Ido Cooperstein

3D Printing of Shape Memory Polymers for Flexible Electronic Devices

The formation of 3D objects composed of shape memory polymers for flexible electronics is described. Layer-by-layer photopolymerization of methacrylated semicrystalline molten macromonomers by a 3D digital light processing printer enables rapid fabrication of complex objects and imparts shape memory functionality for electrical circuits.

High-performance 3D printing of hydrogels by water-dispersible photoinitiator nanoparticles

Photoinitiator nanoparticles enable rapid 3D printing of hydrogels from waterborne systems using digital light printers. In the absence of water-soluble photoinitiators with high absorbance in the ultraviolet (UV)–visible range, rapid three-dimensional (3D) printing of hydrogels for tissue engineering is challenging. A new approach enabling rapid 3D printing of hydrogels in aqueous solutions is presented on the basis of UV-curable inks containing nanoparticles of highly efficient but water-insoluble photoinitiators. The extinction coefficient of the new water-dispersible nanoparticles of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) is more than 300 times larger than the best and most used commercially available water-soluble photoinitiator. The TPO nanoparticles absorb significantly in the range from 385 to 420 nm, making them suitable for use in commercially available, low-cost, light-emitting diode–based 3D printers using digital light processing. The polymerization rate at this range is very fast and enables 3D printing that otherwise is impossible to perform without adding solvents. The TPO nanoparticles were prepared by rapid conversion of volatile microemulsions into water-dispersible powder, a process that can be used for a variety of photoinitiators. Such water-dispersible photoinitiator nanoparticles open many opportunities to enable rapid 3D printing of structures prepared in aqueous solutions while bringing environmental advantages by using low-energy curing systems and avoiding the need for solvents.

3D printing of porous structures by UV-curable O/W emulsion for fabrication of conductive objects

The growing interest in the field of three-dimensional printing has led to great demand for new materials. In this paper we should like to present a new ink 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 converts into a solid object upon UV irradiation, and upon evaporation of the aqueous phase, forms a porous structure. The 3D objects with their various porosities, were printed by a Digital Light Processing (DLP) printer. The total surface area of the object can be controlled by changing the emulsions droplets size and the dispersed phase fraction. The printed 3D porous structures can be used in a variety of applications, and here we show a composite conductive object, made of silver and cross-linked polymer. After the porous object is formed, the pores are filled by vacuum, dipping in a dispersion of silver nanoparticles, followed by chemical sintering at room temperature, which results in conductive percolation paths within the 3D structure. Application of this structure is demonstrated for use as a 3D connector of an electrical circuit.

UV crosslinkable emulsions with silver nanoparticles for inkjet printing of conductive 3D structures

3D conductors are developed by inkjet printing a UV curable ink composed of oil-in-water emulsion combined with a dispersion of silver nanoparticles. Upon UV radiation by LED light the droplets immediately polymerize and form solid structures with embedded silver nanoparticles. The unique composition of the new ink enables sintering of the silver nanoparticles at room temperature by contact with NaCl solution, leading to a conductivity of 1.9 × 106 S m−1 while maintaining the 3D structure. The aspect ratio for photo-polymerized printed lines is more than 10 times larger than that of non-irradiated lines. The emulsion–dispersion new inks are potential materials for 3D fabrication of conductors and other functional materials in printed electronics.

4D printing shape memory polymers for dynamic jewellery and fashionwear

ABSTRACT 4D printing is a novel approach that enables dynamic functionality in ordinary static object. We used a methacrylated semicrystalline polymer to print objects exhibiting thermally triggered shape memory behaviour. By exploring various molecular weights, it was found that a methacrylated polycaprolactone polymer with a number average molecular weight of 10,000 g mol−1 exhibited the best thermal and mechanical behaviour. The effect of dyes’ addition to the ink formulation on the photopolymerisation and on the printing processes was evaluated. The ink was utilised for demonstrating fabrication of dynamic jewellery and a shoe accessory by Digital Light Processing printing.

Three-dimensional printing of scintillating materials

We demonstrate, for the first time, the applicability of three-dimensional printing techniques to the manufacture of scintillation detectors. We report on the development of a formulation, usable in stereolithographic printing, that exhibits scintillation efficiency on the order of 30% of that of commercial polystyrene based scintillators. We discuss the applicability of these techniques and propose future enhancements that will allow tailoring the printed scintillation detectors to various applications.

3D Printing: 3D Printing of Shape Memory Polymers for Flexible Electronic Devices (Adv. Mater. 22/2016).

On page 4449, D. Cohn, S. Magdassi, and co-workers describe a general and facile method based on 3D printing of methacrylated macromonomers to fabricate shape-memory objects that can be used in flexible and responsive electrical circuits. Such responsive objects can be used in the fabrication of soft robotics, minimal invasive medical devices, sensors, and wearable electronics. The use of 3D printing overcomes the poor processing characteristics of thermosets and enables complex geometries that are not easily accessible by other techniques.

Additive Manufacturing of Transparent Silica Glass from Solutions

A sol, aqueous solution-based ink is presented for fabrication of 3D transparent silica glass objects with complex geometries, by a simple 3D printing process conducted at room temperature. The ink combines a hybrid ceramic precursor that can undergo both the photopolymerization reaction and a sol-gel process, both in the solution form, without any particles. The printing is conducted by localized photopolymerization with the use of a low-cost 3D printer. Following printing, upon aging and densifying, the resulting objects convert from a gel to a xerogel and then to a fused silica. The printed objects, which are composed of fused silica, are transparent and have tunable density and refractive indices.

3D-Printed Organic-Ceramic Complex Hybrid Structures with High Silica Content

Abstract Hybrid organic–inorganic sol gel inks that can undergo both condensation and radical polymerization are developed, enabling fabrication of complex objects by additive manufacturing technology, yielding 3D objects with superior properties. The 3D objects have very high silica content and are printed by digital light processing commercial printers. The printed lightweight objects are characterized by excellent mechanical strength compared to currently used high‐performance polymers (139 MPa), 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 fill the gap in additive manufacturing of objects composed of ceramics only and organic materials only, thus enabling harnessing the advantages of both worlds of materials.