Vacuum-filling of liquid metals for 3D printed RF antennas

Bharambe, Vivek T.; Parekh, Dishit P.; Ladd, Collin; Moussa, K.; Dickey, Michael D.; Adams, Jack A.

doi:10.1016/j.addma.2017.10.012

Cited by 44 publications

(44 citation statements)

References 26 publications

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“…The results are consistent with the simulation with only a slight deviation due to the interference of the outer epoxy shell. Our antenna differs from other adaptive antenna in its active shape morphing capability and the as printed 3D shape, making it uniquely appealing for applications that require these two attributes.…”

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confidence: 99%

Rapid Open‐Air Digital Light 3D Printing of Thermoplastic Polymer

et al. 2019

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printing is, however, limited by various factors, with printing speed and material versatility being the most decisive. From the standpoint of printing speed, layerwise printing by digital light processing (DLP) offers significant inherent advantage over point-wise printing by most other methods such as fused deposition modeling (FDM) and stereolithography (SLA). [20] Further innovations on DLP such as continuous building in the z-dimension allow achieving a printing speed far exceeding any other methods. [21][22][23] Recent attempt on direct forming 3D object in a volumetric fashion forgoes even the layer-wise printing, but the technique has yet to evolve into the mainstream. [24,25] Generally, DLP employs light curable liquid resins. Upon digital light exposure, the resin cross-links and forms a thermoset polymer that ensures its separation from the surrounding liquid precursors. This rapid liquid-solid separation is the key enabling characteristic for DLP. Although cross-linking ensures such, the resulting thermoset polymers cannot be reprocessed. This prohibits its broader utility in situations that require further processing of the printed materials. In principle, this limitation can be overcome if the DLP processing can be extended to reprocessable thermoplastic polymers. Although light curable thermoplastic polymers are known, meeting the unique DLP requirement for rapid separation between the liquid monomer and the un-crosslinked polymer is not straightforward because of their intrinsic good miscibility. Hereafter, we describe our successful attempt in DLP printing of a thermoplastic polymer and lay out key enabling factors for such a process. We further illustrate that the water dissolvable nature of the resulting polymer is advantageous in making various multifunctional 3D structures. We find that the oxygen naturally present in ambient air can inhibit the light curing process. This effect can be utilized to achieve rapid open-air printing without the complex interfacial engineering typically required for fast DLP printing methods. [21][22][23] We hypothesize that two key factors should be carefully considered for DLP printing of thermoplastic polymers (Figure 1a). Herein, two concurrent and competing processes occur: 1) the polymerization and 2) the diffusion/dissolution of the polymer into the surrounding uncured liquid monomer. Rapid liquidsolid separation is possible only if the first process dominates 3D printing has witnessed a new era in which highly complexed customized products become reality. Realizing its ultimate potential requires simultaneous attainment of both printing speed and product versatility. Among various printing techniques, digital light processing (DLP) stands out in its high speed but is limited to intractable light curable thermosets. Thermoplastic polymers, despite their reprocessibility that allows more options for further manipulation, are restricted to intrinsically slow printing methods such as fused deposition modeling. Extending DLP to thermoplastics is highly desirabl...

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Rapid Open‐Air Digital Light 3D Printing of Thermoplastic Polymer

et al. 2019

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“…In [ 201 ], the EGaIn was 3D printed utilizing VeroClear material to design the antenna with slots. In the meantime, in [ 202 ], a Visijet M3-type Crystal was 3D printed using the EGaIn radiator to design a planar helical antenna. Thus, the substrate was 3D printed, and the LM was created into its cavities using the vacuum-based filling method.…”

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confidence: 99%

Recent Advances of Wearable Antennas in Materials, Fabrication Methods, Designs, and Their Applications: State-of-the-Art

et al. 2020

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The demand for wearable technologies has grown tremendously in recent years. Wearable antennas are used for various applications, in many cases within the context of wireless body area networks (WBAN). In WBAN, the presence of the human body poses a significant challenge to the wearable antennas. Specifically, such requirements are required to be considered on a priority basis in the wearable antennas, such as structural deformation, precision, and accuracy in fabrication methods and their size. Various researchers are active in this field and, accordingly, some significant progress has been achieved recently. This article attempts to critically review the wearable antennas especially in light of new materials and fabrication methods, and novel designs, such as miniaturized button antennas and miniaturized single and multi-band antennas, and their unique smart applications in WBAN. Finally, the conclusion has been drawn with respect to some future directions.

