Machine learning and 3D printing yield steel-strong, foam-light materials

Good news! Steel with the weight of a feather!

"Researchers at the University of Toronto's Faculty of Applied Science & Engineering have used machine learning to design nano-architected materials that have the strength of carbon steel but the lightness of Styrofoam. ..."

From the abstract:

"Nanoarchitected materials are at the frontier of metamaterial design and have set the benchmark for mechanical performance in several contemporary applications.

However, traditional nanoarchitected designs with conventional topologies exhibit poor stress distributions and induce premature nodal failure.

Here, using multi-objective Bayesian optimization and two-photon polymerization, optimized carbon nanolattices with an exceptional specific strength of 2.03 MPa m3 kg−1 at low densities <215 kg m−3 are created. Generative design optimization provides experimental improvements in strength and Young's modulus by as much as 118% and 68%, respectively, at equivalent densities with entirely different lattice failure responses.

Additionally, the reduction of nanolattice strut diameters to 300 nm produces a unique high-strength carbon with a pyrolysis-induced atomic gradient of 94% sp2 aromatic carbon and low oxygen impurities.

Using multi-focus multi-photon polymerization, a millimeter-scalable metamaterial consisting of 18.75 million lattice cells with nanometer dimensions is demonstrated. Combining Bayesian optimized designs and nanoarchitected pyrolyzed carbon, the optimal nanostructures exhibit the strength of carbon steel at the density of Styrofoam offering unparalleled capabilities in light-weighting, fuel reduction, and contemporary design applications."

Machine learning and 3D printing yield steel-strong, foam-light materials

Strong as steel, light as foam: Machine learning and nano-3D printing produce breakthrough high-performance, nano-architected materials (original news release)

Ultrahigh Specific Strength by Bayesian Optimization of Carbon Nanolattices (open access)

Fig. 1 Multi-objective Bayesian optimization for generative design of carbon nanolattices with high compressive stiffness and strength at low density.

Metasurface makes thermal sources emit laser-like light

Amazing stuff!

"... the new metasurface uses a periodic structure with tailored local perturbations to transform ordinary thermal emissions into something more like a laser beam – an achievement heralded as “just the beginning” for thermal radiation control. ...

The final structure was made from silicon and structured as an array of rectangular pillars (for the non-local interactions) interspersed with elliptical pillars (for the asymmetric emission). Using this structure, the team demonstrated coherent directed emission for six different polarizations, at frequencies of their choice. They also used it to send circularly polarized light in arbitrary directions, and to split thermal emissions into orthogonally polarized components travelling in different directions. While this so-called photonic Rashba effect has been demonstrated before in circularly polarized light, the new thermal metasurface produces the same effect for arbitrary polarizations – something not previously thought possible. ..."

"In a groundbreaking advancement, researchers with the CUNY ASRC have experimentally demonstrated that metasurfaces (two-dimensional materials structured at the nanoscale) can precisely control the optical properties of thermal radiation generated within the metasurface itself. ...

Metasurfaces offer a solution for greater utility by controlling electromagnetic waves through meticulously engineered shapes of nanopillars that are arrayed across their surfaces. By varying these structures, researchers can achieve control over light scattering, effectively “shaping” light in customizable ways. ...

While conventional thermal radiation is unpolarized, a significant focus of the research was enabling thermal radiation with circularly polarized light, where the electric field oscillates in a rotating manner. Recent works had shown that opposite circular polarizations (rotating respectively with left-handed and right-handed features) could be split into opposite directions, but there seemed to be a fundamental limit to further control the polarization of emitted light. The team’s new design transcends this limitation, allowing for asymmetric emission of circular polarization towards a single direction, demonstrating full control over thermal emission. ..."

