Abhishek Dey

Mediator free highly sensitive polyaniline–gold hybrid nanocomposite based immunosensor for prostate-specific antigen (PSA) detection

Polyaniline nanowires (PANI) and gold nanoparticle (AuNPs) based hybrid nanocomposite film fabricated onto a Au substrate has been used to fabricate a mediator free immunosensor for the detection of PSA. Microscopic studies reveal uniform distribution of the AuNPs on the PANI backbone resulting in a nanoporous morphology that provides the desired microenvironment for antibody immobilization. The results of electrochemical studies suggest that AuNPs increase the electro-active surface area of PANI and result in high electron transport in a mediator free electrolyte. The AuNP–PANI hybrid nanocomposite also provides a very effective surface for the immobilization of anti-PSA revealing an increase in electron transport that results in improved sensing performance. The electrochemical response of the anti-PSA/AuNP–PANI/Au immunoelectrode as a function of PSA concentration exhibits a linear range of 1 pg mL−1 to 100 ng mL−1, a detection limit of 0.6 pg mL−1 (lower than ELISA), a sensitivity of 1.4 μA M−1 (higher than ELISA) along with a regression coefficient of 98.99%.

Frequency-Agile Bandpass Filters Using Liquid Metal Tunable Broadside Coupled Split Ring Resonators

A fluidic-based approach for designing tunable coupled resonator bandpass filters is presented. These filters employ broadside coupled split ring resonators (BC-SRR) with one of their open loop resonators constructed from liquid metal. The tuning mechanism is based on dynamically moving the liquid metal to reshape the resonator. To demonstrate the concept, a second order Butterworth filter with continuous tuning range from 650 to 870 MHz is designed and experimentally verified by utilizing PTFE tubing filled with liquid metal and Teflon solution. Due to an inductive external coupling mechanism and 180° rotated resonators, the filter exhibits a near constant 5% fractional bandwidth throughout its tuning range with > 10 dB return and <; 3 dB insertion loss. The filter is realized over a 1.27 mm thick Rogers 6010.2LM substrate and has an approximate footprint of 20 × 40 mm2.

Wideband frequency tunable liquid metal monopole antenna

A frequency tunable liquid metal monopole antenna is introduced. The antenna is formed inside a microfluidic channel embedded within Polydimethylsiloxane (PDMS) substrate. The bottom side of the channel is sealed with 25μm thick liquid crystal polymer (LCP) layer in order to interface the antenna with a conventional microstrip feed line using the capacitive coupling mechanism. The physical length of the antenna is dynamically changed by using pumps to accomplish tunability over a wide frequency range. The concept is demonstrated through the design and experimentation of a 2.9:1 tunable monopole antenna that can operate between 1.7GHz and 4.9GHz.

Microfluidically Controlled Frequency-Tunable Monopole Antenna for High-Power Applications

A microfluidically controlled frequency-tunable monopole antenna with high RF power-handling capability is presented. Different than previous work, the frequency tunability of this monopole is achieved by using a movable metallized plate inside a microfluidic channel. The monopole is capacitively coupled to a feeding microstrip line through a 12- μm-thick benzo-cyclobutene (BCB) insulator that is used to seal and bond the polydimethylsiloxane (PDMS)-based microfluidic channel to the feed board substrate (RO4003C). It is shown that the presented reconfigurable monopole implemented with the metallized plate, low-loss BCB insulator, and RO4003C board exhibits 200% more power-handling capability as compared to prior implementation that relied on liquid metal, liquid crystal polymer, and RO5880 substrate. The presented monopole provides continuous tuning in the 1.7-3.5 GHz range with a tuning ratio of ~ 2:1. The RF power handling of the antenna is demonstrated through the agreement between multiphysics simulations and experiments conducted under high RF power excitation. The liquid metal free nature of the antenna and using BCB to bond the PDMS-based microfluidic channels with the printed circuit board substrates offer a new approach for realizing reconfigurable devices with higher efficiency and high power-handling capability.

