies. We also increase the computational density of the materials by a monolithic layer-by-layer design approach. As the framework established here leverages mathematics and kinematics for system design, the proposed approach of mechanical integrated circuit materials can be realized on any length scale and in a wide variety of physics.

Intelligent electroactive material systems with self-adaptive mechanical memory and sequential logic.

By synthesizing the requisite functionalities of intelligence in an integrated material system, it may become possible to animate otherwise inanimate matter. A significant challenge in this vision is to continually sense, process, and memorize information in a decentralized way. Here, we introduce an approach that enables all such functionalities in a soft mechanical material system. By integrating nonvolatile memory with continuous processing, we develop a sequential logic-based material design framework. Soft, conductive networks interconnect with embedded electroactive actuators to enable self-adaptive behavior that facilitates autonomous toggling and counting. The design principles are scaled in processing complexity and memory capacity to develop a model 8-bit mechanical material that can solve linear algebraic equations based on analog mechanical inputs. The resulting material system operates continually to monitor the current mechanical configuration and to autonomously search for solutions within a desired error. The methods created in this work are a foundation for future synthetic general intelligence that can empower materials to autonomously react to diverse stimuli in their environment.

Optomechanical computing in liquid crystal elastomers.

Embodied decision-making in soft, engineered matter has sparked recent interest towards the development of intelligent materials. Such decision-making capabilities can be realized in soft materials via digital information processing with combinational logic operations. Although previous research has explored soft material actuators and embedded logic in soft materials, achieving a high degree of autonomy in these material systems remains a challenge. Light is an ideal stimulus to trigger information processing in soft materials due to its low thermal effect and remote use. Thus, one approach for developing soft, autonomous materials is to integrate optomechanical computing capabilities in photoresponsive materials. Here, we establish a methodology to embed combinational logic circuitry in a photoresponsive liquid crystal elastomer (LCE) film. These LCEs are designed with embedded switches and integrated circuitry using liquid metal-based conductive traces. The resulting optomechanical computing LCEs can effectively process optical information via light, thermal, and mechanical energy conversion. The methods introduced in this work to fabricate a material capable of optical information processing can facilitate the implementation of a sense of sight in soft robotic systems and other compliant devices.

Directing acoustic energy by flasher-based origami inspired arrays.

Acoustic arrays with fixed spatial positions of transducers are used for wave guiding capabilities in the far field. Recent developments in the field of reconfigurable structures reveal that origami inspired foldable arrays may enhance the near and far field wave guiding functionality by virtue of physical shape change. This research explores reconfigurable acoustic arrays based on the deployable flasher tessellation frame using acoustic transducers at mountain crease nodes. Leveraging an experimentally validated model of the flasher acoustic array, this research reveals that arrays with transducers distributed about a spiral arm exhibit higher-order interference that results in broadside directive beam patterns at lower frequencies than radial arm distributions. The class of flasher arrays also exhibits a switching behavior from broadside directive to omnidirectional by virtue of distinct repositioning of the acoustic transducers in the folding process. The discoveries from this research motivate the use of flasher arrays for potential implementation in underwater applications.

Piecewise assembled acoustic arrays based on reconfigurable tessellated structures.

Physically reconfigurable, tessellated acoustic arrays inspired by origami structures have recently been leveraged to adaptively guide acoustic energy. Yet, the prior work only examined tessellated arrays composed from uniform folding patterns, so that the limited folding-induced shape change prohibits broad acoustic field tailoring. To explore a wider range of opportunities by origami-inspired acoustic arrays, here, piecewise geometries are assembled from multiple folding patterns so that acoustic transducer elements are reconfigured in more intricate ways upon array folding. An analytical model of assembled geometries and resulting acoustic wave radiation from the oscillating facets is formulated. Using the theoretical tool, parametric investigations are undertaken to study the adaptation of acoustic energy transmission caused by folding and modularity of the array assembly. A proof-of-concept specimen is fabricated and experiments are conducted to validate the theoretical model and to investigate the efficacy of the piecewise acoustic array concept. The total findings reveal that the assembly of tessellated acoustic arrays may emulate the wave radiation emitted by ideal acoustic sources of intricate shapes. Moreover, by exploitation of origami folding actions, the shape adaptations of the proposed arrays permit straightforward wave guiding opportunities for diverse application needs.

Strategies to predict radiated sound fields from foldable, Miura-ori-based transducers for acoustic beamfolding.

To bypass challenges of digital signal processing for acoustic beamforming applications, it is desirable to investigate repeatable mechanical approaches that accurately reposition transducers for real-time, simple guiding of acoustic energy. One promising approach is to create arrays configured on origami-inspired tessellated architectures. The low dimensionality, easy implementation, compactness, and use of straightforward folding to guide acoustic energies suggest that tessellated arrays may bypass limitations of conventional digital signal processing for beamforming. On the other hand, the challenge of developing such reconfigurable arrays lies in determining tessellation design and folding extent that direct sound as required. This research assesses the utility of the computationally efficient, approximate solutions to Rayleigh's integral to predict radiated sound fields from tessellated arrays based on Miura-ori fold patterns. Despite altering assumptions upon which the integral is derived, it is found that the salient beam-steering properties and amplitudes are accurately reconstructed by the analytical approach, when compared to boundary element model results. Within the far field angular space accommodated by the formulation assumptions, the analytical approach provides a powerful, time-efficient, and intuitive means to identify tessellated topologies and folding extents that empower desired wave-guiding functionalities, giving fuel to the concept of acoustic beamfolding.