From the abstract:

"Thermal emission from a hot body is inherently challenging to control due to its incoherent nature. Recent advances have shown that patterned surfaces can transform thermal emission into partially coherent beams with tailored directionality and frequency selectivity. Here we experimentally demonstrate polarization-selective, unidirectional and narrowband thermal emission using single-layer metasurfaces. By implementing polarization gradients across the surface, we unveil a generalization of the photonic Rashba effect from circular polarizations to any pair of orthogonal polarizations and apply it to thermal emission. Leveraging pointwise specification of arbitrary elliptical polarization, we implement a thermal geometric phase and leverage it to prove previous theoretical predictions that asymmetric chiral emission is possible without violating reciprocity. This general platform can be extended to other frequency regimes in efforts to compactify metasurface optics technologies without the need for external coherent sources."

Metasurface makes thermal sources emit laser-like light – Physics World

Researchers Demonstrate Metasurfaces That Control Thermal Radiation in Unprecedented Ways (original news release) "The advance shows promise for creating compact, inexpensive, and portable light sources, which are crucial for space-based applications, biological and geological field research, and military operations."

Local control of polarization and geometric phase in thermal metasurfaces (no public access, but article above contains link to PDF)

Thermal emission control: A thermal metasurface is made of a single layer of nanostructured silicon (gray) on top of glass (blue) and a metal mirror. The nanostructured surface is tailored so that it thermally emits circularly polarized light in the desired direction.

A bizarre metafluid packs programmable properties

Amazing stuff!

"... In this case, the metafluid’s small components are air-filled elastomer spheres between 50 and 500 microns wide, which are suspended in silicon oil. These tiny balls will collapse under pressure, and pop back out when that pressure is relieved, and those two different states will change the metafluid’s properties.

So, for example, when in their full circular shape the balls scatter light, making the fluid look opaque. But under pressure, when they collapse into half-moon shapes, they act like tiny lenses, focusing light and making the metafluid transparent. ..."

"... “We are just scratching the surface of what is possible with this new class of fluid,” ... “With this one platform, you could do so many different things in so many different fields.” ...
Metamaterials — artificially engineered materials whose properties are determined by their structure rather than composition — have been widely used in a range of applications for years. ..."

From the abstract:

"The pursuit of materials with enhanced functionality has led to the emergence of metamaterials—artificially engineered materials whose properties are determined by their structure rather than composition. Traditionally, the building blocks of metamaterials are arranged in fixed positions within a lattice structure. However, recent research has revealed the potential of mixing disconnected building blocks in a fluidic medium. Inspired by these recent advances, here we show that by mixing highly deformable spherical capsules into an incompressible fluid, we can realize a ‘metafluid’ with programmable compressibility, optical behaviour and viscosity. First, we experimentally and numerically demonstrate that the buckling of the shells endows the fluid with a highly nonlinear behaviour. Subsequently, we harness this behaviour to develop smart robotic systems, highly tunable logic gates and optical elements with switchable characteristics. Finally, we demonstrate that the collapse of the shells upon buckling leads to a large increase in the suspension viscosity in the laminar regime. As such, the proposed metafluid provides a promising platform for enhancing the functionality of existing fluidic devices by expanding the capabilities of the fluid itself."

Harvard's bizarre "metafluid" packs programmable properties Harvard engineers have created a strange new “metafluid” – a liquid that can be programmed to change properties, like its compressibility, transparency, viscosity and even whether it’s Newtonian or not.

Intelligent liquid Researchers develop metafluid with programmable response (original news release)

Shell buckling for programmable metafluids (no public access)

When pressure is removed from the fluid, the capsules pop back into their spherical shape.

Novel optical metamaterial may make true one-way glass a reality

Is this not something we have been waiting for for centuries? 😊

"After decades of physics-based theorizing, researchers have succeeded in creating a novel optical metamaterial using conventional materials. Its enhanced electromagnetic effect may make true one-way glass a reality and solar panels more efficient. ...

In optical metamaterials, however, atoms are replaced by meta-atoms that can be structurally engineered to possess properties rarely seen in nature, enabling a design that produces unique electromagnetic responses and allows the precise manipulation of light at the nanoscale.

The ability to control and manipulate light at the nanoscale opens up many applications for metamaterials across various fields. Now, researchers ... have created a new optical metamaterial that may make true one-way glass a reality. ..."

