Manufacturing Bits: Jan. 11

3D printing with liquids
Martin Luther University Halle-Wittenberg (MLU) has developed a way to combine both materials and liquids in 3D printing applications.

Researchers from MLU have developed liquid‐filled capsules using 3D printing technology. This in turn enables new medical agents to be incorporated into pharmaceutical products. It also allows liquids to be integrated into materials.

3D printing uses a specialized printer to develop three-dimensional objects from a CAD model. In 3D printing, materials are deposited layer-by-layer to create various products.

This method uses materials, which are liquefied through heat and become solid after printing, according to researchers. “If the finished product is to contain liquid components, these are usually added afterwards,” according to researchers at MLU. “This is time-consuming and costly.”

In response, researchers from MLU combined common 3D printing processes with traditional printing methods like inkjet or laser printers. For this, liquids are added drop by drop at the desired location. This takes place during the extrusion of the basic material.

“Using a two‐print‐head system (fused deposition modeling extruder and a liquid inkjet print head), micro‐sized capsules are manufactured in sizes ranging from 100 to 800µm. The thermoplastic polymer poly(ε‐caprolactone) (PCL) is chosen as matrix/shell material due to its optimal interaction with the embedded hydrophobic liquids. First, the core–shell capsules are printed with model liquids and pure PCL to optimize the printing parameters and to ensure fully enclosed capsules inside the polymer,” said Harald Rupp and Wolfgang Binder from MLU in Advanced Materials, a technology journal.

Tiny loudspeakers
Fraunhofer and RWTH Aachen University have developed miniature loudspeakers using a novel inkjet printing and laser technology.

The loudspeakers, which are the size of a 1-cent piece, are based on piezoelectric microelectromechanical systems or piezo-MEMS technology. A piezo-MEMS device is a small component that uses piezoelectricity to generate motion. Piezoelectricity is an electric charge, which builds up in solid materials.

Based on thin piezoelectric layers, a piezo-MEMS device can be used as an actuator or a sensor. “Either they expand when an electric field is applied or they convert mechanical motion into an electrical voltage,” according to Fraunhofer and RWTH. “Accordingly, they are in demand in communications or medical technology, for example, as sensors or actuators in pumps, valves or loudspeakers.”

Piezo-MEMS are based on lead zirconate titanate (PZT) materials. To make piezo-MEMS devices, the industry uses vacuum and mask-based manufacturing methods. But generally, this method is expensive and time-consuming.

In response, Fraunhofer and RWTH have devised a new method using a combination of inkjet printing and laser technology. Researchers are working on the technology based on a joint project called the “Generative Manufacturing of Efficient Piezo-MEMS for Microactuators (GENERATOR).”

To develop tiny loudspeakers based on this process, researchers first developed a PZT-based special ink. Then, the ink is applied to 200mm silicon wafers. Finally, the wafers undergo a crystallization process. This is conducted by means of a laser radiation process at local temperatures of over 700 °C.

Using this approach, researchers devised a multilayer actuator with a total layer thickness of 2µm to 3µm. The actuator had 20nm to 30nm thin PZT layers.

This actuator offers better performance than conventional products. “The beauty of this manufacturing method is the digitally controllable printing and laser processes, which allow instantaneous design changes of the manufactured layers without additional costs for masks or tools and thus also the production of smaller batch sizes,” said Christian Vedder, head of the Thin Film Processing group at Fraunhofer.

3D printing R&D
The National Institute of Standards and Technology (NIST) has awarded $4 million in grants to help accelerate the adoption of new measurement methods and standards to advance U.S. competitiveness in 3D printing, sometimes called metals-based additive manufacturing.

NIST is addressing the barriers to adoption of additive manufacturing, including surface finish and quality issues, dimensional accuracy, fabrication speed, material properties and computational requirements.

“By addressing important measurement challenges, these projects will improve U.S. manufacturers’ ability to use metals-based additive manufacturing to make high-quality, innovative and complex products at high volume,” said Under Secretary of Commerce for Standards and Technology and NIST Director Walter Copan.