Optimization of functions in human-product systems.

Design of products that closely interact with the human body require extensive integration of geometrical and/or physiological knowledge. In that design process it is common to design and validate firstly a human-product system that fulfills a set of specifications, given in advance. The system to be designed often contains some unknown functions that have to be provided by the designer for optimal performance, comfort and safety of the end product. These unknown functions are regularly pinpointed by the designer based on experience, user insights and testing. The past decades, structural optimization techniques such as topological optimization have found their way to standard CAD applications. A commonly known example is found in structural CAD/CAM, e.g. car design, such as a chassis that can be design for 3D printing by only specifying forces (statics & dynamics), optimized for weight, strength, dynamic load and vibrations. A promising application domain is 3D prints of ortheses or prosthetic connections, where statics are optimized towards geometry of the body; to be extended through current research with soft tissue and dynamics. The specific aim of this application is to initiate a design method to deploy state-of-the-art mathematical optimization algorithms and computational methods in the design of flow systems for medical substances, with the aim to optimize therapeutic, diagnostic and/or user related effectiveness of the envisioned end product, at the level of system design (human-product system). The specific exercise that is conducted for this aim, within the realm of this small project, is determining the rheology of medical substances (fluids) from experiments that can be easily conducted in vitro. Rheology determines flow behavior which is, in turn, crucial for proper functioning at the level of diagnostics, therapeutics and/or usability. For example, shear stresses in cell therapeutics during injection play a crucial role for effectiveness and viability of injected cells at place were they should be active or activated (e.g. under the skin). Shear stresses are also directly related to ease of use for injection, pain and/or discomfort for the subject. Summarizing, shear stress in function of shear rate is the overall determinant for the flow behavior of the substance and in extension the properties of an envisioned applicator. This unknown function (rheology-in Newtonian fluids equivalent with viscosity) will be determined by functional optimization as a generalization of Lagrange multiplicators matched with empirical data. The specific results of this project will enable us to measure rheology with only very limited amount of substance. An additional advantage is that this can be done with easy to handle and achievable equipment, for example a power bench with controlled displacement and respective logged forces. As such, internal shear stresses and flow of medical substances can be modelled easily and accurately, whereas the substance would be otherwise (too) expensive to assess with complex and expensive equipment, normally needed for extensive rheological studies. The acquired info can directly be deployed in the design and optimization of next generation medical applicators, e.g. for intradermal vaccination and/or for therapeutic cell delivery, optimized for therapeutic efficiency and usability. The broader aim of this project is to initiate a method to incorporate state-of-the-art mathematical optimization techniques within the design process of products that require close interaction with the human body. This overall aim will contribute in the long run to the dissemination of powerful mathematical methods for practical applications in product development and industrial design. As such, the project could be a germ for a future proof, data-driven product development process. Insights gained in practical applications and design problems could, in turn, provide input for future math developments.

Keywords:HUMAN-PRODUCT SYSTEM, GENERATIVE DESIGN, OPTIMISATION

Disciplines:Fluid physics and dynamics, Biomedical modelling