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“…Here, RT Duroid 5880 is a printed circuit board (PCB)-like commercially available high-frequency laminate formed by polytetrafluoroethylene (PTFE) composites reinforced with glass microfibers while VeroClear is a commercially available acrylic-based rigid material used for 3D printing of optically clear structures. Another 3D-printed rigid substrate material is VisiJet M3 Crystal which was used in [39] to develop a planar patch and helical antenna using a vacuum filling technique. Meanwhile in [9], Rogers 4003C rigid substrate was milled before a second top cover made of the same material was glued to the first one, forming a sealed fluidic channel.…”

Section: Substrate Materialsmentioning

confidence: 99%

“…Similarly, microfluidic channels for EGaIn were 3D printed using VeroClear substrate to form a patch antenna with switchable slots (PASS) [38]. Meanwhile, in [39], Visijet M3 Crystal, a commercially available photocurable resin, was 3D printed to form planar and helical antennas with EGaIn as the radiative element. Once the substrate was 3D printed and the supporting structure was properly dissolved, LM was introduced into its cavities using a vacuum filling technique.…”

Section: Printingmentioning

confidence: 99%

Liquid Metal Antennas: Materials, Fabrication and Applications

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Butt

Alghamdi

et al. 2019

Sensors

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This work reviews design aspects of liquid metal antennas and their corresponding applications. In the age of modern wireless communication technologies, adaptability and versatility have become highly attractive features of any communication device. Compared to traditional conductors like copper, the flow property and lack of elasticity limit of conductive fluids, makes them an ideal alternative for applications demanding mechanically flexible antennas. These fluidic properties also allow innovative antenna fabrication techniques like 3D printing, injecting, or spraying the conductive fluid on rigid/flexible substrates. Such fluids can also be easily manipulated to implement reconfigurability in liquid antennas using methods like micro pumping or electrochemically controlled capillary action as compared to traditional approaches like high-frequency switching. In this work, we discuss attributes of widely used conductive fluids, their novel patterning/fabrication techniques, and their corresponding state-of-the-art applications.Most of the conventional antennas are fabricated by etching the copper cladding on the rigid substrates to form static conductor shapes. Such antennas are highly efficient but suffer from irreversible structure deformation and even damage when being bent or stretched beyond certain limits [3]. As alternatives, several types of copper-coated polymer substrates such as Kapton, polyethylene terephthalate (PET), and polyethylene naphthalate (PEN) films have been investigated to accommodate the need in flexible applications such as antennas. Similar to conventional substrates, the electrical properties of these substrates also degrade after severe bending/stretching, which in turn reduces antenna efficiency. Another option is polymer-based materials such as polydimethylsiloxane (PDMS), which has been typically used in combination with copper foils to realize highly flexible antennas. However, the semi-rigid copper foils may potentially suffer from irreversible deformation after certain bending cycles. Alternatively, liquid metals can be injected into microfluidic channels to fabricate highly flexible and mechanically stable antennas without compromising their electrical properties [4].In [5], a broader review of fluidics-based tuning methods for the development of microwave components was presented. Although, this included a review of antennas based on dielectric/conductive fluids, it primarily covered flexible and frequency-tunable antenna/arrays and lacked depth on polarization/pattern reconfigurability techniques. Additionally, discussion of recent advancements in state-of-the-art liquid metal applications was also missing in [5]. In [6], a mini review of flexible and stretchable antennas based on textile materials was discussed. Here, the focus was on the benefits of conductive filler-based elastomers used in antennas for bio-integrated electronics applications and the trade-off between antenna stretchability and its performance. However, a detailed review of materials, novel fabrication te...

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Vacuum-filling of liquid metals for 3D printed RF antennas

Cited by 44 publications

References 26 publications

Rapid Open‐Air Digital Light 3D Printing of Thermoplastic Polymer

Rapid Open‐Air Digital Light 3D Printing of Thermoplastic Polymer

Recent Advances of Wearable Antennas in Materials, Fabrication Methods, Designs, and Their Applications: State-of-the-Art

Liquid Metal Antennas: Materials, Fabrication and Applications

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