Microfluidically Reconfigured Wideband Frequency-Tunable Liquid-Metal Monopole Antenna

A microfluidically reconfigured wideband frequency-tunable liquid-metal monopole antenna is presented. The antenna operation relies on continuous moving of the liquid-metal volume over the capacitively coupled microstrip line feed network with a micropump unit. To maximize the capacitive coupling at the feed point, the antenna is realized by bonding microfluidic channel molds prepared in polydimethylsiloxane (PDMS) polymer with 1-mil-thick liquid crystal polymer (LCP) substrate. The concept is demonstrated through the design and experimentation of a 4:1 frequency-tunable monopole antenna that operates from 1.29 to 5.17 GHz. The presented monopole antenna can also be utilized as an element to form wideband frequency-tunable high-gain antenna apertures without necessitating any additional micropump units. This is accomplished by resorting to strategically meandered or interconnected microfluidic channels. This concept is demonstrated through the design and experimentation of a 4 × 1 microfluidically controlled monopole array capable of providing 2:1 frequency tuning range from 2.5 to 5 GHz.

Passive Feed Network Designs for Microfluidic Beam-Scanning Focal Plane Arrays and Their Performance Evaluation

Microfluidic focal plane arrays (MFPAs) have been recently introduced to implement compact high-gain beam-scanning antennas without resorting to active RF devices. This beam-scanning technique relies on a patch antenna element that can be microfluidically repositioned at the focal plane of a microwave lens. The feed network is strategically designed to be passive and accommodate the position variation in the antenna element. This paper, for the first time, considers the design details and performance evaluation of three different passive network layouts that can potentially be utilized to excite MFPAs. Specifically, resonant corporate, resonant straight, and nonresonant straight microstrip line feed networks are introduced and their loss/bandwidth performances are investigated using the transmission line theory. In addition, a method of moments and ray tracing-based hybrid analysis is utilized to demonstrate the impact of the proposed feed networks on the radiation properties of the MFPA in terms of realized gain and side lobe levels (SLLs). It is shown that the resonant and nonresonant straight microstrip line feed networks reduce the SLL by more than 10 dB relative to the resonant corporate feed network utilized in the prior work. The performance improvements are experimentally verified through an eight-element extended hemispherical dielectric lens-based MFPA prototype. Different than the recent work that relied on liquid metal, the antenna element of this MFPA is implemented from a metalized plate by carrying out flow characterizations on various microfluidic channel geometries. This metalized plate approach paves the way for reliable liquid-metal-free microfluidic reconfigurable devices with higher efficiency and power-handling capabilities.

Small microfluidically tunable top loaded monopole

A recently introduced microfluidically reconfigurable frequency tunable monopole antenna is miniaturized by resorting to a selectively metallized plate for implementing capacitive loading. The selectively metallized plate forms the radiating part of the antenna and is enclosed within a microfluidic channel. The monopole is capacitively coupled to the feed line through a thin insulating layer. The frequency tunability of the antenna is achieved by microfluidically moving the metallized plate to change antenna height. The antenna is measured to operate from 1.8GHz to 3.2GHz with a tuning ratio of 1.7:1 with >2.2dB peak gain.

Microfluidically controlled metalized plate based frequency reconfigurable monopole for high power RF applications

A wideband frequency reconfigurable monopole is introduced for high power RF applications by utilizing the microfluidically repositionable metalized plate technique. The frequency reconfiguration is achieved by extruding or retracting the metallized plate that acts as the radiating antenna. The antenna feed is based on enhanced capacitive coupling through the use of a 12μm thick benzo-cyclobutene (BCB) layer when bonding the microfluidic channels with the PCB board. The fabricated antenna is operated with a bi-directional micropump unit and measured to demonstrate continuous frequency tuning from 1.7GHz to 3.4GHz with >1.5dB realized peak gain. Due to its liquid-metal-free nature, the antenna provides a reliable approach for realizing reconfigurable devices with high power handling capability. The presented agreement between the multiphysics simulations and experiments conducted under 10W RF input power condition supports this possibility by registering an 8.1°C increase over the room temperature of 24.6°C.

