March_2022_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | M A R C H 2 0 2 2 5 6 3D PRINTSHOP A micro-butterfly, printed by del Pozo. The width is around 70 micrometers. Courtesy of Eindhoven University of Technology. ‘SMART INK’ ALLOWS FOR REVERSIBLE 4D PRINTING A researcher from Eindhoven Uni- versity of Technology has developed a “smart ink” that is light-sensitive, pav- ing the way for 4D applications. The basis of the ink lies in the use of liquid crystals. Currently, various smart mate- rials are used for 4D printing. As a rule, these are shape-memory polymers or hydrogels. The disadvantage of the former is that the movements are not reversible. While form changes can take place in the air, they are one-time events. Hydrogels offer the opportunity to switch the form back and forth, but then only underwater. “What we didn’t yet have was a more flexible material, capable of reversing its shapeshifting in various environments in response to stimuli. Now, we can adapt liquid crys- tals in multiple ways. We can play with not only the chemical composition, but also the molecular arrangement,” ex- plains Marc del Pozo Puig. Thus, materials can be designed that are responsive to humidity or tem- perature and whose movement can be precisely controlled. And by combining materials with different functionalities, printed objects can be organized to form a communicating system. He describes another application, a minuscule flower that changes color in response to del Pozo’s breath. “The flower, as small as a red blood cell, has been created with a liquid crystal ink. When I breathe on the flower, which is under a microscope, the ambient hu- midity changes. And with it, the color of the flower. A color change like this can be used as a sensor to register form change, a check that a certain move- ment has taken place.” www.tue.nl. CUSTOM MEDICAL DEVICES FIGHT BACTERIA By optimizing the stiffness of ma- terials that also prevent build-up of bac- terial biofilm, University of Nottingham researchers have discovered how to tailor-make artificial body parts and other medical devices. For example, the method could be adapted to create a highly bespoke one-piece prosthetic limb or joint to replace a lost finger or leg that can fit the patient perfectly to improve their comfort and the prosthet- ic’s durability; or to print customized pills containing multiple drugs, known as polypills, optimized to release into the body in a pre-designed therapeu- tic sequence. For this study, the researchers applied a computer algorithm to de- sign and manufacture, pixel by pixel, 3D-printed objects made up of two polymer materials of differing stiff- ness. By optimizing the stiffness in this way, they successfully achieved cus- tom-shaped and sized parts that offer the required flexibility and strength. www.nottingham.ac.uk . A paper published in Materials Today by researchers at Washington State University says that 3D printing is rapidly changing how materials can be developed. The paper is a roadmap for industry and academics to use 3D printing to design new alloys. “With additive manufacturing you can make a structure for your needs on-demand with not only chemistry or composition control, but also with your desired functionalities at limited cost, time, and maintaining a smaller manufacturing footprint,” says Susmita Bose, FASM, a co-author. wsu.edu . BRIEF A bacteria-repelling artificial finger joint with customized strength distribution made with the multi-material 3D print process. Courtesy of University of Nottingham. Researchers have led efforts to use 3D printing for designing alloys. Courtesy of Washington State University.