A DIY Fabrication Approach for Ultra-Thin Focus-Tunable Liquid Lens Using Electrohydrodynamic Pump

Demand for variable focus lens is increasing these days due to the rapid development of smart mobile devices and drones. However, conventional mechanical systems for lenses are generally complex, cumbersome, and rigid (e.g., for motors and gears). This research proposes a simple and compact liquid lens controlled by an electro hydro dynamics (EHD) pump. In our study, we propose a do-it-yourself (DIY) method to fabricate the low-cost EHD lens. The EHD lens consists of a polypropylene (PP) sheet for the exterior, a copper sheet for the electrodes, and an acrylic elastomer for the fluidic channel where dielectric fluid and pure water are filled. We controlled the lens magnification by changing the curvature of the liquid interface between the dielectric fluid and pure water. We evaluated the magnification performance of the lens. Moreover, we also established a numerical model to characterize the lens performance. We expect to contribute to the miniaturization of focus-tunable lenses.

Microfluidic Devices with Selectable Optical Pathlength for Quality Control of Alcoholic Solutions

In this work, we present a micro-opto-fluidic platform for the analytical testing of alcoholic solutions (isopropyl alcohol, also known as isopropanol, and ethylene glycol) based on their absorption properties in the wavelength region 1.0–1.7 μm. The investigated fluidic channel is a rectangular glass microcapillary externally coated with aluminum layers, to create a zig-zag guiding effect for the radiation provided by a tungsten lamp. Light crosses the capillary multiple times before being directed towards an optical spectrum analyzer; thanks to the enhanced optical path-length inside the sample, the measurement sensitivity is strongly increased. Preliminary experimental results are reported to show sensing performances.

Damping Characteristics of Fluidic Pressure-fed Mechanism for Positioning Applications

This paper represents a novel approach capable of in-process damping parameter control for nanopositioning systems by implementing a fluidic pressure-fed mechanism (FPFM). The designed internal fluidic channels inside the nanopositioning stage fabricated by a metal additive manufacturing process can be filled with various fluids such as air, water, and oil and pneumatically or hydraulically pressurized. The damping was experimentally characterized with respect to fluids and corresponding pressure level (80 psi) through free-vibration tests, hammering test, and sine input sweeping test in open-loop and closed-loop positioning control conditions. As a result, the FPFM revealed the following characteristics: (1) damping may increase when the internal fluidic channels filled with fluids and pressure level at 80 psi, (2) the dynamic system showed the highest damping when the water exists in internal channels, (3) the existence of fluids and certain pressure in the fluidic channel does not have a significant influence on the motion quality and positioning control, but tracking error was reduced by FPFM. It is expected that the FPFM method will be utilized for vibration and noise control applications for high precision dynamic systems.

Fabrication of microfluidic channel of polydimethylsiloxane using X-ray lithography and its surface nanostructuring

The microfluidic devices have attracted considerable attention for their wide range of applications in healthcare, disease diagnosis, and environmental monitoring. We present the fabrication technique, surface wetting, and bonding of a polydimethylsiloxane (PDMS) microfluidic device that will be used as an electroosmotic micromixerfor biomolecules. This technique essentially requires micromold preparation and casting of PDMS. The hardened mold was fabricated on SU-8 using X-ray lithography (XRL) beamline, BL-7, Indus-2 as the synchrotron radiation source at Raja Ramanna Centre for Advanced Technology(RRCAT). The PDMS casting and thermal cross-linking was performed by spin-coating, followed by heating with specific thermocycle. This cross-linked PDMS was bonded with smooth surfaces that were treated with different reactive plasmas using a deep reactive-ion etching (DRIE) system. In a micro fluidic channel, the flow is usually a highly ordered laminar flow and due to lack of turbulence the mixing is very difficult for larger molecules such as peptides, proteins and high-molecular-weight nucleic acids. Here, we propose a microscale mixing device where active mixers are moved by external forces, such as an applied electric field. The dimensions of the fabricated device were generated through computer simulation using the finite-element based COMSOL Multiphysics 5. 4 software. The hydrophobic nature of PDMS hinders the mobility of biomolecules through the microchannel. In this work, plasma-induced surface wettability of PDMS with application of sulfur hexafluoride (SF6) and oxygen (O2) gas recipes was investigated. As a result, the SF6 plasma–treated microchannels became stable hydrophilic and exhibited an increased adhesion or reduced air-bubble trapping during filling with aqueous solutions.

Microwave resonator array with liquid metal selection for narrow band material sensing

A microwave resonator array is integrated with liquid metal to select an individual resonator response within a resonator array, enabling simple and accurate analysis for dielectric sensing. Galinstan, a liquid metal, acts as a multiplexer by inducing a capacitive load to the nearby resonator, lowering its resonant frequency, and thereby isolating its resonant response from other resonators in the array. The liquid metal could be positioned within a fluidic channel to be above any of the resonators, which tuned the resonant frequency from 3.9 to 3.3 GHz where it can be analyzed individually. The resonators showed a consistent response to liquid metal tuning, with tuning error measured below 30 MHz (5%). The sensor also exhibited stable sensitivity to test materials placed on the selected resonator, with a maximum resonant frequency shift of 300 MHz for a dielectric test material (ε = 10.2) and almost no variation in resonant amplitude. The selected resonant response was only sensitive to materials on the selected resonator, and was unaffected by test materials, even when placed on other resonators. The presented design enabled robust and accurate detection of materials using planar microwave resonators that can be controlled at a user’s convenience, specifically for use in systems where multiple parameters or system settings may need to be individually determined.

A Wireless Passive Conductivity Detector for Fluidic Conductivity Analyzation in Microchannel

Electrical conductivity is one of the main parameters of an electrolyte solution. Fluidic conductivity detection and analyzation is very important in many academic research and industrial applications. In order to avoid the issues of the conventional sensing technique, this study utilizes the wireless passive conductivity detector for fluidic conductivity analyzation in the microchannel. The operation of the proposed structure is designed, simulated and then validated by experiments. The experimental results show that the resonance frequency of the sensor decreases from 64.7 MHz to 58.6 MHz according to the rise of KCl concentration in the fluidic channel from 10 mM to 1 M. The dependence of resonance frequency on the distance between inductors was also implemented and analyzed in this work. The integration of the LC passive sensing technique in microfluidic conductivity detector can be utilized in various academic research, industrial application, especially in biosensor applications.

Glycerol–Water Solution-Assisted Mach–Zehnder Temperature Sensor in Specialty Fiber with Two Cores and One Channel

In this paper, we propose an in-fiber Mach–Zehnder temperature sensor based on a dual-core fiber with an eccentric core and a central core. The latter one is beside a fluidic channel embedded in the fiber. The effective refractive index of the guided mode in the central core could be influenced by the glycerol–water solution filled in the fluidic channel. Thus, the transmitted spectrum of the sensor is shifted as a function of temperature. By monitoring the selected spectral dip shifts, an experimental sensitivity of 2.77 nm/°C is obtained in the range of 25 to 40 °C for a solution length of 15 cm. To further improve the temperature sensitivity, the solution length is increased up to 29.5 cm, and a higher sensitivity of 5.69 nm/°C is achieved in the same temperature range. The experimental results agree well with the theoretical ones. The proposed sensor has good robustness and stability, which makes it promising for applications of high precision temperature monitoring.