Ethylene Glycol Based Ferrofluid for the Fabrication of Magnetically Deformable Liquid Mirrors

Abstract

Stable ferrofluids composed of positively charged magnetic iron oxide nanoparticles coated with 2-[2-(2-methoxyethoxy)ethoxy]acetic acid (MOEEAA) are prepared in ethylene glycol. These new ferrofluids exhibit a magnetic response that is equivalent to that found for corresponding citrate stabilized particles. Unlike the uncoated positively charged particles, nanoparticles coated with MOEEAA and dispersed in ethylene glycol remained stable in the presence of a magnetic field. Infrared spectra indicate that surface grafting occurs through the terminal carboxylate group which is bound to the iron oxide nanoparticles both through bridging and unidentate structures. A surface grafting density of 1.2 molecules/nm 2 is determined from thermogravimetry measurements. Although MOEEAA functionalization increases the stability of nanoparticle suspensions in ethylene glycol, surface charge is also essential for the prevention of particle agglomeration. Importantly, the MOEEAA stabilized ferrofluid is compatible with the deposition of surface films of silver nanoparticles and thus allows for the preparation of magnetically deformable liquid mirrors.

Effective Landau theory of ferronematics

“…Since an analytical expression for the integral in Eq. (20) is not available, it is rewritten as a series in powers of |h|:…”

“…Moreover, they offer a broad range of application prospectives such as in medicine [11][12][13] and technology [14][15][16][17]. However, whereas such ferrofluids, i.e., colloidal suspensions of magnetic particles in isotropic liquids, display fascinating behaviors in the presence of an external magnetic field, actual systems exhibit only zero net magnetization once the external field is switched off, i.e., there is no occurrence of spontaneous symmetry breaking [18][19][20][21].…”

Floating and flying ferrofluid bridges induced by external magnetic fields

“…Due to its magnetism and fluidity, the ferrofluid has been used in many fields. [20][21][22][23][24][25][26][27][28][29] Because the ferrofluid's shape and motion can be modified by the external magnetic field, it should be possible to build up a ferrofluid bridge between the ferrofluid in two containers through applying an external magnetic field to them.…”

Optimization of ferrofluid motion on solid substrate and its application to micro-mirror device

“…6) Several actuators have been proposed to control the liquid using thermal, 7) optical, 8) piezoelectric, 9,10) electrostatic, [11][12][13][14][15][16] dielectrophoretic, 17,18) and magnetic actuations. [21][22][23][24][25][26][27][28] Thermal actuation is simple to implement, but shows a slow response time. In addition, this method has disadvantages caused by thermal effects such as heating and evaporation.…”

“…Electrostatic actuation, including electrowetting, has been studied for liquid displays, and has the merits of accurate control, low power consumption, and rapid transition. The magnetic actuation of a liquid has been widely used in cooling systems, 19) lubricating components, 20) optical switches, 21) optical lens, 22) chemical reactions, 23) optical mirrors, [24][25][26][27] and other applications 28) using a ferrofluid.…”