Light-responsive liquid crystalline actuators for microsystems: from molecule to device

Abstract: Liquid crystalline networks represent an interesting class of soft-matter materials, as they can undergo reversible dimensional changes when stimulated. Notably, the direction and magnitude of these dimensional changes can be programmed during the fabrication process. As a result, these materials are suitable for realizing actuating structures whose mechanical response can be tuned.

This work aims to develop fabrication techniques enabling the use of these materials as light-stimulated, flexible materials for actuating microsystem devices. Light is inherently unique as an input stimulus to actuate microsystems due to its ease of control and adaptability in property (wavelength, intensity, polarization) tuning.

To achieve this aim, photoalignment technology is used to orient the liquid crystalline mesogens and thereby program the actuating direction of the actuators. A digital micromirror-based optomechanical setup is used to orient the liquid crystalline mesogens with a spatial resolution of 10µm. Additionally, a maskless photolithography technique is developed, using the same optomechanical setup, to selectively polymerize the mesogens as per the required final shape of the actuator, eliminating the need for additional post-processing steps.

Two different azobenzene photoswitches are employed as a light-actuating mechanism, enabling wavelength-selective actuation triggered by either 365 nm or 450 nm light. Furthermore, the static and dynamic photomechanical performances of various concentrations of liquid crystalline mesogens and azobenzene photoswitches are characterized as a function of different input light intensities. This characterization results in a comprehensive database facilitating the selection of specific mesogens and photoswitches for a particular task. Finally, the developed techniques and methods are combined to demonstrate a light-responsive micro-gripper that can open and close in response to light irradiation.

Overall, this work provides a comprehensive toolbox of methods and techniques, lacking previously, for designing and fabricating liquid crystalline materials as light-responsive actuators for microsystems, whose actuating properties can be tailored to meet the specific demands of a given application

Angaben zum Objekt

• Standort: Deutsche Nationalbibliothek Frankfurt am Main
• Umfang: Online-Ressource
• Sprache: Englisch
• Anmerkungen: Universität Freiburg, Dissertation, 2023

Klassifikation und Themen

• Schlagwort: Flüssigkristall ; Mesogen ; Aktor ; Flüssigkristalline Polymere

Beteiligte, Orts- und Zeitangaben

• Ereignis: Veröffentlichung
• (wo): Freiburg
• (wer): Universität
• (wann): 2024
• Urheber: Lall, Jasleen
• Beteiligte Personen und Organisationen: Zappe, Hans P. ; Albert-Ludwigs-Universität Freiburg. Gisela-und-Erwin-Sick-Professur für Mikrooptik ; Albert-Ludwigs-Universität Freiburg. Fakultät für Angewandte Wissenschaften ; Albert-Ludwigs-Universität Freiburg. Institut für Mikrosystemtechnik

Weitere Informationen

• DOI: 10.6094/UNIFR/243659
• URN: urn:nbn:de:bsz:25-freidok-2436595
• Rechteinformation: Open Access; Der Zugriff auf das Objekt ist unbeschränkt möglich.
• Letzte Aktualisierung: 15.08.2025, 07:21 MESZ