Research

Functional nanostructures on unconventional substrates.

Nanofabrication originates in the production of miniaturized electronic circuits, but today is broadly used in various applications, such as miniaturized devices for optics, biomedicine, or energy harvesting. Yet, whereas the traditional nanofabrication processes and equipment are suited exclusively for flat solid substrates, e.g. Silicon wafers, many nowadays and future applications require nano structuring of curved or flexible surfaces, possible only by unconventional, out-of-the-box fabrication approaches.

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In our group, we develop novel approaches for nanoimprint lithography of thermoplastic films on curved substrates, such as lenses. Such a unique nanoimprint process is possible by using an innovative nanocomposite mold structured of an elastomeric substrate with mechanically transferred rigid relief features. Recently, we have demonstrated the application of our nanocomposite molds for thermal nanoimprint of lenses with unprecedented sub-100 nm minimal feature size and resolution.

In addition, we collaborate with RAFAEL Advanced Defense Systems ltd. on the development of novel approaches for antireflective coating on curved optical devices. This collaboration includes two main projects:

  • Direct imprint of biomimetic moth-eye antireflective nanostructures on optical elements made of chalcogenide glasses
  • Nano sphere lithography and pattern transfer by metal deposition, liftoff, and plasma etching of curved substrates

Lithographically directed assembly of 1D nanostructures

1D nanostructures, such as nanowires and nanorods, have been attracting a great deal of interest in the nano-research community as building blocks for functional devices and systems in many applications including electronics, light-emitting, losing and photovoltaics. These nanostructures can be synthesized with a size, shape, and composition that can be controlled at the atomic level.  However, the difficulty in spatially manipulating such miniature objects has constituted a major obstacle towards practical applications. Self-assembly offers an autonomous organization of building blocks at a variety of size scales, however it is driven to reach the lowest energetic state against a decreased entropy, and thus cannot produce arbitrary geometries and long-range order required for functional devices and systems. Therefore, 1D nanostructures cannot be integrated into functional nanosystems by self-assembly alone, but must be guided by a top-down fabricated platform that determines their position.

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In our group, we explore novel approaches for the controlled assembly of 1D nanostructure – nanorods and nanowires – into arbitrary 2D higher architectures, by their chemical docking to nanopatterned functionalities. Recently, we demonstrated controlled assembly of nanodumbells – Au tipped semiconductor nanorods – through their docking to nanoimprinted metallic nanodots functionalized with an organic monolayer, whose terminal thiol groups chemically bind the nanodumbbell tips. This project is done in collaboration with the group of Prof. Taleb Mokari for the Department of Chemistry, BGU. We demonstrated, that the functional nanopattern encodes the nanodumbbell assembly, and can be designed to deterministically position nanodumbbells in two possible modes.  In the single-docking mode, the nanodot arrays are designed with a spacing that exceeds the nanodumbbell length, restricting each nanodumbbell to dock with one edge, and physically connect with its free edge to one of the neighboring nanodumbbells. Alternatively, in the double docking-mode, the nanodots are spaced to exactly fit the nanodumbbell length, allowing nanodumbbell docking with both edges. We found that the docking kinetics can be described by a Random Attachment Model, and verified, that for the used docking chemistry, nanodumbbells that are docked to the same dot do not interact with each other.

Currently, we apply the similar concept for controlled organization of semiconductor nanowires grown from gas phase. Our approach opens a pathway to integration 1D nanostrctures into future nanodevices and nano systems from the bottom up.

Smart multifunctional molecular-scale devices for the spatial control of trnsmebrance receptors in cells

 

Nanodevices with controlled arrays of nanodots functionalized with ligands specific for transmembrane receptors in cells, have been used  for functional analysis of receptor-ligand interactions with precise control of ligand arrangement. Yet, up to date, all the molecular-scale biomimetic nanodevices, those developed by us as well as by other groups, could spatially control only receptors of one certain type. This limitation prevented these devices from being used to study spatiotemporal cross-talks between different receptors. Notably, such cross-talks exist in many biological systems. For instance, cell-cell and cell-matrix adhesion receptors, as well as activating and inhibitory receptors in immune cells, are known to integrate their signaling pathways in various forms. However, the mechanism of such signal integration is barely understood, and could not been investigated up to date on the molecular level due to the lack of an experimental platform that spatially manipulates different receptors at the same time.

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Currently, we develop multifunctional molecular scale biomimetic devices, which simultaneously allow spatial control of individual receptors of different types. To that end, we apply an innovative nanofabrication and surface chemistry to produce nanopatterned arrays of different ligands, and thereby create an artificial extracellular environment that mediate the spatial arrangement of co-stimulating receptors within the cell membrane at the nanometric scale. In addition, we are extensively developing 3D platforms for nano-mimicking cell environment, which are used on the bottom-up approach, such as nanowire. We apply these innovative molecular platforms in three independent research projects, all focused on studying the spatiotemporal signal integration of different receptors:

  • Study of the signal integration between integrins and cadherins in mesenchymal stem cells, and its effect of the cell differentiation, which is done in the collaboration with Jean-Cheng Kuo from Yang-Ming University in Taipei, Taiwan
  • Study of the signal integration between activating and inhibitory receptors in Natural Killer (NK cells), and its effect on NK cell activation and cytotoxic activity, which is done in the collaboration with Angel Porgador  from the department of immunology at the Ben-Gurion University
  • Study of the signal integration between inhibitory and co-stimulating receptors in Chimeric Antigen Receptors (CAR) T cells, and its effect on the formation and activation of CAR immune synapse, which is done in the collaboration with Saba Ghassemi and Michael Milone from the department of Laboratory Medicine and Pathology in UPENN

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