Dr. Adrian Ehrenhofer Profile

Dr. Adrian Ehrenhofer

Research Group Leader at TU Dresden

SPIE Involvement:

Author

Area of Expertise:

Modelling and Simulation , Hydrogels , Materials Informatics , Analogy Modelling , Active Materials

Websites:

Company Website

Publications (6)

Proceedings Article | 20 April 2022 Presentation + Paper

Localized actuation of temperature responsive hydrogel-layers with a PCB-based micro-heater array

Simon Binder, Adrian Ehrenhofer, Tanvir Ahmad, Christopher Reiche, Florian Solzbacher, Thomas Wallmersperger

Proceedings Volume 12042, 120420S (2022) https://doi.org/10.1117/12.2612335

KEYWORDS: Actuators, Ultraviolet radiation, Mirrors, Polymers, Data modeling, Printed circuit board testing, Design and modelling, Finite element methods, Smart materials, Fabrication

Read Abstract +

Proceedings Article | 22 March 2021 Presentation + Paper

Window-opener as an example for environment measurement and combined actuation of smart hydrogels

Adrian Ehrenhofer, Martin Elstner, Angelos Filippatos, Maik Gude, Thomas Wallmersperger

Proceedings Volume 11587, 115870I (2021) https://doi.org/10.1117/12.2582672

KEYWORDS: Environmental sensing, Smart materials, Logic, Humidity, Actuators, Sensors

Read Abstract +

Proceedings Article | 26 May 2020 Paper

An automatically rainproofing bike helmet through light-sensitive hydrogel meshes: design, modeling and experiments

Adrian Ehrenhofer, Alice Mieting, Sascha Pfeil, Johannes Mersch, Chokri Cherif, Gerald Gerlach, Thomas Wallmersperger

Proceedings Volume 11375, 113750N (2020) https://doi.org/10.1117/12.2557728

KEYWORDS: Finite element methods, Coating, Polymers, Composites, Modeling and simulation

Read Abstract +

For everyday cycling, one needs to carry rainproof clothing just for the case of unexpected downpours. In the present research, we present a concept for a helmet which is automatically rainproof when the rain starts. When the sun comes out, the helmet is breathable again even before it completely dries up. This functionality is provided by active hydrogel meshes. Hydrogel meshes offer great advantages due to their ability to change the aperture size with swelling and deswelling. In our current work, we present the design and modeling steps for hydrogel-layered active meshes which use (i) swelling and deswelling in hydrated state and (ii) swelling starting from the dry state. The main goal is to close the air openings of a bicycle helmet when rain starts as an automatic rainproofing. This can be achieved through the swelling of the hydrogel pNiPAAM-co-chlorophyllin in the meshes, which leads to closing when hydrated. At the same time, the light-sensitive behavior leads to opening of the apertures under direct sun exposure, i.e. when the sun appears again after the rain. We present the steps of modeling and design using the Normalized Extended Temperature-Expansion-Model (NETEM) to perform simulations in Abaqus. The model is capable of describing both the swelling of the hydrogel under light stimulus and the volume change due to hydration. It is based on the analogy between free swelling and thermal expansion and defined for nonlinear displacements. We also discuss the fabrication process of hydrogel-layered fibers and challenges in their application and simulation. As a proof of concept for hydrogel-layered meshes, we show preliminary experimental results of a poly(acrylamide)/poly(2-acrylamido-2-methyl-1-propanesulfonic acid) (PAAm/PAMPS) hydrogel with semi-interpenetrated network (SIPN) structure and its swelling capacities on a mesh. Starting from the active hydrogel meshes as presented in the current work, the next step can be smart textiles that harness the power of hydrogels: the adaptation to combinations of stimuli – like humidity, temperature and brightness - that define environments.

Proceedings Article | 29 March 2019 Presentation + Paper

Active hydrogel composite membranes for the analysis of cell size distributions

Adrian Ehrenhofer, Thomas Wallmersperger

Proceedings Volume 10968, 1096815 (2019) https://doi.org/10.1117/12.2513199

KEYWORDS: Particles, Microfluidics, Composites, Blood, Analytical research, Polymers, Computer simulations

Read Abstract +

Proceedings Article | 17 April 2017 Paper

Hydrogels for engineering: normalization of swelling due to arbitrary stimulus

Adrian Ehrenhofer, Thomas Wallmersperger

Proceedings Volume 10163, 1016321 (2017) https://doi.org/10.1117/12.2259872

KEYWORDS: Thermal modeling, Finite element methods, Sensors, Smart materials, Computer simulations, Glucose, Databases, Data analysis, Chemical engineering, Actuators, Polymers

Read Abstract +

Proceedings Article | 18 April 2016 Presentation + Paper

Simulation of controllable permeation in PNIPAAm coated membranes

Adrian Ehrenhofer, Thomas Wallmersperger, Andreas Richter

Proceedings Volume 9800, 980016 (2016) https://doi.org/10.1117/12.2219117

KEYWORDS: Microfluidics, Composites, Finite element methods, Particles, Biology, Polymers, Blood, Coating, Temperature metrology, Numerical simulations, Smart materials, Microscopy

Read Abstract +

Membranes separate fluid compartments and can comprise transport structures for selective permeation. In biology, channel proteins are specialized in their atomic structure to allow transport of specific compounds (selectivity). Conformational changes in protein structure allow the control of the permeation abilities by outer stimuli (gating). In polymeric membranes, the selectivity is due to electrostatic or size-exclusion. It can thus be controlled by size variation or electric charges. Controllable permeation can be useful to determine particle-size distributions in continuous flow, e.g. in microfluidics and biomedicine to gain cell diameter profiles in blood. The present approach uses patterned polyethylene terephthalate (PET) membranes with hydrogel surface coating for permeation control by size-exclusion. The thermosensitive hydrogel poly(N-isopropylacrylamide) (PNIPAAm) is structured with a cross-shaped pore geometry. A change in the temperature of the water flow through the membrane leads to a pore shape variation. The temperature dependent behavior of PNIPAAm can be numerically modeled with a temperature expansion model, where the swelling and deswelling is depicted by temperature dependent expansion coefficients. In the present study, the free swelling behavior was implemented to the Finite Element tool ABAQUS for the complex composite structure of the permeation control membrane. Experimental values of the geometry characteristics were derived from microscopy images with the tool Image J and compared to simulation results. Numerical simulations using the derived thermo-mechanical model for different pore geometries (circular, rectangle, cross and triangle) were performed. With this study, we show that the temperature expansion model with values from the free swelling behavior can be used to adequately predict the deformation behavior of the complex membrane system. The predictions can be used to optimize the behavior of the membrane pores and the overall performance of the smart membrane.

Showing 5 of 6 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years