Report
Teaser, summary, work performed and final results
Periodic Reporting for period 2 - PHOTOTUNE (Tunable Photonic Structures via Photomechanical Actuation)
Teaser
Light is a powerful tool in remote, reversible control over the properties of materials. Through photochemical switching or photothermal heating, one can photomodulate the color, refractive index, mechanical properties, or macroscopic shape/dimensions of soft polymeric...
Summary
Light is a powerful tool in remote, reversible control over the properties of materials. Through photochemical switching or photothermal heating, one can photomodulate the color, refractive index, mechanical properties, or macroscopic shape/dimensions of soft polymeric materials, the latter known as photomechanics. In PHOTOTUNE, we aim at intertwining photomechanics and photonics, by harnessing light-induced macroscopic shape changes to control the optical properties of functional systems. More precisely, we will develop tunable feedback elements and photomechanically controlled nanostructured surfaces, and use them to devise tunable lasers and optical sensing, respectively. Beyond these specific examples, our general goal is to create a new light-based toolbox not only for tunable optical components and sensing platforms, but outreaching also to various different fields such as biomaterials science and soft robotics.
Work performed
Within the first 30 months of the project period, we have concentrated on the development of different kinds photomechanical materials and new actuation schemes. The results have been published in 11 high-level scientific articles (including 2x Nature Communications, 3x Advanced Materials) and one book chapter. Our works have gained lots of publicity in popular science media (e.g., C&EN, New Scientist, Photonics Media) as well as in general newspapers (e.g., USA Today, Daily Mail, in addition to local newspapers). We have mainly focused on novel actuator schemes, demonstrating light-driven materials that are autonomous [Nat. Commun. 2017, 8, 15546], self-regulating [Adv. Mater. 2017, 29, 1701814], programmable [Nat. Commun. 2018, 9, 4148], and multi-responsive [Adv. Mater. 2018, DOI:10.1002/adma.201805985]. Since 2019, the concepts we have learned will be put into use in photonic applications. Finally, we have demonstrated a new optical humidity sensing scheme [ACS Macro Lett. 2018, 7, 381], based on photoswitchable polymers, which will be developed into a proof of concept device in an ERC PoC project OPTOSENSE, launched in September 2018.
Final results
We have progressed beyond the state of the art in both actuator design and optical sensing. Specifically, I would like to point out three developments:
1. In 2017, we demonstrated the “optical flytrap†– photomechanical actuator that “makes decisions†[Nat. Commun 2017, 8, 15546]. By integrating optical fiber and photomechanical actuator, we were able to devise an autonomous actuator whose light response is based on optical feedback it receives from the environment. Alike Venus flytrap, the device only closes when receiving the feedback (from an object that scatters or reflects light), providing means to distinguish between objects, manipulate them, and release them at will.
2. In 2018, we published our work on synergistic photoactuator, allowing us to program the photomechanical response of polymer sheets [Nat. Commun. 2018, 9, 4148]. We used photochemical actuation for shape programming and photoinduced heating for shape morphing, to obtain light-reconfigurable shape deformations.
3. Our work on photoswitching-based optical humidity sensor presents a new way to measure relative humidity from the environment [ACS Macro Lett. 2018, 7, 381]. The concept is based on integrating photoswitchable molecules into polymer matrices. When properly chosen the photoswitching kinetics of the molecules depends exponentially on environmental humidity, providing an excellent basis for device applications and will be further developed in an ERC Proof of Concept project OPTOSENSE (Agreement No. 789788).
For the next 30 months, more effort will be put into tunable photonics. We expect to demonstrate phototunable lasing and phototunable plasmonic substrates, the work towards these directions being well in progress. At the same time, we expect to further explore the fascinating field of light-driven soft robotics, and also use our materials as a bio-platform to, e.g., photomechanically control cell growth.