MM-wave beam scanning focal plane arrays using microfluidic reconfiguration techniques

Summary form only given. Microfluidic based reconfiguration techniques have been recently shown to provide superior advantages in terms of high power handling capability and wideband tuning range. More recently, our group has introduced the concept of microfluidic based focal plane arrays (FPAs) as a low cost implementation of high gain beam scanning mm-wave arrays (A. Gheethan, R. Guldiken, and G. Mumcu, “Microfluidic Enabled Beam Scanning Focal Plane Arrays,” Presented at the IEEE APS/URSI International Conference, Orlando, FL, 2013). Specifically, our recent work has demonstrated this concept through the design and experimental verification of a 30GHz 1D FPA. The FPA was constructed as a microfluidic channel and placed at the focal surface of an 8cm diameter extended hemispherical microwave lens. A small volume (2.5μL) of liquid metal inside the microfluidic channel acted as a patch antenna and provided the beam scanning functionality when physically moved through the use of a bi-directional micropump unit. Most importantly, the feed network of the FPA was strategically designed to be all-passive by making use of half-wavelength microstrip line resonance mechanisms. Consequently, this all-passive feed network alleviated the need for RF switches and resulted significant reduction in implementation complexity and associated cost as compared to a conventional switched FPA. The microfluidic channel of the FPA was molded inside Polydimethylsiloxane (PDMS). To reduce the substrate loss, the PDMS mold was sealed by a 4mil thick liquid crystal polymer (LCP) layer. The microchannel assembly was placed over a 5mil thick RT5880 substrate that was utilized for implementing the microstrip line based feed network. The experimental verifications demonstrated that the FPA exhibited 3.33% |S<;sub>11<;/sub>| <; -10dB bandwidth and scanned the beam over ±300 field of view (FoV) with a maximum realized gain of 24.8dB. The microfluidic based FPAs radiation efficiency was also shown to be better than that of its RF switched implementations. The resonant based feed network of the aforementioned microfluidic FPA has been shown to produce high level of sidelobe and bandwidth reduction. In this paper, we introduce new resonant and non-resonant based feed network layouts that significantly alleviate the issues of sidelobe and bandwidth. Moreover, we demonstrate a new “liquidmetal-free” implementation of the microfluidic FPA by utilizing metalized plates inside the microfluidic channels as the antenna elements. This constitutes a major deviation towards accomplishing non-toxic and more-reliable device implementations. This paper will also demonstrate techniques for extending the concept of 1D microfluidic based FPAs into 2D by using two bi-directional micropump units (i.e. one per major scan direction).

High resolution surface imaging arrays interrogated with microfluidically controlled metalized plates

Microfluidically controlled metalized plates are proposed for the first time as a low-cost interrogation mechanism for high resolution surface imaging arrays. The pixels of the envisioned imaging system are formed as a dense array of sub-wavelength size slot spiral resonators etched at the ground plane of a microwave substrate. The resonance frequencies of these resonators shift based on the dielectric properties of the material sample within their close proximity. Interrogation of the resonance frequency of each resonator is done by utilizing metalized plates as RF shorts between read-out microstrip lines and resonators. The metalized plates can be repositioned within the microfluidic channels by use of a single micropump unit to sequentially interrogate resonance frequencies of all pixels to extract an image. The concept is introduced through simulations and experiments carried over a 1D material sample. An example 2D imaging system is also presented (through computational simulations) for imaging of tumorous excised breast tissue. The proposed technique alleviates the needs for expensive/complex RF switch based interrogation circuitries or bulky/slow mechanical raster scans.