"The new metamaterial takes advantage of the nonreciprocal magnetoelectric (NME) effect. The NME effect implies a link between specific properties of the material (its magnetization and polarization) and the different field components of light or other electromagnetic waves. The NME effect is negligible in natural materials, but scientists have been trying to enhance it using metamaterials and metasurfaces because of the technological potential this would unlock. 

‘So far, the NME effect has not led to realistic industrial applications. Most of the proposed approaches would only work for microwaves and not visible light, and they also couldn’t be fabricated with available technology,’ ... The team designed an optical NME metamaterial that can be created with existing technology, using conventional materials and nanofabrication techniques. 

The new material opens up applications that would otherwise need a strong external magnetic field to work – for example, creating truly one-way glass. Glass that’s currently sold as ‘one-way’ is just semi-transparent, letting light through in both directions.  ..."

From the abstract:

"The nonreciprocal magnetoelectric effect, also known as the Tellegen effect, promises a number of groundbreaking phenomena connected to fundamental (e.g., electrodynamics of axion and relativistic matter) and applied physics (e.g., magnetless isolators). We propose a three-dimensional metamaterial with an isotropic and resonant Tellegen response in the visible frequency range. The metamaterial is formed by randomly oriented bi-material nanocylinders in a host medium. Each nanocylinder consists of a ferromagnet in a single-domain magnetic state and a high-permittivity dielectric operating near the magnetic Mie-type resonance. The proposed metamaterial requires no external magnetic bias and operates on the spontaneous magnetization of the nanocylinders. By leveraging the emerging magnetic Weyl semimetals, we further show how a giant bulk effective magnetoelectric effect can be achieved in a proposed metamaterial, exceeding that of natural materials by almost four orders of magnitude."

Novel optical metamaterial may make true one-way glass a reality

A new optical metamaterial makes true one-way glass possible (Aalto University) Researchers have discovered how to make a new optical metamaterial that would underpin a variety of new technologies.

Optical Tellegen metamaterial with spontaneous magnetization (open access)

Fig. 2: Cobalt-based optical Tellegen meta-atom and isotropic Tellegen metamaterial with its effective material parameters.

Nanomaterial wirelessly stimulates and regrows severed nerves and restores motor function

Good news! Amazing stuff!

"... In creating the particles, researchers at Rice University started with two layers of a metallic glass alloy called Metglas and wedged a piezoelectric layer of lead zirconium titanate in between them. Piezoelectric materials generate electricity when they have mechanical forces applied to them. Metglas is a magnetostrictive material, which means it changes its shape when it has a magnetic field applied to it. In this case, the change in shape of the Metglas in the presence of magnetic pulses caused the piezoelectric material inside to generate an electrical signal. Materials that do this are known as magnetoelectric. ...

Next they tested the material in rats and found that it could not only stimulate peripheral nerves in the rodents when they were under anesthesia, but that it could also restore function in a severed sciatic nerve. It also proved to operate about 120 times faster than similar materials that have been previously developed. ..."

"... The material’s qualities and performance could have a profound impact on neurostimulation treatments, making for significantly less invasive procedures, ...  Instead of implanting a neurostimulation device, tiny amounts of the material could simply be injected at the desired site. Moreover, given magnetoelectrics’ range of application in computing, sensing, electronics and other fields, the research provides a framework for advanced materials design that could drive innovation more broadly. ..."

From the abstract:

"Magnetoelectric materials convert magnetic fields into electric fields. These materials are often used in wireless electronic and biomedical applications. For example, magnetoelectrics could enable the remote stimulation of neural tissue, but the optimal resonance frequencies are typically too high to stimulate neural activity. Here we describe a self-rectifying magnetoelectric metamaterial for a precisely timed neural stimulation. This metamaterial relies on nonlinear charge transport across semiconductor layers that allow the material to generate a steady bias voltage in the presence of an alternating magnetic field. We generate arbitrary pulse sequences with time-averaged voltage biases in excess of 2 V. As a result, we can use magnetoelectric nonlinear metamaterials to wirelessly stimulate peripheral nerves to restore a sensory reflex in an anaesthetized rat model and restore signal propagation in a severed nerve with latencies of less than 5 ms. Overall, these results showing the rational design of magnetoelectric metamaterials support applications in advanced biotechnology and electronics."

