The research group led by Prof. S. Magdassi, specializing in materials science and nanotechnology. Our primary focus is on the development of inorganic and organic nanomaterials, and their formulation into various inks and delivery systems. These materials find applications in fields such as 3D printing, solar energy, biomedical systems, optics and soft robotics. Our research has led to commercial success with global sales and the establishment of new companies.

3D and 4D printing

The field of additive manufacturing, also known as three-dimensional printing, has undergone significant development in recent years. With this development, there is a growing need for new materials to fabricate functional 3D structures. This technology is currently used for various applications ranging from modelling to medical devices.

At present, the most commonly used methods for 3D printing are based on layer-by-layer fabrication of a three-dimensional structure. There are four methods for building each layer: (1) Fuse Deposition Modelling (FDM), which melts a typically polymer material; (2) Selective Laser Sintering (SLS), which uses laser melting of powder particles; (3) Color Jet Printing (CJP), which jets a binder onto a powder; and (4), stereo lithography (SLA), which selectively cures polymerizable monomers. A common technique for this process is digital light processing (DLP), which uses a digital micromirror device (DMD) to selectively polymerize individual pixels within a thin layer, resulting in small dots (tens of micrometers).

Our research is focused on developing new materials suitable for most types of 3D printing technologies, including conductive inks, ceramic materials and metals, and shape memory polymers. We will describe some of our research activities in the following sections.

3D printed organic-ceramic complex hybrid structures with high silica content

New hybrid sol-gel inks that can undergo condensation and radical polymerization have been developed. This enables the fabrication of complex objects by additive manufacturing technology, resulting in 3D objects with superior properties. These 3D objects have very high silica content and are printed using commercial printers that utilize Digital Light Processing. The printed lightweight objects are characterized by excellent mechanical strength (139 MPa) compared to currently used high-performance polymers. The objects also exhibit very high stability at elevated temperatures (Heat Deflection Temperature >270°C), high transparency (89%) and lack of cracks, with glossiness similar to silica glasses. The new inks enable the additive manufacturing of objects composed of both ceramics and organic materials, thus harnessing the advantages of both worlds of materials. https://doi.org/10.1002/advs.201800061

3D printing process of sol gel based inks with dual polymerization mechanisms of complex hybrid 3D object (scale bar, 1cm).

 

Additive manufacturing of transparent silica glass from solutions

We developed an ink composition for 3D printing of transparent silica objects. The ink is based on combining a sol−gel process with photopolymerization for obtaining dense-fused, silica transparent objects. In contrast to recent studies, which used inks based on dispersed silica particles, the sol−gel ink enables us to achieve fused-silica glass at a low temperature, with controlled density and RIs. In addition, control over the density can be realized at the ink preparation step, by enabling the printing of one silica structure with zones of different RIs by a multilateral, 3D printer. Moreover, the new process and the new approach to ink preparation facilitate the fabrication of other metal oxide structures that contain a variety of functional materials. This opens great possibilities in various applications such as optical devices, as well as complex and miniature reactors, including microfluidic devices. DOI: 10.1021/acsami.8b03766

Scheme of printing process and the obtained transparent silica glass objects at different stages. Printed waveguide and miniature flask filled with colored water.

 

3D printing of responsive hydrogels for drug-delivery systems

We have developed a hydrogel formulation that could function as a model for a 3D-printed, controlled drug delivery system. Hydrogel tablets with complex structures were printed using acrylic acid as the monomer and polyethylene glycol diacrylate (PEGDA) as a cross-linker, resulting in a responsive drug-delivery system.

We have demonstrated using 3D printing to improve the performance of classic solid dosage forms by offering new ways to control drug release as a function of pH and surface area while controlling geometry parameters. We have shown a good correlation between the swelling of the tablets and the release of a model drug, meaning we can tune the drug release by designing specific shapes with the desired surface area. It is expected that advancing this technology will eventually provide an essential means for personalized drug delivery by controlling critical parameters for drug action and absorption. DOI: 10.2217/3dp-2017-0009

Images of the 3D printed hydrogel tablets using digital light processing technique. (A) Box. (B) Hemisphere. (C) 5 × 5. (D) Hive. (E–F) are scanning electron microscopy images of D and C shapes, respectively.

 

Porous structures by printing Oil-in-Water emulsions

A new ink  was developed for printing porous structures that can be used for embedding various functional materials. The ink is composed of a UV polymerizable Oil-in-Water emulsion which can be converted into a solid object upon UV irradiation, forming a porous structure after evaporation of the water phase. The water phase can contain silver NP that are sintered by a chemical sintering, resulting in a 3D conductive structure (Fig.2). The surface area of the object can be controlled by changing the emulsion's droplets size and the dispersed phase fraction. see: Journal of Materials Chemistry C 1.19 (2013): 3244-3249. and Journal of Materials Chemistry C 3.9 (2015): 2040-2044. 

