Injection Of Liquid Metal Research Articles

Scalable Microwires through Thermal Drawing of Co-Extruded Liquid Metal and Thermoplastic Elastomer.

This article demonstrates scalable production of liquid metal (LM)-based microwires through the thermal drawing of extrudates. These extrudates were first co-extruded using a eutectic alloy of gallium and indium (EGaIn) as a core element and a thermoplastic elastomer, styrene-ethylene/butylene-styrene (SEBS), as a shell material. By varying the feed speed of the co-extruded materials and the drawing speed of the extrudate, it was possible to control the dimensions of the microwires, such as core diameter and shell thickness. How the extrusion temperature affects the dimensions of the microwire was also analyzed. The smallest microwire (core diameter: 52 ± 14 μm and shell thickness: 46 ± 10 μm) was produced from a drawing speed of 300.1 mm s-1 (the maximum attainable speed of the apparatus used), SEBS extrusion speed of 1.50 mm3 s-1, and LM injection rate of 5 × 105 μL s-1 at 190 °C extrusion temperature. The same extrusion condition without thermal drawing generated significantly large extrudates with a core diameter of 278 ± 26 μm and shell thickness of 430 ± 51 μm. The electrical properties of the microwires were also characterized under different degrees of stretching and wire kinking deformation which proved that these LM-based microwires change electrical resistance as they are deformed and fully self-heal once the load is removed. Finally, the sewability of these microwires was qualitatively tested by using a manual sewing machine to pattern microwires on a traditional cotton fabric.

Flexible and Stretchable Liquid‐Metal Microfluidic Electronics Using Directly Printed 3D Microchannel Networks

AbstractThis paper describes a method for fabricating microfluidic electronics with 3D interconnected networks by direct ink writing (DIW)‐based 3D printing. Existing 3D printing technologies have yet to simultaneously realize 1) direct printing of interconnected multilayered microchannels without supporting materials or post‐processing and 2) integration of electronic elements with microchannels during the process of printing. This research aims to develop a method to fabricate support‐free microchannels consisting of silicone sealant without the collapse of the extruded structure while integrating electronic elements during the fabrication by DIW. The injection of liquid metal into 3D‐printed microchannels allows the formation of electrical connections between 3D conductive networks and the embedded electronic elements, enabling the fabrication of flexible and stretchable liquid metal antenna coils. To demonstrate a practical application, 1) a skin‐attachable radio‐frequency identification (RFID) tag using a commercial skin‐adhesive plaster as a substrate and 2) free‐standing flexible wireless light‐emitting devices with a small footprint (21.4 mm × 15 mm) for potential implantable applications are produced. This technology will offer a new capability to realize the automated fabrication of stretchable printed circuits with 3D configuration of electrical circuits consisting of liquid metals.

Stretchable Sensors for Soft Robotic Grippers in Edge-Intelligent IoT Applications.

The rapid development of electronic material and sensing technology has enabled research to be conducted on liquid metal-based soft sensors. The application of soft sensors is widespread and has many applications in soft robotics, smart prosthetics, and human-machine interfaces, where these sensors can be integrated for precise and sensitive monitoring. Soft sensors can be easily integrated for soft robotic applications, where traditional sensors are incompatible with robotic applications as these types of sensors show large deformation and very flexible. These liquid-metal-based sensors have been widely used for biomedical, agricultural and underwater applications. In this research, we have designed and fabricated a novel soft sensor that yields microfluidic channel arrays embedded with liquid metal Galinstan alloy. First of all, the article presents different fabrication steps such as 3D modeling, printing, and liquid metal injection. Different sensing performances such as stretchability, linearity, and durability results are measured and characterized. The fabricated soft sensor demonstrated excellent stability and reliability and exhibited promising sensitivity with respect to different pressures and conditions.

Texture-structure-based liquid metal filling for blind-end microchannels and its application on multi-layer chips.

