AMOLF Institutional Repository
Not a member yet
1351 research outputs found
Sort by
Controlled pathways and sequential information processing in serially coupled mechanical hysterons
Full text linkThe complex sequential response of frustrated materials results from the interactions between material bits called hysterons. Hence, a central challenge is to understand and control these interactions, so that materials with targeted pathways and functionalities can be realized. Here, we show that hysterons in serial configurations experience geometrically controllable antiferromagnetic-like interactions. We create hysteron-based metamaterials that leverage these interactions to realize targeted pathways, including those that break the return point memory property, characteristic of independent or weakly interacting hysterons. We uncover that the complex response to sequential driving of such strongly interacting hysteron-based materials can be described by finite state machines. We realize information processing operations such as string parsing in materia, and outline a general framework to uncover and characterize the FSMs for a given physical system. Our work provides a general strategy to understand and control hysteron interactions, and opens a broad avenue toward material-based information processing
Spontaneous symmetry breaking in plasmon lattice lasers
No full textSpontaneous symmetry breaking (SSB) is key for our understanding of phase transitions and the spontaneous emergence of order. In this work, we report that, for a two-dimensional (2D) periodic metasurface with gain, SSB occurs in the lasing transition. We study diffractive hexagonal plasmon nanoparticle lattices, where the K-points in momentum space provide two modes that are degenerate in frequency and identically distributed in space. Using femtosecond pulses to energize the gain medium, we simultaneously capture single-shot real-space and Fourier-space images of laser emission.
By combining Fourier and real space, we resolve the two order parameters for which symmetry breaking simultaneously occurs: spatial parity and U(1) (rotational) symmetry breaking, evident respectively as random relative mode amplitude and phase. The methodology reported in this work is generally applicable to 2D plasmonic and dielectric metasurfaces and opens numerous opportunities for the study of SSB and the emergence of spatial coherence in metaphotonics
Cholesterol Changes Interfacial Water Alignment in Model Cell Membranes
Full text linkThe nanoscopic layer of water that directly hydrates biological membranes plays a critical role in maintaining the cell structure, regulating biochemical processes, and managing intermolecular interactions at the membrane interface. Therefore, comprehending the membrane structure, including its hydration, is essential for understanding the chemistry of life. While cholesterol is a fundamental lipid molecule in mammalian cells, influencing both the structure and dynamics of cell membranes, its impact on the structure of interfacial water has remained unknown. We used surface-specific vibrational sum-frequency generation spectroscopy to study the effect of cholesterol on the structure and hydration of monolayers of the lipids 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), and egg sphingomyelin (SM). We found that for the unsaturated lipid DOPC, cholesterol intercalates in the membrane without significantly changing the orientation of the lipid tails and the orientation of the water molecules hydrating the headgroups of DOPC. In contrast, for the saturated lipids DPPC and SM, the addition of cholesterol leads to clearly enhanced packing and ordering of the hydrophobic tails. It is also observed that the orientation of the water hydrating the lipid headgroups is enhanced upon the addition of cholesterol. These results are important because the orientation of interfacial water molecules influences the cell membranes’ dipole potential and the strength and specificity of interactions between cell membranes and peripheral proteins and other biomolecules. The lipid nature-dependent role of cholesterol in altering the arrangement of interfacial water molecules offers a fresh perspective on domain-selective cellular processes, such as protein binding
Nineteenth Century Amorphous Calcium Carbonate
Full text linkThe work of the English anatomist George Rainey is compared with that of the Dutch naturalist Pieter Harting. While the latter is regarded as a pioneer in biomimetic inorganic crystallography for precipitating unusual crystallographic forms that mimic the products of living organisms, the work of Rainey largely has been forgotten. In fact, Rainey first prepared amorphous calcium carbonate, a material that can be molded by organisms to form biogenic crystals. Rainey’s extensive experimentation with amorphous calcareous bodies observed in a variety of organisms was at one time considered a significant and pioneering chapter in inorganic chemical morphogenesis and it should reclaim some of its former assessments. Rainey’s interpretations of crystal form and the effects of gravity on crystal growth mechanisms, however, are historical curiosities that should be left behind, except to the extent that they show how the efforts of an individual may appear diminished by the dynamic process of consensus building in science. Harting also prepared amorphous calcium carbonate, but more than a decade after Rainey. While Rainey was a quiet scholar with steady habits, Harting was a statesman, a champion of the down-trodden (albeit with prejudice), a popular educator, a temperance advocate, and a sci-fi novelist, in addition to being a professor. Harting’s public life may account for his outsized place in our collective memory. Rainey’s synthesis of amorphous calcium carbonate in the presence of gum arabic was repeated in a modern setting. Microspheres were characterized by scanning electron microscopy, established as hollow by X-ray microtomography, and were shown to have the composition of calcium carbonate by energy dispersive X-ray analysis. They were amorphous by powder X-ray diffraction
Feedback cooling a levitated nanoparticle's libration to below 100 phonons
Full text linkMacroscopic rotors are interesting model systems to test quantum theory and for quantum sensing. A promising approach for bringing these systems to the quantum regime is to combine sensitive detection with feedback cooling to reduce the thermal occupation of the mechanics. Here, we implement a backward-scattering scheme to efficiently detect all three libration modes of an optically levitated nanoparticle. We demonstrate parametric feedback cooling of all three libration degrees of freedom to below 16 mK, with one of the modes reaching the temperature of 1.3 mK, corresponding to a mean phonon number of 84. Finally, we characterize the backward-scattering scheme by determining its measurement efficiency to be 0.5%
