Research Project: Characterizing Surface-Supported Microdroplets for Optofluidics Applications
Loading...
Contributors
Funders
ID
EC.00012
Authors
Kiraz, Alper
Faculty Member
Publications
Size stabilization of surface-supported liquid aerosols using tapered optical fiber coupling
(Optical Society of America (OSA), 2013) Jonas, Alexandr; Karadağ, Yasin; Kiraz, Alper; Küçükkara, İbrahim; Department of Physics; Graduate School of Sciences and Engineering; Yes; College of Sciences; GRADUATE SCHOOL OF SCIENCES AND ENGINEERING
We demonstrate long-term size stabilization of surface-supported liquid aerosols of salt-water. Single tapered optical fibers were used to couple the light from independent heating and probe lasers into individual microdroplets that were kept on a superhydrophobic surface in a high-humidity chamber. Size stabilization of microdroplets resulted from competition between resonant absorption of the infrared heating laser by a microdroplet whispering gallery mode and water condensation in the sample chamber. Microdroplet size was continuously monitored using the tunable red probe laser. Thanks to the narrow linewidth of the heating laser, stabilization of the 110 mu m radius of a microdroplet with a precision down to 0.54 nm was achieved for a period of 410 s.
Determination of microdroplet contact angles using electrically driven droplet oscillations
(American Institute of Physics (AIP) Publishing, 2011) Kiraz, Alper; Karadağ, Yasin; Jonáš, Alexandr; Tasaltın, Nevin; Department of Physics; Yes; College of Sciences
Oscillatory deformations of micrometer-sized NaCl-water droplets by an AC electric field are used for contact angle measurements on superhydrophobic surfaces. Contact angles are determined from the dependence of the lowest-order resonant frequency of the electrically driven droplet oscillations on the droplet size. The resonant frequency and size of a droplet are found using whispering gallery mode spectroscopy. Measurements are compared with those performed with direct mechanical driving of the droplets using a piezoelectric transducer, and a good agreement is found. The demonstrated contact angle measurement method can be readily integrated into the planar architecture of microfluidic chips.
Probing microscopic wetting properties of superhydrophobic surfaces by vibrated micrometer-sized droplets
(American Chemical Society (ACS), 2011) Jonas, Alexandr; Kiraz, Alper; Taşaltın, Nevin; Karadağ, Yasin; Kücükkara, İbrahim; Department of Physics; Yes; College of Sciences
We determine contact angles of micrometer-sized NaCl-water droplets on superhydrophobic surfaces by analyzing their lowest-order axisymmetric vibrational resonances driven by vertical oscillations of the surface. Fluorescence spectra of the dye-doped droplets excited by laser light feature whisperinggallery modes (WGMs) whose spectral widths depend on the droplet vibration amplitude, thus enabling precise measurements of the droplet mechanical resonant frequency. Following droplet size determination byWGM mode-matching, we calculate the contact angles from the dependence of the measured mechanical resonant frequency on the droplet size for two surfaces with different superhydrophobicity levels, and find a good correlation with the values measured by direct imaging of millimeter-sized droplets.
Lasing in optically manipulated, dye-doped emulsion microdroplets
(Elsevier, 2012) Jonas, Alexandr; Kiraz, Alper; Aas, M.; Department of Physics; Yes; College of Sciences
We introduce a portable, all-liquid microlaser based on optically pumped dye-doped emulsion microdroplets held in a single beam optical trap. We show high stability of the laser emission spectra during prolonged optical manipulation of the droplets within an immiscible host liquid. We investigate the effects of droplet size and dye concentration on the spectral position of lasing wavelength and show how these parameters can be used for the emission wavelength tuning. We also study shifting of the average lasing wavelength to the blue side of the spectrum due to dye photobleaching. The presented optically manipulated fluidic microlasers are disposable and can be easily combined with microfluidic chip technology. This makes them especially attractive for on-chip applications in chemical and biological analysis and sensing.