This research work reports a novel method to achieve fast liquid metal (LM) injection in blind-end microchannels which is especially suitable for multi-layer microfluidic chips. This method is based on a texture-like surface bonding technology. The texture-like surface is fabricated on a polydimethylsiloxane (PDMS) slab with standard soft-lithography technology and bonded with another PDMS slab with microelectrode patterns on it. When injected with LM, the texture-like structure can prevent the LM from entering but allows the air inside to be released during the injection to achieve perfect blind-end complex LM electrodes. The experimental results show that it can achieve fast and perfect LM injection in the blind-end pattern and can also prevent the large area of the flat chamber from collapsing during bonding. We also parametrically studied the texture structure's size for bonding strength between the texture structure and the blank PDMS surface. In addition, we integrate three layers of blind-end complex liquid metal patterns into one multi-layer chip using this technology and later use this structure to realize series connection of two LM-based electroosmotic micropumps (EOP). Compared with the conventional LM-based EOP, the structure of the EOP chip was greatly simplified and resulted in a higher level of integration.

Petrophysical characterization, BIB-SEM imaging, and permeability models of tight carbonates from the Upper Jurassic (Malm ß), SE Germany

Tight carbonate rocks are important hydrocarbon and potential geothermal reservoirs, for example, in CO2-Enhanced Geothermal Systems. We report a study of outcrop samples of tectonically undeformed tight carbonates from the upper Jurassic “Malm ß” formation in Southern Germany near the town of Simmelsdorf (38 km NE of Nuremberg) to understand bulk petrophysical properties in relation to microstructure and to compare models for permeability prediction in these samples. We applied Archimedes isopropanol immersion, Helium pycnometry, mercury injection, gamma density core logging, and gas permeability measurements, combined with microstructural investigations and liquid metal injection (LMI-BIB-SEM). In addition, ultrasonic velocity was measured to allow geomechanical comparison of stratigraphically equivalent rocks in the South German Molasse Basin (SGMB). Results show only small variations, showing that the formation is rather homogeneous with bulk porosities below 5% and argon permeabilities around 1.4E−17 m2. The presence of stylolites in some of the samples has neither a significant effect on porosity nor permeability. Pores are of submicron size with pore throats around 10 nm and connected as shown by Mercury injection and Liquid Metal injection. Samples have high dynamic Young’s Modulus of 73 ± 5 GPa as expected for lithified and diagenetically overmature limestones. Moreover, no trends in properties were observable toward the faults at meter scale, suggesting that faulting was post-diagenetic and that the matrix permeabilities were too low for intensive post-diagenetic fluid–rock interaction. Petrophysical properties are very close to those measured in the SGMB, illustrating the widespread homogeneity of these rocks and justifying the quarry as a reasonable reservoir analog. Permeability prediction models, such as the percolation theory-based Katz-Thompson Model, Poiseuille-based models, like the Winland, the Dastidar, the capillary tube, and the Kozeny-Carman Models, as well as several empirical models, namely, the Bohnsack, the Saki, and the GPPT Models, were applied. It is shown that the capillary tube Model and the Saki Model are best suited for permeability predictions from BIB-SEM and mercury injection capillary pressure results, respectively, providing a method to estimate permeability in the subsurface from drill cuttings. Matrix permeability is primarily controlled by the pore (throat) diameters rather than by the effective porosity.

Polarization-Reconfigurable Compact Wideband Slot Antenna by Using Liquid Metal

In this letter, a compact, low-profile, and wideband slot antenna with polarization reconfigurability is presented by using liquid metal (LM). A small rectangular ring placed below the microstrip line of a symmetric coplanar waveguide (CPW) is used for bandwidth enhancement. Three horizontal currents performed by LM injection are inserted for wide circular polarized excitation. The channel realized by three-dimensional printed technique is loaded on the antenna to provide reconfiguration conditions. By injecting the LM into the left or right channels, the radiation of right-hand circular polarization or left-hand circular polarization is achieved. While when the two channels are empty or both LM injections, the linear polarization (LP) radiations at two operating frequency bands are obtained. A prototype was fabricated and measured. Measurements show that the proposed antenna exhibits a wide impedance bandwidth (IBW) of 67% and an overlapped axial ratio bandwidth of 39.2% for the CP modes. While in the LP states, the overall reconfigurable IBW is 39.7%. Besides, the size of the antenna is 0.30 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.32 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.03 <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">λ</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> , which is quite compact and low-profile.

