A novel metamaterial inspired resonating structure coupled with a microfluidic channel has been evaluated for sensing applications in the microwave frequency range. The structure is based on an open split ring resonator (OSRR) design, was simulated in a finite element analysis tool (Ansys HFSS R ) and tested using a Vector Network Analyzer to detect changes in resonant frequency, amplitude, and phase due to dielectric loading from different chemicals in the microfluidic channel. The sensor was tested as a single unit cell, in a three cell aperiodic array and as an array of three different frequencies. Different concentrations of water-isopropanol (IPA) and watermethanol were used to characterize the sensor. Additionally, a biosensor application was demonstrated in detecting glucose-d concentration in deionized water. BackgroundThere is a growing demand for inexpensive sensors that can effectively detect changes in material properties in extremely small samples of liquids. Applications range from biomedical devices, lab on chip devices, environmental monitoring and forensic investigations. Optical detection is considered the superior technology for use in microfluidic devices given its predominant use and well understood phenomena [1]. The key technologies from the optical perspective are absorbance detection, fluorescence detection, chemiluminescence detection, interferometric detection, and surface plasmon resonance detection. These approaches can be costly, require regular calibration and are limited in their ability to be miniaturized. Many of these approaches also rely on the use of "tagging", where fluorescent markers are used, which compromise the integrity of the chemical sample. Our approach to use a microstrip based microwave structure does not require calibration, does not require tagging, is simple and inexpensive to fabricate, and can easily be miniaturized.Microfluidic sensors in the microwave and radio frequency region have previously been demonstrated. The work described in [2] had a radio frequency device for sensing changes in small liquid samples that was transmission line based, the work in [3][4][5] use spiral based structures and show good sensitivity in the microwave region as well. Our approach requires a much less complicated design than the proposed system in [2] and has a few key advantages over the spiral based structures. Our structure has its electric field relatively concentrated in key areas on the designs surface meaning our microfluidic channel can be much simpler and smaller, thus requiring less fluid to get results. Our structure is also much smaller than the spiral based designs currently proposed and could be fur-

In this paper, microstrip-based spiral structured artificial magnetic media (metamaterial) coupled with microfluidic channel is experimentally demonstrated for sensing applications. It is found that the resonant frequency and the amplitude changes due to dielectric loading from the introduction of chemical substances in the microfluidic channels. Different concentrations of water -methanol and water -isopropanol samples are used in the characterization of the sensor. For water -methanol mixtures, the resonant frequency shifts from 2.15 GHz to 2.0 GHz with change in dielectric constant from 25 to 75. Results show that the wave propagation in LH-media can be used for interrogation of minute volumes of samples with high sensitivity. IntroductionRapid characterization of chemical and biological samples is increasingly important in clinical, security, safety, drug discovery and industrial applications. Sensing approaches are needed that does not require tagging, (e.g., using fluorescent markers) in order to maintain the samples in their original form while under study. Along with rapid label-free characterization, interrogation of small sample volumes is critically needed in the areas of clinical diagnosis and drug discovery. In this paper, periodic media co-integrated with microfluidic leading to a novel RF near-field sensor is implemented to tackle these challenges. The proposed sensor is simple, cost effective, and can be used for label-free sensing and detection Spiral structured artificial magnetic media (metamaterial) designs have been widely used in the design of compact coplanar waveguides (CPW) and microstrip-based circuit topologies. Recently, split-ring based metamaterial structures that are edge-coupled to a microstrip line have been used in the sensing of biomolecules [1]. In this structure, the interrogation signal (RF) edge couples from a microstrip transmission line to a ring resonator. The biomolecules are made to bind onto the ring resonator. A direct approach of interrogation will be desirable which is more compact and provides improved sensitivity and yet still simple to fabricate and implement. To meet this goal, in this paper, metamaterial structure that is integral part of the microstrip line is employed for sensing application. A spiral based metamaterial transmission was recently introduced, [2 -3], and this design is implemented here for sensing applications.In spiral based metamaterial transmission lines, the periodic arrays of the spiral structure employ left-handed (LH) propagation properties and support backward waves at their fundamental resonance [2]. Motivated by the wave propagation phenomenon of this medium, a microfluidic sensor that interrogates samples in the near-field region is attractive to achieve high sensitivity using low-volumes of samples. This sensor is designed and implemented for

PEEK (poly ether ether ketone) materials printed using FFF 3D printing have been actively studied on applying electronic devices in satellites owing to their excellent light weight and thermal resistance. However, the PEEK FFF process generated cavities inside due to large shrinkage has degraded both mechanical integrity and printing reliability. Here, we have investigated the correlations between nozzle temperatures and PEEK printing behaviors such as the reliability of printed line width and surface roughness. As the temperature increased from 360 to 380 °C, the width of the printed line showed a tendency to decrease. However, the width of PEEK printed lines re-increased from 350 to 426 μm at the nozzle temperatures between 380 and 400 °C, associated with solid to liquid-like phase transition and printed out distorted and disconnected lines. The surface roughness of PEEK objects increased from 49 to 55 μm as the nozzle temperature increased from 380 to 400 °C, where PEEK is melted down and quickly solidified based on more energy and additional heating time at higher printing temperatures at 400 °C. Based on these printing trends, a reliability analysis of the printed line was performed. The printed line formed the most uniform width at 380 °C and had a highest Weibull coefficient of 28.6 using the reliability analysis technique called Weibull modulus.

PEKK (polyether-ketone-ketone) polymer has been actively studied in applying electronic devices in satellites owing to its excellent light weight and thermal resistance. However, the limitation of metal coating to form on the PEKK surface is due to the high-volume resistivity and surface resistance. Here, we have investigated the correlations between the chemical treatment of the surface and adhesion strength between polymer–metal coating. Three-dimensional printed PEKK objects were manufactured and nickel was deposited on the surface by electroless plating. As the concentration of H2SO4 increased from 12.5 to 14.3 mol/L, the pore diameter showed a tendency to increase. However, as growing pore induced connecting each other, the pore size re-decreased from 15.1 to 18.0 mol/L. To control pore size and uniformity, we investigated the pore diameter of 3D printed PEKK as a function of treatment time and temperature. Uniform pores were observed at a temperature of 50 °C which were formed after 10 min and the average pore size was 0.28. After H2SO4 swelling, samples were re-treated in the KMnO4-H3PO4 etching system for the hydrophilic group. KMnO4 broken C=C bonding and generated hydrophilic groups such as -COOH and -OH, the contact angle decreased from 64.7 to 51.1° compared with H2SO4 swelling. XPS survey spectra confirmed that not only breaking C=C bonding but also increasing hydrophilicity due to -OH, -C-, -SO3 and the catalyst absorption of Pd was improved. As a result of adhesive strength by ASTM D3359, compared with the H2SO4 swelling, the KMnO4-H3PO4 etching system showed 5B which is the best result in standard test methods by adhesive tape test and peeling amount on the tape was less than 0.01%.

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