Cellulose‐Based Microparticles for Magnetically Controlled Optical Modulation and Sensing. Issue 1 (5th December 2019)

• Record Type: Journal Article
• Authors: Hausmann, Michael K.; Hauser, Alina; Siqueira, Gilberto; Libanori, Rafael; Vehusheia, Signe Lin; Schuerle, Simone; Zimmermann, Tanja; Studart, André R.
• Is Part Of: Small. Volume 16:Issue 1(2020)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2019-12-05
• Subjects: cellulose nanocrystals -- magneto‐optical properties -- microfluidics -- microparticles -- polarized light; Nanotechnology -- Periodicals; Nanoparticles -- Periodicals; Microtechnology -- Periodicals; 620.5
• DOI: 10.1002/smll.201904251
• Languages: English
• ISSNs: 1613-6810

Abstract

Abstract: Responsive materials with birefringent optical properties have been exploited for the manipulation of light in several modern electronic devices. While electrical fields are often utilized to achieve optical modulation, magnetic stimuli may offer an enticing complementary approach for controlling and manipulating light remotely. Here, the synthesis and characterization of magnetically responsive birefringent microparticles with unusual magneto‐optical properties are reported. These functional microparticles are prepared via a microfluidic emulsification process, in which water‐based droplets are generated in a flow‐focusing device and stretched into anisotropic shapes before conversion into particles via photopolymerization. Birefringence properties are achieved by aligning cellulose nanocrystals within the microparticles during droplet stretching, whereas magnetic responsiveness results from the addition of superparamagnetic nanoparticles to the initial droplet template. When suspended in a fluid, the microparticles can be controllably manipulated via an external magnetic field to result in unique magneto‐optical coupling effects. Using a remotely actuated magnetic field coupled to a polarized optical microscope, these microparticles can be employed to convert magnetic into optical signals or to estimate the viscosity of the suspending fluid through magnetically driven microrheology. Abstract : Cellulose‐laden microparticles that enable light manipulation using an external magnetic field are generated in a microfluidic platform. Such a magneto‐optical coupling effect is achieved by combining superparamagnetic nanoparticles and oriented birefringent cellulose nanocrystals within the anisotropic microparticles. When suspended in a liquid medium, these functional microparticles can be exploited to locally probe the viscosity of fluids or to create color‐changing materials.