Reconfigurable Polarization Converter Using Liquid Metal Based Metasurface

A multifunctional reconfigurable metasurface based on liquid metal injection is presented. The reflective flexible material metasurface formed by two switchable microfluidic layers&#x2014; the top layer comprising an array of meandered half-rings and the lower layer, straight meander lines&#x2014;can be reconfigured into four states. The proposed metasurface becomes a reflector with emptied channels, whereas it exhibits linear-to-circular polarization conversion (or linear-to-cross-polarization conversion) properties when the top (or bottom) layer is filled with a liquid metal alloy. Upon normal excitation of linearly u/v-polarized waves and activation of the bottom layer, the metasurface reflects cross v/u-polarized waves in the frequencies from 9.83 to 17.42 GHz (53&#x0025; bandwidth) with a polarization conversion ratio (PCR) of at least 90&#x0025;. On the other hand, the metasurface operates as a linear-to-circular polarizer (for u/v-polarized waves) over 8.97&#x2013;11.30 GHz (23&#x0025; bandwidth), reflecting left- or right-hand circularly polarized waves. To verify the polarization conversion performance, a <inline-formula> <tex-math notation="LaTeX">$25\times 25$ </tex-math></inline-formula> element metasurface array is fabricated and measured. The experimental results confirm the simulation results over the 8&#x2013;12 GHz test band. The compactness, structural flexibility, and multifunctionality of the proposed metasurface make it a suitable candidate for modern integrated antenna array systems.

A High-Temperature and Frequency-Reconfigurable Multilayer Frequency Selective Surface Using Liquid Metal

A high-temperature and frequency-reconfigurable multilayer frequency selective surface (FSS) based on liquid metal is proposed in this work. After construction of a multilayer dielectric cavity with specific dielectric-shaped pillars and the injection of liquid metal (EGaIn) into each layer of the cavity, the liquid metal and dielectric pillars form a slot-type bandpass FSS, and frequency reconfiguration is realized by switching the injection layer. A prototype of the proposed FSS was designed, fabricated and measured. The measured results validated the design well. The good conductivity and fluidity of the liquid metal are utilized to realize the reconfigurable electromagnetic performance of the proposed FSS. This works in the C-band (5 GHz) and Ku band (13 GHz) and has a frequency switching time between 13.1 to 14.2 s. Moreover, due to the good thermal conductivity of liquid metal, the flowing liquid metal can take away heat, and the multilayer FSS can work as cooling plate. The heat transfer performance was investigated by numerical simulations. A 1000 ° plane heat source was set on the bottom surface of the double-layer FSS. The average temperature on the top surface was 62.2 °, when the liquid metal fluid in the FSS had a speed of 1 m/s. The proposed multilayer FSS has strong potential for applications in some special application fields involving stealth and hypersonic aircraft.

Soft Electrochemical/Electronic Devices and Their Applications in Point-of-Care Testing

Using soft materials (e.g., paper, hydrogel) to replace the traditional hard materials (e.g., glass, silicon) as substrates have become a recent trend in developing point-of-care testing (POCT) platforms. And through integration of the soft materials with electrochemical or electric devices can further extend the applications of POCT. In our recent work, we used four kinds of soft materials, including paper, PDMS, hydrogel and liquid marble, as the new soft substrates of POCT platforms and realized their new applications in POCT. For example, by integration of the electrodes and hydrophobic channels on paper through simply writing method using home-made pens, the fabricated paper-based electrochemical devices have been successfully applied to detect glucose in artificial urine and melamine in sample solutions. By fabrication of MWNTs/PDMS fibers as multifunctional sensors and integration them on a glove, the measurement of gesture recognition and temperature have been realized by the “smart” glove. Through injection of liquid metal into the 3D helical structure of hydrogel and combination the hydrogel with electronic sensing device, the temperature, UV sensing and EMG signal detections have been performed by the wearable, multifunctional hydrogel device. By using liquid marble as a separator and small device for isoelectric focusing, the POCT separation and analysis of proteins have been realized. The proposed new soft platforms show wide application potential in POCT.

Femtosecond laser hybrid fabrication of a 3D microfluidic chip for PCR application.

Microfluidic chips have gradually become a focus of scientific research. However, the fabrication of key functional components in microfluidic chips is always limited by the existing processing methods. The microfluidic chip is difficult to be three-dimensional (3D) and integrated. In response to the key problems of 3D integrated microfluidic chip fabrication, this paper presents a hybrid method for fabricating a microfluidic chip integrated 3D microchannels and metal microstructures by femtosecond laser wet etch technology and liquid metal injection. The integrated microfluidic chip fabricated by this method is expected to be applied to the core reaction unit of integrated PCR devices.