Nanomaterial stimulates and regrows severed nerves like sci-fi tech

Rice-engineered material can reconnect severed nerves Magnetoelectric material is first of its kind able to directly stimulate neural tissue

Self-rectifying magnetoelectric metamaterials for remote neural stimulation and motor function restoration (no public access)

Fig. 1: MNMs enable wireless neuromodulation using magnetic fields.

Biochip could detect multiple viruses, cancers, or toxins in minutes

Good news!

"... Now, researchers have shown how to conduct thousands of rapid molecular screenings simultaneously, using light to identify target molecules snared on top of an array of tiny silicon blocks. In theory, the tool could be used to spot 160,000 different molecules in a single square centimeter of space. Developed to spot gene fragments from the SARS-CoV-2 virus and other infectious organisms, the technology should also be able to identify protein markers of cancer and small molecules flagging toxic threats in the environment. ...
an optical detection approach that relies on metasurfaces, arrays of tiny silicon boxes—each roughly 500 nanometers high, 600 nanometers long, and 160 nanometers wide—that focus near-infrared light on their top surface. This focusing makes it easy for a simple optical microscope to detect the shift in the wavelength of light coming from each silicon block, which varies depending on what molecules sit on top. ...
So the technique could allow doctors to detect viral infections without first having to amplify the genetic material from a patient ..."

From the abstract:

"Genetic analysis methods are foundational to advancing personalized medicine, accelerating disease diagnostics, and monitoring the health of organisms and ecosystems. Current nucleic acid technologies such as polymerase chain reaction (PCR) and next-generation sequencing (NGS) rely on sample amplification and can suffer from inhibition. Here, we introduce a label-free genetic screening platform based on high quality (high-Q) factor silicon nanoantennas functionalized with nucleic acid fragments. Each high-Q nanoantenna exhibits average resonant quality factors of 2,200 in physiological buffer. We quantitatively detect two gene fragments, SARS-CoV-2 envelope (E) and open reading frame 1b (ORF1b), with high-specificity via DNA hybridization. We also demonstrate femtomolar sensitivity in buffer and nanomolar sensitivity in spiked nasopharyngeal eluates within 5 minutes. Nanoantennas are patterned at densities of 160,000 devices per cm2, enabling future work on highly-multiplexed detection. Combined with advances in complex sample processing, our work provides a foundation for rapid, compact, and amplification-free molecular assays."

Biochip could detect multiple viruses, cancers, or toxins in minutes | Science | AAAS Bumpy silicon array reveals presence of tiny amounts of DNA—and potentially other types of molecules—without first making copies

Rapid genetic screening with high quality factor metasurfaces (open access)

Fig. 1: Design of high-Q sensors.

This new shock-absorbing material protects like a metal but is light like foam

Amazing stuff!

"Scientists at Johns Hopkins University may have invented the perfect material for protective gear. They’ve devised a new material that is strong and sturdy like metal, but is super lightweight like foam. The material performed very well in preliminary tests, which suggests it could be a real game-changer for the automobile and aerospace industries, as well as the military that could use it to fashion lighter body armor and helmets. ..."

From the abstract:

"A unique rate-dependent energy absorption behavior of liquid crystal elastomer (LCE)-based architected materials is reported. The architected materials consist of repeating unit cells of bistable tilted LCE beams sandwiched between stiff supports. The viscoelastic behavior of the LCE causes the energy absorption to increase with strain rate according to a power-law relationship, which can be modulated by changing the degree of mesogen alignment and the loading direction relative to the director. ... For a multilayered structure of unit cells, nonuniform buckling of the different layers produces additional viscoelastic dissipation. This synergistic interaction between viscoelastic dissipation and snap-through buckling causes the energy absorption density to increase with the number of layers. The sequence of cell collapse can be controlled by grading the beam thickness to further promote viscous dissipation and enhance the energy absorption density. It is envisioned that the study can contribute to the development of lightweight extreme energy-absorbing metamaterials."

