Browsing by Author "Jao, P.F."

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Fabrication of carbon nanofibrous microelectrode array (CNF-MEA) using nanofiber immersion photolithography
(Institute of Electrical and Electronics Engineers Inc., 2014) Jao, P.F.; Franca E.; Fang S.-P.; Yoon J.; Cho K.; David Sr. E.; Kim G.; Wheeler B.; Yoon, Y.K.
Microelectrode arrays (MEAs) are widely used for stimulating and receiving electrical signals between human and machines and for in vitro neural study. This work demonstrates the fabrication process of nanofibrous 3D microelectrodes using immersion lithography. Oil immersion negates the diffraction effects intrinsic in the photopatterning of electrospun nanofibers to give increased aspect ratio microarchitectures. Nanofiber electrode resistivity is characterized and its performance compared to that of carbon thin film. In vitro testing of electrodes are performed using E18 cortical neurons and analyzed for cell density and cell viability. © 2014 IEEE.
Flexible Liquid Crystal Polymer based complementary split ring resonator loaded quarter mode substrate integrated waveguide filters for compact and wearable broadband RF applications
(Institute of Electrical and Electronics Engineers Inc., 2014) Senior D.E.; Rahimi A.; Jao, P.F.; Yoon, Y.K.
In this paper the flexible Liquid Crystal Polymer (LCP) substrate is used to implement broadband wearable/foldable conformal bandpass filters that use compact cavity resonators working under the principle of quarter mode substrate integrated waveguide (QMSIW), which features a 75% size reduction with respect to the conventional substrate integrated waveguide (SIW) counterpart. Further size reduction is realized with the use of a complementary split ring resonator (CSRR) metamaterial unit cell integrated with the QMSIW architecture. The resulting CSRR-loaded QMSIW cavity has its main resonance frequency below the quasi-TE0.5,0,0.5 resonance mode of the original QMSIW cavity due to the evanescent wave amplification phenomenon with CSRR loading. A low temperature surface micromachining process on the LCP and mechanical drilling of via holes are used for fabrication. The realized CSRR-loaded QMSIW cavity features a moderate quality factor (Q) that makes it useful for the design of bandpass filters with much broader fractional bandwidth (FBW) when compared to those using conventional SIW cavities. A 2nd order and a 3rd order surface micromachined Chebyshev BPFs are demonstrated for operation at a center frequency of 25.5 GHz. More than 11% FBW with an in-band return loss of better than 20 dB and an insertion loss of less than 1.5 dB, including transitions, are obtained for both filters. Theoretical analysis of the working principle is explained. Measured results are in good agreement with the 3D full wave structure simulations. © 2014 IEEE.
Study on high throughput nanomanufacturing of photopatternable nanofibers using tube nozzle electrospinning with multi-tubes and multi-nozzles
(Society of Micro and Nano Systems, 2017) Fang, S.P.; Jao, P.F.; Senior, D.E.; Kim, K.T.; Yoon, Y.K.
High throughput nanomanufacturing of photopatternable nanofibers and subsequent photopatterning is reported. For the production of high density nanofibers, the tube nozzle electrospinning (TNE) process has been used, where an array of micronozzles on the sidewall of a plastic tube are used as spinnerets. By increasing the density of nozzles, the electric fields of adjacent nozzles confine the cone of electrospinning and give a higher density of nanofibers. With TNE, higher density nozzles are easily achievable compared to metallic nozzles, e.g. an inter-nozzle distance as small as 0.5 cm and an average semi-vertical repulsion angle of 12.28° for 8-nozzles were achieved. Nanofiber diameter distribution, mass throughput rate, and growth rate of nanofiber stacks in different operating conditions and with different numbers of nozzles, such as 2, 4 and 8 nozzles, and scalability with single and double tube configurations are discussed. Nanofibers made of SU-8, photopatternable epoxy, have been collected to a thickness of over 80 μm in 240 s of electrospinning and the production rate of 0.75 g/h is achieved using the 2 tube 8 nozzle systems, followed by photolithographic micropatterning. TNE is scalable to a large number of nozzles, and offers high throughput production, plug and play capability with standard electrospinning equipment, and little waste of polymer. © 2017, The Author(s).
Wireless passive sensing application using a cavity loaded evanescent mode half mode substrate integrated waveguide resonator
(2011) Senior D.E.; Cheng X.; Jao, P.F.; Kim C.; Kim J.K.; Yoon, Y.K.
In this work, an evanescent mode half mode substrate integrated waveguide (HMSIW) resonator is designed for a wireless passive sensing application at 5 GHz. The wireless pressure sensor has been implemented by placing a small Polydimethylsiloxane (PDMS) cavity, covered with a metal coated membrane, on top of the original resonator or by using a cavity ground plane. When the metal coated membrane is deformed or deflected by an external pressure, it perturbs the electric field of a complementary split ring resonator (CSRR) patterned on top of the HMSIW, producing a shift in the resonance frequency. Because it operates in a microwave frequency spectrum, it offers a high pressure-frequency sensitivity. Resonance frequency as a function of an applied pressure has been presented. Also, a broadband antenna has been integrated to perform wireless interrogation of the sensor. © 2011 IEEE.