Soft Electrochemical/Electronic Devices and Their Applications in Point-of-Care Testing

Using soft materials (e.g., paper, hydrogel) to replace the traditional hard materials (e.g., glass, silicon) as substrates have become a recent trend in developing point-of-care testing (POCT) platforms. And through integration of the soft materials with electrochemical or electric devices can further extend the applications of POCT. In our recent work, we used four kinds of soft materials, including paper, PDMS, hydrogel and liquid marble, as the new soft substrates of POCT platforms and realized their new applications in POCT. For example, by integration of the electrodes and hydrophobic channels on paper through simply writing method using home-made pens, the fabricated paper-based electrochemical devices have been successfully applied to detect glucose in artificial urine and melamine in sample solutions. By fabrication of MWNTs/PDMS fibers as multifunctional sensors and integration them on a glove, the measurement of gesture recognition and temperature have been realized by the “smart” glove. Through injection of liquid metal into the 3D helical structure of hydrogel and combination the hydrogel with electronic sensing device, the temperature, UV sensing and EMG signal detections have been performed by the wearable, multifunctional hydrogel device. By using liquid marble as a separator and small device for isoelectric focusing, the POCT separation and analysis of proteins have been realized. The proposed new soft platforms show wide application potential in POCT.

A novel combination of graphene and silver nanowires for entirely stretchable and ultrasensitive strain sensors: sandwich-based sensing films

A great deal of engineering effort is focused on developing stretchable strain sensors for human motion monitoring and wearable devices. The ultrasensitivity and fast response under tiny strain (1%) while maintaining the working range remain the grand challenge. In this work, we propose an entirely stretchable strain sensor based on the sandwich sensing film, which is fabricated by vacuum filtration of silver nanowires (AgNWs)/ graphene/ AgNWs in sequence and the injection of liquid metal as electrodes. The novel sandwich sensing film endows the stretchable strain sensor high sensitivity under tiny strain (Gauge factor = 111.5 at 1%), fast response (<10 ms), relative large working range (0%–35%) with a maximum gauge factor of 1403.7, followed by good linearity, long-term durability, and the recovery property from being overstretched (>100%). The excellent performance is due to the slippage of the inner graphene under tiny strain, whereas the ‘sewing’ phenomenon of the outer AgNWs under larger strain. The sandwich structure illustrates a better combination of graphene and AgNWs than other hybrid methods, showing great potential in wearable devices and soft robotics.

Design of the Flowing LIquid Torus (FLIT)

Abstract The design of the F lowing LI quid T orus (FLIT) at Princeton Plasma Physics Laboratory (PPPL) is presented. FLIT will focus on the development of a liquid metal (LM) diagnostics and divertor system (without a plasma source) suitable for implementation in present-day fusion systems, such as NSTX-U. FLIT is intended to provide proof-of-concept for fast-flowing LM divertor designs for heat fluxes > 10 MW/m2. The toroidal test article (ID ≈ 0.56 m, OD ≈ 1.9 m, h ≈ 0.61 m) consists of 12 rectangular coils that can generate a centerline magnetic field of 1 T magnetic for greater than 10 s. Initially, 30 gallons Galinstan (Ga-In-Sn eutectic) will be recirculated within the test article using six jxB pumps to achieve flow velocities of up to 10 m/s across the fully annular radial test section. FLIT is designed to be a flexible machine that will allow experimental testing of various LM injection techniques, the study of flow instabilities, and electromagnetic control concepts to prove the feasibility of the LM divertors within fusion reactors.