Ion Migration and Space-Charge Zones in Metal Halide Perovskites Through Short-Circuit Transient Current and Numerical Simulations
Full text linkThe inherent ion migration in metal halide perovskite materials is known to induce deleterious and highly unstable dark currents in X- and γ-ray detectors based on those compounds upon bias application. Dark current slow drift with time is identified as one of the major drawbacks for these devices to satisfy industrial requirements. Because dark current establishes the detectability limit, current evolution, and eventual growth may mask photocurrent signals produced by incoming X-ray photons. Relevant information for detector assessment is ion-related parameters such as ion concentration, ion mobility, and ionic space-charge zones that are eventually built near the outer contacts upon detector biasing. A combined experimental (simple measurement of dark current transients) and 1D numerical simulation method is followed here using single-crystal and microcrystalline millimeter-thick methylammonium-lead bromide that allows extracting ion mobility within the range of µion ≈ 10−7 cm2 V−1 s−1, while ion concentration values approximate Nion ≈ 1015 cm−3, depending on the perovskite crystallinity
High-Speed Imaging of Giant Unilamellar Vesicle Formation in cDICE
Full text linkGiant unilamellar vesicles (GUVs) are widely used as in vitro model membranes in biophysics and as cell-sized containers in synthetic biology. Despite their ubiquitous use, there is no one-size-fits-all method for their production. Numerous methods have been developed to meet the demanding requirements of reproducibility, reliability, and high yield while simultaneously achieving robust encapsulation. Emulsion-based methods are often praised for their apparent simplicity and good yields; hence, methods like continuous droplet interface crossing encapsulation (cDICE), which make use of this principle, have gained popularity. However, the underlying physical principles governing the formation of GUVs in cDICE and related methods remain poorly understood. To this end, we have developed a high-speed microscopy setup that allows us to visualize GUV formation in real time. Our experiments reveal a complex droplet formation process occurring at the capillary orifice, generating >30 μm-sized droplets and only in some cases GUV-sized (∼15 μm) satellite droplets. According to existing theoretical models, the oil–water interface should allow for the crossing of all droplets, but based on our observations and scaling arguments on the fluid dynamics within the system, we find a size-selective crossing of GUV-sized droplets only. The origin of these droplets remains partly unclear; we hypothesize that some small GUVs might be formed from large droplets sitting at the second interface. Finally, we demonstrate that proteins in the inner solution affect GUV formation by increasing the viscosity and altering the lipid adsorption kinetics. These results will not only contribute to a better understanding of GUV formation processes in cDICE but ultimately also aid in the development of more reliable and efficient methods for GUV production
A retrofit sensing strategy for soft fluidic robots
Full text linkSoft robots are intrinsically capable of adapting to different environments by changing their shape in response to interaction forces. However, sensory feedback is still required for higher level decisions. Most sensing technologies integrate separate sensing elements in soft actuators, which presents a considerable challenge for both the fabrication and robustness of soft robots. Here we present a versatile sensing strategy that can be retrofitted to existing soft fluidic devices without the need for design changes. We achieve this by measuring the fluidic input that is required to activate a soft actuator during interaction with the environment, and relating this input to its deformed state. We demonstrate the versatility of our strategy by tactile sensing of the size, shape, surface roughness and stiffness of objects. We furthermore retrofit sensing to a range of existing pneumatic soft actuators and grippers. Finally, we show the robustness of our fluidic sensing strategy in closed-loop control of a soft gripper for sorting, fruit picking and ripeness detection. We conclude that as long as the interaction of the actuator with the environment results in a shape change of the interval volume, soft fluidic actuators require no embedded sensors and design modifications to implement useful sensing
Directing Sequential Self-Organization with Self-Assembled Nanocrystals
Full text linkSequential self-organization can be used to design the hierarchy and complexity of materials beyond what is possible with single-step synthesis. However, such sequential approaches introduce additional challenges in maintaining control over the process. To guide the position and orientation of newly nucleated material, we propose the use of self-assembled nanocrystals (SANCs). We test the potential of SANCs in BaCO3|SiO2 nanocomposites, also termed silica biomorphs, to direct the formation of nascent microscopic crystals. We find that SANCs can direct the location and crystallographic orientation of microcrystals at the nucleation stage, while the material, polymorph, and growth behavior of the crystal can be tuned largely independently. Using ion exchange reactions, we show that structures can be unified into a single material of interest in subsequent steps. This level of control over material position, orientation, and chemical composition allows for the retrosynthetic design of complex hierarchical structures
Strain coupling of a single exciton to a nano-optomechanical resonator
Full text linkWe demonstrate the coupling of a semiconductor quantum dot (QD) to an optomechanical cavity, mediated by the strain of a nano-mechanical mode. The device comprises an optomechanical photonic crystal nanobeam in GaAs with embedded In(Ga)As QDs. The flexural mechanical mode of the device can be optically driven exploiting the large optomechanical coupling rate of the cavity. The vibrations generate a time-modulated strain field that shifts the quantum dot transition energy. We observe that optical driving of the mechanical mode induces a shift in an excitonic line corresponding to an estimated vacuum strain coupling rate of 214 kHz. Our approach represents an important step towards the use of phonons to couple different on-chip quantum systems