Tailoring broadband acoustic energy suppression characteristics of double porosity metamaterials with compression constraints and mass inclusions.

A metamaterial that capitalizes on a double porosity architecture is introduced for controlling broadband acoustic energy suppression properties. When the metamaterial is subjected to static compressive stress, a global rotation of the internal metamaterial architecture is induced that softens the effective stiffness and results in a considerable means to tailor wave transmission and absorption properties. The influences of mass inclusions and compression constraints are examined by computational and experimental efforts. The results indicate that the mass inclusions and applied constraints can significantly impact the absorption and transmission properties of double porosity metamaterials, while the appropriate utilization of the underlying poroelastic media can further magnify these parametric influences. Based on the widespread implementation of compressed poroelastic media in applications, the results of this research uncover how internal metamaterial architecture and constraints may be exploited to enhance engineering noise control properties while using less poroelastic material mass.

Theoretical investigations of energy harvesting efficiency from structural vibrations using piezoelectric and electromagnetic oscillators.

Conversion of ambient vibrational energy into electric power has been the impetus of much modern research. The traditional analysis has focused on absolute electrical power output from the harvesting devices and efficiency defined as the convertibility of an infinite resource of vibration excitation into power. This perspective has limited extensibility when applying resonant harvesters to host resonant structures when the inertial influence of the harvester is more significant. Instead, this work pursues a fundamental understanding of the coupled dynamics of a main mass-spring-damper system to which an electromagnetic or piezoelectric mass-spring-damper is attached. The governing equations are derived, a metric of efficiency is presented, and analysis is undertaken. It is found that electromagnetic energy harvesting efficiency and maximum power output is limited by the strength of the coupling such that no split system resonances are induced for a given mass ratio. For piezoelectric harvesters, only the coupling strength and certain design requirements dictate maximum power and efficiency achievable. Since the harvesting circuitry must "follow" the split resonances as the piezoelectric harvesters become more massive, the optimum design of piezoelectric harvesters appears to be more involved than for electromagnetic devices.

Digital logic gates in soft, conductive mechanical metamaterials.

Integrated circuits utilize networked logic gates to compute Boolean logic operations that are the foundation of modern computation and electronics. With the emergence of flexible electronic materials and devices, an opportunity exists to formulate digital logic from compliant, conductive materials. Here, we introduce a general method of leveraging cellular, mechanical metamaterials composed of conductive polymers to realize all digital logic gates and gate assemblies. We establish a method for applying conductive polymer networks to metamaterial constituents and correlate mechanical buckling modes with network connectivity. With this foundation, each of the conventional logic gates is realized in an equivalent mechanical metamaterial, leading to soft, conductive matter that thinks about applied mechanical stress. These findings may advance the growing fields of soft robotics and smart mechanical matter, and may be leveraged across length scales and physics.

Foundations for Soft, Smart Matter by Active Mechanical Metamaterials.

Emerging interest to synthesize active, engineered matter suggests a future where smart material systems and structures operate autonomously around people, serving diverse roles in engineering, medical, and scientific applications. Similar to biological organisms, a realization of active, engineered matter necessitates functionality culminating from a combination of sensory and control mechanisms in a versatile material frame. Recently, metamaterial platforms with integrated sensing and control have been exploited, so that outstanding non-natural material behaviors are empowered by synergistic microstructures and controlled by smart materials and systems. This emerging body of science around active mechanical metamaterials offers a first glimpse at future foundations for autonomous engineered systems referred to here as soft, smart matter. Using natural inspirations, synergy across disciplines, and exploiting multiple length scales as well as multiple physics, researchers are devising compelling exemplars of actively controlled metamaterials, inspiring concepts for autonomous engineered matter. While scientific breakthroughs multiply in these fields, future technical challenges remain to be overcome to fulfill the vision of soft, smart matter. This Review surveys the intrinsically multidisciplinary body of science targeted to realize soft, smart matter via innovations in active mechanical metamaterials and proposes ongoing research targets that may deliver the promise of autonomous, engineered matter to full fruition.

Deployable tessellated transducer array for ultrasound focusing and bio-heat generation in a multilayer environment.

High intensity focused ultrasound (HIFU) has great potential to thermally ablate diseased tissues with minimal invasion. Yet, HIFU practice has limited cancer treatment potential since the absorption, diffusion, and reflection of ultrasound prevent HIFU from penetrating the body to deep and concealed diseased tissue. To explore a vision of deployable HIFU transducers, this research introduces an origami-inspired concept wherein a deployable tessellated acoustic array is employed to reduce the distance between the HIFU transducer and diseased tissues. A flat-foldable HIFU transducer array is considered, such that the compact shape is used to pass through the human body and then deployed into the operational form for treatment. Here a theoretical framework is developed to study the focusing and thermal heating capabilities of the tessellated array in a multilayer environment. It is observed that the wavefield and thermal elevation realized by the foldable array are functionally similar to those of an ideal arc-shaped transducer. Folding patterns that permit adequate curvature and high quality factor, and that balance slenderness and conformability are found to be beneficial for an ultrasound focusing practice. The efficacy of the analytical predictions are verified through direct numerical simulations. All together, the results encourage attention to foldable array concepts as potential means to advance in-vivo HIFU-based procedures.