This seminar is hosted by Dr. Mirko Kovac and the Centre of Excellence in Infrastructure Robotics Ecosystems
Single additive enables 3D printing of highly loaded ceramic suspensions
Ozge Akbulut, Sabancı Üniversitesi, Istanbul, Turkey
Dr. Akbulut is a faculty member at Sabanci University since February 2012. She received her B.S. in Materials Science and Engineering at Sabanci University in 2004. Her PhD from Massachusetts Institute of Technology (MIT, 2009) focused on cost-effective fabrication of biomolecular devices and surface science. She continued her studies as a post-doctoral fellow at Harvard University (2009–2011) on developing tools/techniques for resource-limited settings. Dr. Akbulut’s main research interests are controlling the rheology of highly loaded suspensions with applications in cement industry and additive manufacturing, and silicone-based composites. She also founded a company, Surgitate, on tactile surgical training platforms, in 2014; and acts as a materials expert at F+ Ventures.
There is a consensus, both from commercial suppliers and academia, on the need for precise calibration of interparticle forces to design ceramic inks for additive manufacturing. These forces determine the “printability” of the suspensions by exhibiting a direct effect on the rheological response of the system (e.g, shear thinning, fluid-to-gel transition). The current calibration of these forces relies heavily on electrostatic repulsion and achieves the desired levels by changing the pH of the medium, adding salt, and utilizing polyelectrolyte species as dispersants. Other coagulants, binders, defoamers, and organic solvents might also be present in the formulations, most of the time, in considerable amounts. The conspicious lack of systematic studies for the formulation of inks limits the type and nature of the nanoparticles that are to be used in these inks.
To design a single additive that can offer stability and viscosity-control, we utilized a grafted random copolymer by harnessing both electrostatic repulsion and steric hindrance. We systematically change the charge, ionization capacity, and structure of a grafted random copolymer to formulate inks of iron oxide, barium titanate, alumina, and zirconia. This particle-specific design of an additive enables realization of inks that contain more than 80 wt. % particle loading with less than 1,25 wt.% use of a single additive. We work with the industry extensively and the optimization route that I am going to talk about here has the potential to provide insights for the design of other ‘single additives’ and thus, massively expand the limited portfolio and performance of ceramic inks for 3D printing.
If the time permits, I will discuss the design and fabrication of silicone-based, composite tissue and organ models that are to be used as phantoms in surgical trainings. These tactile models provide realistic responses to surgical interventions, and with their affordability and accessibility, offer a viable alternative to overly-priced or non-existing materials for medical education.
Development of sensors for soft material structures
F. Clemens, Empa – Swiss Federal Laboratories for Materials Science and Technology
Dr. Frank Clemens, is Group Leader (Smart Ceramic Processing) in the Laboratory for High Performance Ceramics at Empa, Swiss Federal Laboratories for Materials Science and Technology, Switzerland. His scientific and applied research belongs to thermoplastic processing of powder based sensors, actuators and structural materials. His group focus in national and international projects in this field, he works with physics, chemists, material scientists and engineers together to investigate activation energies on different processing steps. In addition, he develop new strategies for the processing of soft sensor materials and structures. Since 2003 he is lecturer at ETH Zurich (CH) and since 2010 lecturer at ZHAW (CH). He has more than 120 peer-reviewed articles and patents.
Elastomers are well known soft materials for different applications. Elastomers you can often find in our daily life. Traditionally dampers, sealing or tires are commercial products made of elastomers; tubes and implants are typical medical produces. Thermoplastic elastomers (TPEs) are elastomers, which can be shaped by thermoplastic processing like extrusion or injection molding. Often those TPEs are used to improve the “soft-touch-grip” for tools or grip of a ski-sticks. Soft materials can be filled with inorganic materials to “functionalize” those materials. Magnetic particles are used to achieve magnetorheological dampers. The stiffness of such dampers can be controlled with a magnetic field. Electrical conductive fillers can be used to achieve piezoresistive sensors or chemical detectors. Over the last twenty years, electroactive polymer (EAP), based on elastomer capacitors, have been investigated. With this kind of EAPs, synthetic muscles where successfully developed. EAPs cannot only used for actuation, they can also be used as piezoresitive sensors. To achieve those hybrid materials, typically inorganic particles are dispersed in a elastomer matrix material. This lecture will give an overview on some elastomer based smart materials, their principles and the drawback of those developments.
Alternatively, elastomers based functional materials can be achieved by embedding fibers with sensing or actuation properties. This talk will give an overview on the development and evaluation of reliable soft matter sensor fibers. To achieve electrical conductivity, different kind of nano-carbon materials like carbon black, graphene and carbon nanotubes have been investigated over the last years. Quasi-static and dynamic strain measurements have been performed to investigate drift and relaxation behavior of the sensor composites and the results show that matrix and carbon source strongly affects the electrical resistivity behavior of composite materials. Selected piezoresistive composite material was successfully integrated into different demonstrator designs: Into an industrially woven elastic band and into a 3D printed auxetic design structure. Finally, the piezoresistive sensor designs have been tested for health monitoring, natural user interface and exercise monitoring of robots. The soft matter piezoresitive sensors show very promising results for the analysis of the breathing and pulse of a human. A wrist sensor device for drone and robot control has been successfully tested, and the robots can be easily steered by natural human movements.