Flow behavior of liquid metal in the connected fascial space: Intervaginal space injection in the rat wrist and mice with tumor

The fascia and the fascial space can help provide a better understanding of the body. An intervaginal space injection (ISI) provides unique advantages that require further investigation. An upper limb model including physiological conditions and the tumor process was chosen to determine the flow behavior of liquid metal after ISI. In normal rats, after the injection of liquid metal into the intervaginal space comprising tendons, vessels, and nerves, magnetic resonance imaging and an anatomy experiment indicated that the liquid metal wrapped around the fascial space and finally reached the fingertip downstream and the armpit upstream in addition to the neurovascular bundle without vessels or lymph nodes. Using environmental scanning electron microscopy (ESEM) images, we discovered that the liquid metal was wrapped around the fibers of the fascia and moved forward in microscale or nanoscale areas. These data confirmed a fascia-based pathway. In tumors, the liquid metal moved to the tumor capsule through the damaged spot, where cancer cells destroy the integrity of the fascia between the normal cells and cancer cells. The liquid metal partly wrapped around the tumor and separated the tumor from the surrounding normal muscle. The ESEM images showed that fibers of the fascia penetrated the tumor, thus forming a network through which the liquid metal penetrated the tumor. Our study illustrated the physiological and pathological flow behavior of liquid metal in the upper limb after ISI and demonstrated a nonvascular pathway in the fascia. ISI may be useful for clinical treatment in the fascial pathway.

3D printing for functional electronics by injection and package of liquid metals into channels of mechanical structures

With the fabrication freedom and high efficiency introduced by 3D printing, such technology has been explored in the electronic manufacturing processes. In the present work, we reported a developed method for the fabrication of functional electronics with liquid phase electronic circuits. The technique involves printing hollow channels within elastomer structures via fused deposition modeling (FDM), then injecting and encapsulating liquid metal to form electrical traces. The process parameters in printing elastomer objects and the design of hollow channels were investigated via the extrusion experiments. The influence of flow rates on liquid metal injection was also studied under pressure injection. Based on these discussions and validations, the relationships between process parameters and the printing structures were demonstrated, and the flexible substrate with hollow channels was successfully printed by optimization of the process parameters. Moreover, a probe signal circuit has been fabricated to demonstrate the ability of injecting and packaging liquid metal into 3D printed structures for functional electronics.

Development of a Multi-Stage Electroosmotic Flow Pump Using Liquid Metal Electrodes.

Injection of liquid metal into a polydimethylsiloxane (PDMS) channel can provide a simple, cheap, and fast method to fabricate a noncontact electrode for micro electroosmotic flow (EOF) pumps. In this study, a multi-stage EOF pump using liquid metal noncontact electrodes was proposed and demonstrated for high-flow-velocity applications. To test the pumping performance of this EOF pump and measure the flow velocity, fluorescent particles were added into deionized (DI) water to trace the flow. According to the experimental results, the pump with a five-stage design can drive a water flow of 5.57 μm/s at 10 V, while the PDMS gap between the electrode and the pumping channel is 20 μm. To provide the guidance for the pump design, parametric studies were performed and fully discussed, such as the PDMS gap, pumping channel dimension, and stage number. This multi-stage EOF pump shows potential for many high-flow-velocity microfluidic applications.

Sub-nanoliter nuclear magnetic resonance coils fabricated with multilayer soft lithography

We describe the fabrication and characterization of sub-nanoliter volume nuclear magnetic resonance (NMR) transceiver coils that are easily amenable to integration within PDMS-based microfluidics. NMR coils were constructed by the injection of liquid metal into solenoidal cavities created around a microchannel using consecutive replica molding and bonding of PDMS layers. This construction technique permits the integration of NMR coils with solenoidal, toroidal or other three-dimensional geometries within highly integrated microfluidic systems and are one step toward NMR-based chemical screening and analysis on chip. The current proof-of-principle implementation displays limited sensitivity and resolution due to the conductivity and magnetic susceptibilities of the construction materials. However, NMR measurements and finite-element simulations made with the current device geometry indicate that optimization of these materials will allow for the collection of spectra from sub-millimolar concentration samples in less than 1 nL of solution.

The squeeze infiltration process for fabrication of metal-matrix composites

This article relates to the fabrication of metal-matrix composites by the injection of liquid metal into a fibrous preform under an applied pressure. An analysis is presented describing the elastic deformation, fracture behavior, and melt infiltration characteristics of an assembly of fibers in an approximately planar random array. The predictions of a finite difference model describing the heat flow and solidification in the system are also examined. The predictions from the modeling are found to be broadly consistent with various types of experimental observation made with aluminum-based melts and fine δ alumina fibers. A number of microstructural features are examined and several recommendations put forward concerning optimization of microstructurevia control of processing parameters.