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We investigated a dielectric transmission line consisting of three dielectric substrate layers for millimeter-wave (mmW) applications. This line is referred to as a narrowed dielectric microstrip line (N-DML). The effective dielectric constant method is used to analyze the propagation characteristics of the N-DML. The result of the analysis of the normalized phase constant is consistent with the simulation. For demonstration, two J -band N-DML prototypes of different lengths with transitions to rectangular waveguides were designed, fabricated, and measured. Good agreement between the simulated and measured results is observed. In particular, due to its nonmetal structure, the N-DML shows a low average attenuation constant of only 0.52 dB/cm over 220-280 GHz in the experiment. Due to its good performance, ease of fabrication, low loss, and low cost, the N-DML is a suitable candidate for various mmW applications.

In this study, we explored the concept of introducing asymmetry to cell shapes by patterned cell culture substrates, and investigated the consequence of this induced asymmetry to cell migration behaviors. Three patterns, named "Squares", "Grating", and "Arcs" were fabricated, representing different levels of rotational asymmetry. Using time-lapse imaging, we systematically compared the motility and directionality of mouse osteoblastic cells MC3T3-E1 cultured on these patterns. Cells were found to move progressively faster on "Arcs" than on "Grating", and cells on "Squares" were the slowest, suggesting that cell motility correlates with the level of rotational asymmetry of the repeating units of the pattern. Among these three patterns, on the "Arcs" pattern, the least symmetrical one, cells not only moved with the highest velocity but also the strongest directional persistence. Although this enhanced motility was not associated with the detected number of focal adhesion sites in the cells, the pattern asymmetry was reflected in the asymmetrical cell spreading. Cells on the "Arcs" pattern consistently displayed larger cytoplasmic protrusion on one side of the cell. This asymmetry in cell shape determined the direction and speed of cell migration. These observations suggest that topographical patterns that enhance the imbalance between the leading and trailing fronts of adherent cells will increase cell speed and control movement directions. Our discovery shows that complex cell behaviors such as the direction of cell movement are influenced by simple geometrical principles, which can be utilized as the design foundation for platforms that guide and sort cultured cells.

In this study, flexible and uniform multiwall carbon nanotube embedded polydimethylsiloxane (PDMS) sheets were prepared using a vacuum filtration and transfer process. The resistance of the sheets and microstructures were investigated for the fabrication of ideal probe-fed and microstrip-fed patch antennas. Simulation results showed that the resonance and gain of an antenna were affected by the conductivity of the patch significantly. The return loss and gain are acceptable when a conductivity of 10 5 S/m is used. The stretchability test indicated that a gold-coated sheet was more stable than a pristine sheet. Its resistance has a change of 0.5% only, with a displacement of 2500 μm. The frequency-tuning capability was demonstrated using an air inflatable microstrip-fed patch antenna. The working frequency can be tuned by 6.5% with a displacement of 1500 μm, which was higher than that of previously reported MEMS bridge and electrostatic force tunable antennas. This is the first time that a frequency tunable antenna fabricated by PDMS/carbon nanotube is reported. The optimization methods for this type of antenna are discussed and some potential applications such as remote wireless pressure sensors are proposed.

A combinatorial approach was used to present primary neurons with a large library of topographical features in the form of micropatterned substrate for high-throughput screening of physical neural-guidance cues that can effectively promote different aspects of neuronal development, including axon and dendritic outgrowth. Notably, the neuronal-guidance capability of specific features was automatically identified using a customized image processing software, thus significantly increasing the screening throughput with minimal subjective bias. Our results indicate that the anisotropic topographies promote axonal and in some cases dendritic extension relative to the isotropic topographies, while dendritic branching showed preference to plain substrates over the microscale features. The results from this work can be readily applied towards engineering novel biomaterials with precise surface topography that can serve as guidance conduits for neuro-regenerative applications. This novel topographical screening strategy combined with the automated processing capability can also be used for high-throughput screening of chemical or genetic regulatory factors in primary neurons.

This paper presents a multilayer dielectric transmission line — the dielectric microstrip line (DML), for the terahertz (THz) applications. This DML is a metal free transmission line eliminating metal loss, which can be a very serious problem at THz. The E⁁ mode is the main mode in the DML for the electromagnetic wave propagation. A DML with standard waveguide operating within 0.220THz–0.325THz is designed, fabricated and measured for demonstration. With TRL calibration method, phase constant and attenuation constant of the DML are obtained.

Antennas that are fabricated by traditional processes are hard to be reconfigured to a curved shape after fabrication. While, foldable and stretchable antennas are attractive for applications now, such as sensors and can be integrated into textiles and clothes for wearable electronics and out-of-plane designs. In this research, we used polydimethylsiloxane, carbon nanotubes, gold and some secondary raw materials to design and fabricate two types of frequency-tunable soft composite antennas for wireless sensing, utilizing vacuum filtration and transfer process. And after fabrication, we characterized the frequency properties for both of them.

In the present study, fast response resistive-type PI/multiwall carbon nanotube (MWNT) composite films were demonstrated. A composite film with a loading of 3 wt% MWNTs (PIC30) possesses a very linear response nature, a linearity correlation (R2) of 0.99157 and a sensitivity of 0.00146/%RH. The response time were less than five seconds and the resistance changed synchronously with different humidities. The recoverable and repeatable resistive responses affirmed the high efficiency of this film for fast humidity detection. A negative temperature effect was found and proper temperature compensation should be considered in the future applications. The surfaces of the films were found as an organized structure with nano-size dimples, which is helpful for absorption of water molecules. The proposed sensing mechanisms are discussed and it related with tunnel effects, doping of MWNTs by water and a barrier effect between MWNTs.

Control of cell migration is important in numerous key biological processes, and is implicated in pathological conditions such as cancer metastasis and inflammatory diseases. Many previous studies indicated that cell migration could be guided by micropatterns fabricated on cell culture surfaces. In this study, we designed a polydimethylsiloxane cell culture substrate with gratings punctuated by corners and ends, and studied its effects on the behavior of MC3T3-E1 osteoblast cells. MC3T3-E1 cells elongated and aligned with the gratings, and the migration paths of the cells appeared to be guided by the grating pattern. Interestingly, more than 88% of the cells cultured on these patterns were observed to reverse their migration directions at least once during the 16 h examination period. Most of the reversal events occurred at the corners and the ends of the pattern, suggesting these localized topographical features induce an abrupt loss in directional persistence. Moreover, the cell speed was observed to increase temporarily right after each directional reversal. Focal adhesion complexes were more well-established in cells on the angular gratings than on flat surfaces, but the formation of filipodia appeared to be imbalanced at the corners and the ends, possibly leading to the loss of directional persistence. This study describes the first engineered cell culture surface that consistently induces changes in the directional persistence of adherent cells. This will provide an experimental model for the study of this phenomenon and a valuable platform to control the cell motility and directionality, which can be used for cell screening and selection.

A versatile capacitive tactile sensor based on transparent flexible materials is developed in a simple and low-cost fabrication process. The sensor shows an excellent sensitivity (S=2.05 N-1), and is highly sensitive to the load as low as about 3 mN. Moreover, it exhibits a prominent resolution. The excellent device performance is attributed to the creative design of polydimethylsiloxane (PDMS) polymer layer, used as the structural material of the sensor, in which each sensing section acting as a sensor unit is a concave square with hemispheric micro-structured PDMS arrays. Meanwhile, other sections without any PDMS arrays serving as perfect natural wall-barriers can make each sensor unit separated effectively.