This new shock-absorbing material protects like a metal but is light like foam

Synergistic Energy Absorption Mechanisms of Architected Liquid Crystal Elastomers (open access)

Moths draped in stealth acoustic cloak evade bat sonar

Amazing stuff!

"Ultrathin sound absorbers offer lightweight solutions from building acoustics to sonar cloaking. The scales on moth wings have evolved to reduce the echo returning to bats, and we investigate their resonant sound-absorber functionality. Resonant absorbers are most efficient at resonance, and laser Doppler vibrometry (LDV) revealed that an individual moth scale’s three resonance modes indeed span the biosonar frequencies of bats.  ...

Here we investigate moth-scale vibrodynamics to understand their role in creating acoustic camouflage against bat echolocation, where scales on wings provide ultrasound absorber functionality."

Moths draped in stealth acoustic cloak evade bat sonar | Research | Chemistry World Moths can hide from the sonar of feeding bats using their acoustically camouflaged wings. Their evolved stealth adaptation is the result of an array of scales attached to their wing membranes that absorb ultrasound frequencies emitted by hunting bats, and are the first acoustic metamaterials found in nature.

Here is the PNAS paper:

Biomechanics of a moth scale at ultrasonic frequencies

Discretely assembled mechanical metamaterials

Amazing stuff! "Assembling modular parts into materials with unique characteristics"

"... The researchers created four different types of these subunits, called voxels (a 3D variation on the pixels of a 2D image). Each voxel type exhibits special properties not found in typical natural materials, and in combination they can be used to make devices that respond to environmental stimuli in predictable ways. Examples might include airplane wings or turbine blades that respond to changes in air pressure or wind speed by changing their overall shape. ..."

Probably, voxel is the wrong term here in my estimation!

"... Mechanical metamaterials offer exotic properties based on local control of cell geometry and their global configuration into structures and mechanisms. ... we present a construction system for mechanical metamaterials based on discrete assembly of a finite set of parts, which can be spatially composed for a range of properties such as rigidity, compliance, chirality, and auxetic behavior. ... This approach benefits from incremental assembly, which eliminates scale limitations, best-practice manufacturing for reliable, low-cost part production, and interchangeability through a consistent assembly process across part types."

Versatile building blocks make structures with surprising mechanical properties | MIT News | Massachusetts Institute of Technology The subunits could be robotically assembled to produce large, complex objects, including cars, robots, or wind turbine blades.

Here is the respective research paper:

Discretely assembled mechanical metamaterials

Israelis invent colorblindness-correcting contact lenses

Good news! Amazing stuff!

"Two Israeli researchers report that they can correct deuteranomaly, a form of red-green colorblindness, with customizable contact lenses.

As reported in the Optical Society journal Optics Letters, Tel Aviv University’s Sharon Karepov and Tal Ellenbogen incorporated ultra-thin optical devices into off-the-shelf contact lenses."
The second researcher has a fascinating name literally translated from German into English: Valley Elbow. I do not remember, I have ever come across a last name of Ellbogen.

Israelis invent colorblindness-correcting contact lenses - ISRAEL21c Their nano-size metasurfaces could be added during the molding stage of contact lens fabrication or thermally fused to a rigid contact lens.

Bayesian Machine Learning in Metamaterial Design

How to make e.g. an umbrella so small that it fits in your pocket?


Credit to Andrew Ng


Bayesian Machine Learning in Metamaterial Design: Fragile Becomes Supercompressible - Bessa - - Advanced Materials - Wiley Online Library: Bayesian machine learning can predict material behavior and quantify the uncertainty of those predictions, even in the presence of manufacturing imperfections. This means that computational data‐driv...