Printed 3D porous (left) and conductive objects (right).

 

3D and 4D printing of shape memory materials

Until now, Shape Memory Polymers  (SMPs) were not used in the field of 3D printing or flexible electronics due to inadequate processing technologies. We developed a new process and inks which enables printing of oligomer melts in a DLP printer, to generate high-resolution three-dimensional (3D) shape memory structures (Fig. 3). We also demonstrated how these printed structures can be further utilized for constructing flexible electronic devices (Fig.4), see:  Adv. Mater.. doi:10.1002/adma.201503132 

3D printed structures changing shape upon heating due to the shape memory polymer.

Printed 3D electrical circuit made of shape memory polymers, activated by heat.

 

Soft robotics

Octopus is one of the primary inspirations for soft robotics design.

Soft robotics is a type of robotics that uses compliant materials to build robots that can mimic the physical properties of biological organisms. These robots are designed to enhance safety when working closely with humans and delicate objects, unlike traditional robots that are made of rigid materials. The flexibility of soft robots enables them to navigate through spaces that rigid robots cannot, making them particularly useful in scenarios such as disaster relief. Soft robots are inspired by nature and exploit their flexibility to move efficiently in complex environments, despite the challenges posed by control.

Highly Stretchable and UV Curable Elastomer for Three Dimensional Printing

We have developed compositions of highly stretchable and UV curable (SUV) elastomers that can be stretched by up to 1100%, which is more than five times the elongation at break of the existing UV curable elastomers and are suitable for UV curing based 3D printing technologies. Using DLP printing with the SUV elastomer compositions enabled the direct creation of complex 3D lattices or hollow structures that exhibit extremely large deformation. For example, we directly printed a soft actuator and a soft robotic gripper which have a complex 3D and hollow structures and can undergo large local deformations (Fig. 1). We also demonstrated a 3D Bucky ball light switch by combining the DLP printing with a silver nanoparticles coating and room temperature sintering process. Overall, the SUV elastomers will significantly enhance the capability of the DLP based 3D printing of fabricating soft and deformable 3D structures and devices including soft actuators and robots, flexible electronics, acoustic metamaterials, and many other applications (The scale bar in the figures in 10 mm). Adv. Mater. DOI: 10.1002/adma.201606000

Demostrations of different 3D printed structures such as soft actuator, gripper, spherical balloon and electronic switches using SUV elastomer

 

Medical

This field of research is focused on preparation of nano and microemulsions, microencapsules, and organic nanoparticles, for application in various fields such as imaging and drug delivery.

Example for a delivery system developed in our lab for biomedical imaging is Near Infrared (NIR) fluorescent nanoparticles and liposomes for detection colorectal tumors and ureter visualization. The nanoparticles are prepared by using only non-covalent attachment processes of molecules which are approved for clinical use, see Journal of biomedical nanotechnology 10.6 (2014): 1041-1048. The formation process is schematically shown below.

schematic presentation of formation of NIR nanoparticles for tumor imaging

NIR detection of colorectal cancer

Another example is nanodroplets of pomegranate seed oil (PSO), for prevention and treatment of neurodegenerative diseases (in collaboration with Prof. R. Gabizon, Hadassha Hospital). PSO contains high concentrations of punicic acid, which is among the strongest natural antioxidants, and  it was found that PSO nanoemulsion significantly delayed disease presentation when administered to asymptomatic TgMHu2ME199K mice and postponed disease aggravation in already sick mice, see: Nanomedicine. (2014) Apr 2. pii: S1549-9634(14) 00133-6. The PSO nanoemulsions are further explored by Granalix.

 

Inkjet Printing

Inkjet technology has revolutionized the printing industry in recent decades by providing a new digital and versatile printing method. The process involves shooting ink droplets through an orifice that forms a pattern when it comes into contact with a substrate. Inkjet technology has so far been most successful in graphic arts, including industrial, wide-format printing on flexible and rigid substrates. However, there is growing interest in using inkjet printing for functional materials. Inkjet printing is versatile and has been applied in various fields such as electronics, displays, solar cells, sensors, and even organ printing.

