2022-09-02, Dalcanale, Federico, Caj, Michaela, Schuler, Felix, Ganeshanathan, Kireedan, Suter-Dick, Laura

Passive mixers and droplet generation microfluidic chip modules were designed and manufactured using a commercial SLA 3D-printer. The mixing modules were designed specifically for 3D-printing and evaluated using FEM modeling. The co-flow droplet generator was used for cancer cells encapsulation and drug potency evaluation.

2020-09, de Wild, Michael, Schuler, Felix

Selective laser melting (SLM) was used to manufacture smart programmed structures with customized properties made of biocompatible NiTi shape-memory alloy. A series of helixes was produced with systematically varied SLM process parameters Laser Exposure Time and Laser Power in order to specifically change the thermo-mechanical material properties of the 3D-structures. This innovation opens up the possibility to adjust the NiTi phase transformation temperature during the manufacturing process. This controllable property determines which of the two crystallographic phases martensite or austenite is present at a certain operating temperature and allows the mechanical properties to be adjusted: martensitic devices are soft and pseudo-plastic due to the shape-memory effect, whereas austenitic structures are pseudo-elastic. In a further step, the SLM process parameters were locally varied within 4D-printed twin-helixes. As a result, the phases, respectively the mechanical properties of a single component were adjusted at different locations. The ratio of elastic to plastic deformation and the spring constant of the helix can be locally controlled. This allows, for example, the spatio-temporal programming of 3D-printed surgical instruments or implants that are stimuli-responsive.

2021-11, Lennart, Rubbert, Schuler, Felix, Gayral, Thibault, de Wild, Michael, Renaud, Pierre

Compliant Wren mechanisms (CWM) constitute specific compliant structures of particular interest. Derived from Wren mechanisms, they can exhibit a large variety of motions, from quasi translation to quasi rotation. In this paper, the development of models for the analysis and synthesis of CWM is considered. A kinematic model is introduced first to assess all possible motions when used as an actuator. Then the static model and stress expressions are derived to help their design. These derivations are achieved for two types of geometries, corresponding to the geometries of interest. CWM are filigree structures, whose manufacturing is difficult to consider without additive manufacturing. A specific work on their production using selective laser melting (SLM) is then achieved to ensure the reliability of their production. As a proof of concept, a pneumatically actuated component is then developed and tested. It is composed of two CWM of different geometries. It offers the possibility to obtain translation and rotation using a single pressure input. The developed models are investigated using finite element models and experiments using additively manufactured structures.

2021, Schuler, Felix, Dany, Sebastian, John, Christoph, de Wild, Michael

Abstract:It is well known that the transition temperatures, e.g. the austenite peak temperature Ap, of NiTi Shape Memory Alloys (SMAs) can be adjusted by changing the alloy composition. This topic recently became more interesting due to the possibilities to produce SMA-parts by additive manufacturing, specifically by Selective Laser Melting (SLM). The potential of new designs and smart structures by so-called 4D-printingwith locally adjusted transition temperatures Appotentially opensup new applicationsand novel temperature-responsive medical devices. This work focuses on the SLM manufacturing parameters exposure time ET(scanning speed) and laser power Pand their impact on the transition temperatureApbeyond the commonly used generic process parameter energy density ED. By systematical variation of process-and scan-parameters, the impact of the P, ET, sample orientation and layer heightLHas well as interdependencies between them have been studied. Awide range of transition temperatures Apbetween -20°C and 70°C has been reached from one starting material by varying ET. These findings potentially allow the manufacturing of smart devices with multi-stage deformation processes in a single 4D-printed part