Issue link: https://iconnect007.uberflip.com/i/1522641
36 PCB007 MAGAZINE I JUNE 2024 oen with different raw materials. For exam- ple, a company I worked with had a prod- uct that was developed for high-speed digital applications. But when I talk about controlling resin content and construction, you can get to target Dk and Df values for RF. Right at prod- uct development, we had a set of constructions to reference for RF designs. If you wanted Dk of "X," here's your product. For Dk of "Y," it's the same resin system but a different construc- tion and resin content. at is a perfect exam- ple of the same product being used in high- speed digital and RF. Hybrid constructions are also becoming more common. People build RF and digital into the same board. One of the sell- ing points for the conventional laminate sup- plier that can also supply RF is that if given the choice, users always prefer to buy all the mate- rials in a stack-up from the same company. Shaughnessy: Ed, this has been great. Thank you for your time. ank you. PCB007 For engineers working on soft robotics or wear- able devices, keeping things light is a constant chal- lenge. Elastomers are synthetic polymers that can be manufactured with a range of mechanical prop- erties, from stiff to stretchy, making them a popular material for such applications. "Elastomers are usually cast so that their compo- sition cannot be changed in all three dimensions over short-length scales. To overcome this problem, we developed DNGEs: 3D-printable double network granular elastomers that can vary their mechani- cal properties to an unprecedented degree," says Esther Amstad, head of the Soft Materials Labora- tory in EPFL's School of Engineering. Eva Baur, a PhD student in Amstad's lab, used DNGEs to print a prototype "finger,", complete with rigid 'bones' surrounded by flexible "flesh." The fin- ger was printed to deform in a pre-defined way, demonstrating the technology's potential to manu- facture devices that are sufficiently supple to bend and stretch, while remaining firm enough to manip- ulate objects. The key to the DNGEs' versatility lies in engineer- ing two elastomeric networks. First, elastomer mic- roparticles are produced from oil-in-water emulsion drops. These microparticles are placed in a precur- sor solution, where they absorb elastomer com- pounds and swell up. The swollen microparticles are then used to make a 3D printable ink, which is loaded into a bioprinter to create the desired structure. The precursor is polymerized within the 3D-printed structure, creating a second elastomeric network that rigidifies the entire object. While the composition of the first network deter- mines the structure's stiffness, the second determines its frac- ture toughness, meaning that the two networks can be fine- tuned independently to achieve a combination of stiffness, toughness, and fatigue resis- tance. One exciting potential appli- cation of DNGEs is in devices for motion-guided rehabilita- tion, where the ability to support movement in one direction while restricting it in another could be highly useful. (Source: EPFL) An Ink for 3D-printing Flexible Devices Without Mechanical Joints