One of the significant advantages of inkjet printing is that it is a non-contact process, which sets it apart from other printing methods. This method can be applied to almost any substrate by tailoring the ink properties according to the substrate's composition, morphology, and other properties. The volume of the jetted droplets is minimal, typically ranging from picoliters, which allows for high precision and reliability. However, to achieve successful printing, ink formulations must meet specific requirements set by inkjet printing technology. Therefore, ink formulations are usually complex and contain various materials such as wetting and rheological agents, polymeric binders, dispersants, and adhesion promoters, depending on the specific application.

 

 A review on the general subject of inkjet inks is given in the book: "The chemistry of inkjet inks" edited by Prof. Magdassi.

 A major activity in the research group is developing inkjet inks with functional properties, such as conductive inks and transparent electrodes. The  inks contain a variety of materials as the functional components, such as metal nanoparticles and carbon nanotubes, dissolved or dispersed metal precursors, glass particles and nanoemulsions. 

 

Printed electronics 

An illustration of an electronic circuit's printing.

Printed electronics refers to the use of printing technologies for creating electronic circuits and devices on various substrates such as polymeric films and paper, which can be rigid, flexible, or even stretchable. Traditionally, electronic devices have been manufactured using complex and expensive methods such as photolithography, electroless deposition, and vacuum deposition. These methods involve multiple steps such as photopolymerization and etching. 

The market for printed electronics is estimated to exceed $300 billion over the next 20 years, and it requires faster, cheaper, and eco-friendlier manufacturing techniques that can be performed with flexible substrates. Recently, there have been many reports on the use of direct printing technologies to fabricate electronic and optoelectronic devices. The main advantage of these additive manufacturing processes is that they deposit only the required material. Printing technologies such as inkjet, transfer, gravure, screen, and flexo enable rapid and low-cost printing of electrical circuits.

All these additive processes require inks tailored to the various printing methods and final applications. The inks for printing electrical conductors are multi-component systems that contain a conducting material in a liquid vehicle (aqueous or organic) and various additives (such as rheology and surface tension modifiers, humectants, binders, and defoamers) that enable optimal performance of the whole system, including the printing device and the substrate. The conductive material may be dispersed nanomaterial such as silver nanowires and copper nanoparticles or a dissolved material such as an organometallic compound and a conductive polymer. Our research group focused on developing silver, copper, and CNT inks. The silver inks were licensed to Nanodimensions through an agreement with Yissum, the tech transfer company of The Hebrew University.

Thermosolar Coatings

Smart coating through wet chemistry to improve harvest of solar energy.

Our group's research aims to develop solar coatings that harvest solar energy and convert it into heat and electricity. We developed (in collaboration with Prof. D. Mandler) coatings which are already in use by BrightSource in a large thermo-solar power plant, producing electricity for over 100,000 homes in California. Our present focus is on forming selective coatings with high absorption in the solar spectrum, low emission in the IR region, and resistance to high temperature by a wet chemical method. The coatings are composed of three layers: absorber layer, IR reflecting layer, and antireflecting as well as protecting layer. The absorber layer absorbs solar light, the IR reflecting layer inhibits the thermal radiation, and the antireflecting layer increases the absorption and protects both the absorber layer and IR reflecting layer from high temperatures.

Colloid science

Colloid and interface science is an interdisciplinary field that combines the principles of chemistry and physics to study heterogeneous systems. Such systems consist of micelles, which are aggregated amphiphilic molecules dispersed in liquids, droplets of a liquid dispersed in another immiscible liquid such as microemulsions, miniemulsions, and emulsions. Additionally, it includes particles with a size ranging from 1 to 1000 nm that are dispersed in a liquid. Since most colloidal systems are unstable, stabilizing agents like surfactants or polymers are required to provide electrostatic, steric, or electrostatic stabilization by adsorbing at the surface of the dispersed particles.

The science of colloid and interface is applied widely in various fields, such as the chemical industry, nanotechnology, biotechnology, ceramics, and paint and ink formulations.

 

For a real life example on a colloidal system watch our movie: "Tahini Water-in-Oil Emulsion Turns Into Oil-in-Water Emulsion" followed by an explanation.

The research projects of our group are in general in two main fields: (i) nanoemulsion and  microemulsion formulations for applications such as drug delivery, imaging, cosmetics and agriculture and (ii) dispersions of nanoparticles for functional printing and coatings. Theses dispersions are applied as conductive inks for printed electronics (metallic nanoparticles and CNTs for fabrication of 2D and 3D electronic devices), solar absorbers in thermosolar and optical coatings, and organic materials as delivery systems. Several of the research activities will are described in the various sections of this website.

 

Printed Solar Cells

Will be added

 

Industrial outcome

New accordion content

 

 

 

 

 

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