柯达

Printed Flexible Hybrid Electronics (FHE) can reduce circuit manufacturing costs, but scaling to higher production volumes requires that Roll-to-Roll (R2R) processing replace panel or sheet-to-sheet fabrication methods. Printed silver (Ag) conductors are the most common but are expensive, and often require elevated curing temperatures to raise Ag conductivity, limiting substrate choices. Here we evaluated R2R electroless-plated (EP) copper (Cu) circuits as a lower-cost high-performance metallurgy for FHE due to its high conductivity and compatibility with lower-cost, lower thermal-stability substrates.Eastman Kodak’s high-resolution R2R flexographic printing process first prints a thin catalytic circuit pattern on a substrate web. This is followed by electroless Cu build-up on the catalyst pattern. This process can produce EP Cu traces down to ~20 μm in width. Because device electrical, mechanical, and environmental performance depends on the combination of materials, process, and design, Cu conductors are designed as semi-solid meshes with opening sizes and plated thickness is adjusted to optimize transparency, conductivity, and Cu fatigue life.Test-vehicle (TV) coupons with Surface Mount Technology (SMT) pads and bend/flex test structures containing three mesh designs (with varying Cu coverages) were fabricated on a continuous-web of Polyethylene terephthalate (PET). The narrowest EP Cu traces were ~20 μm wide and ~1.5 μm thick with internal interconnecting-mesh linewidths as fine as 7 μm. Crosssections showed dense, fine-grained Cu with no cracks and minimal porosity. Electron Diffraction Spectroscopy (EDS) confirmed the high-purity of the EP Cu. Adhesion testing (ASTM D3359) achieved a B4 rating (<5% Cu removal). Test coupons survived both 10,000 robotic dynamic 180° bending cycles on 10 mm radius-of-curvature (RoC) mandrels at 30 cycles/min., and 100 hr. static bending on 10 mm RoC mandrels with <5% increases in electrical resistance. Subsequent (in-progress) testing includes flexing at additional strain rates (various RoC’s), torsion, and environmental exposures. Future work will extend from this single-layer TV circuit design on PET to a two-layer TV design with metal-filled conductive through-vias. The ultimate goal of this work is the R2R-fabrication of a two circuit-layer NextFlex A21LG microcontroller module on PET: A FHE device previously built by NextFlex in panel-format on Kapton HN Polyimide substrate.

Interest in advanced driver assistance systems (ADAS) is booming in recent years. One of the most effervescent ADAS features is blind spot detection (BSD), which uses radar sensors or cameras to detect vehicles in the blind spot area and alerts the driver to avoid a collision when changing lanes. However, this kind of BSD system fails to notify nearby vehicle drivers in this blind spot of the possible collision. The goal of this research is to design a proactive bus blind spot warning (PBSW) system that will immediately notify motorcyclists when they enter the blind spot or the area of the inner wheel difference of a target vehicle, i.e., a bus. This will increase the real-time functionality of BSD and can have a significant impact on enhancing motorcyclist safety. The proposed hardware is placed on the motorcycle and consists of a Raspberry Pi 3B+ and a dual-lens stereo camera. We use dual-lens cameras to capture and create stereoscopic images then transmit the images from the Raspberry Pi 3B+ to an Android phone via Wi-Fi and to a cloud server using a cellular network. At the cloud server, we use the YOLOv4 image recognition model to identify the position of the rear-view mirror of the bus and use the lens imaging principle to estimate the distance between the bus and the motorcyclist. Finally, the cloud server returns the estimated distance to the PBSW app on the Android phone. According to the received distance value, the app will display the visible area/blind spot, the area of the inner wheel difference of the bus, the position of the motorcyclist, and the estimated distance between the motorcycle and the bus. Hence, as soon as the motorcyclist enters the blind spot of the bus or the area of the inner wheel difference, the app will alert the motorcyclist immediately to enhance their real-time safety. We have evaluated this PBSW system implemented in real life. The results show that the average position accuracy of the rear-view mirror is 92.82%, the error rate of the estimated distance between the rear-view mirror and the dual-lens camera is lower than 0.2%, and the average round trip delay between the Android phone and the cloud server is about 0.5 s. To the best of our knowledge, this proposed system is one of few PBSW systems which can be applied in the real world to protect motorcyclists from the danger of entering the blind spot and the area of the inner wheel difference of the target vehicle in real time.

The goal of this research is to design a proactive bus blind spot warning (PBSW) system which will notify the motorcycle riders as soon as they enter the blind spot of a target vehicle, i.e., bus. The motorcycle side of this PBSW system, consisting of a Raspberry Pi 3B+ and a dual-lens stereo camera, will first transmit captured images to the Android phone using Wi-Fi and then to the cloud server through the cellular network. At the cloud server, the famous AI model, YOLOv4, is used to recognize the position of the rear-view mirror of the bus. By the principle of lens imaging, the distance between the bus and the motorcycle is estimated. Based on the estimated distance returned from the cloud server, the PBSW APP running in the Android phone illustrates the visible area/blind spot of the bus, the position of the rider and the estimated distance between the motorcycle and the bus. It further alarms the rider whenever the rider has entered the blind spot of the bus. According to performance evaluation on this implemented system, it recognizes the rear-view mirror with the average accuracy of 92.82%, the error rate of the estimated distance lower than 0.2% and the average round trip delay of 0.5 sec. It is concluded that this PBSW system keeps the motorcycle rider away from imminent dangers in real time.

Unique and random wrinkle features are desired for applications, especially in anticounterfeiting. Multifunctional wrinkled materials as well as simple wrinkling methods are desired for more applications. In this study, free-standing wrinkle-patterned porous polymer films were prepared using a modified supercritical CO2 foaming strategy. Spontaneous wrinkling was generated by applying moderate normal stress to the polymer films while foaming in situ. The wrinkle characteristics (wavelength and amplitude) were shown to be governed by the film thickness and the magnitude of the applied stress. Excessive (>5000 N) or no stress produced no obvious wrinkling or foaming whatsoever. Moreover, different morphologies of the wrinkles such as brain coral and herringbone patterns were achieved depending upon the shape of the mold used to apply the stress. Thus, the patterns show unique features for each batch process. Notwithstanding, geometric shape of the foamed wrinkle area is customizable. The reported wrinkling strategy offers the complementary advantage of patterning a foam in a polymer film and templating a PDMS stamp for different applications such as "mask-less" soft lithography, anticounterfeiting, pattern transfer, flexographic printing, and displays.