@article{joshipura_nguyen_quinn_yang_morales_santiso_daeneke_truong_dickey_2023, title={An atomically smooth container: Can the native oxide promote supercooling of liquid gallium?}, volume={26}, ISSN={["2589-0042"]}, url={https://doi.org/10.1016/j.isci.2023.106493}, DOI={10.1016/j.isci.2023.106493}, abstractNote={Metals tend to supercool—that is, they freeze at temperatures below their melting points. In general, supercooling is less favorable when liquids are in contact with nucleation sites such as rough surfaces. Interestingly, bulk gallium (Ga) can significantly supercool, even when it is in contact with heterogeneous surfaces that could provide nucleation sites. We hypothesized that the native oxide on Ga provides an atomically smooth interface that prevents Ga from directly contacting surfaces, and thereby promotes supercooling. Although many metals form surface oxides, Ga is a convenient metal for studying supercooling because its melting point of 29.8°C is near room temperature. Using differential scanning calorimetry (DSC), we show that freezing of Ga with the oxide occurs at a lower temperature (−15.6 ± 3.5°C) than without the oxide (6.9 ± 2.0°C when the oxide is removed by HCl). We also demonstrate that the oxide enhances supercooling via macroscopic observations of freezing. These findings explain why Ga supercools and have implications for emerging applications of Ga that rely on it staying in the liquid state.}, number={4}, journal={ISCIENCE}, author={Joshipura, Ishan D. and Nguyen, Chung Kim and Quinn, Colette and Yang, Jiayi and Morales, Daniel H. and Santiso, Erik and Daeneke, Torben and Truong, Vi Khanh and Dickey, Michael D.}, year={2023}, month={Apr} }
 @article{wu_li_zhao_zhang_xiong_yu_dickey_yang_2023, title={Convex Microarrays-Based Liquid Metal Soft Piezoresistive Stress Sensor With High Sensitivity and Large Measurement Range}, volume={23}, ISSN={["1558-1748"]}, url={https://doi.org/10.1109/JSEN.2023.3260029}, DOI={10.1109/JSEN.2023.3260029}, abstractNote={Liquid metal (LM) soft piezoresistive sensors, that is, devices that change resistance in response to mechanical forces, have low hysteresis and high stability, which exhibit great promise for human health monitoring. Applying stress reduces the cross-sectional area of the LM conductive path in the sensor, increasing the resistance and enabling the measurement of stress. However, increasing the sensitivity of the sensor results in a reduced measurement range and an increase in the cost. To solve this problem, this article presents a convex microarrays (CMs)-based LM soft piezoresistive stress sensor with high sensitivity and large measurement range. The CMs are located inside the microchannel, which improves the sensitivity of the sensor without reducing the measurement range. The CMs also enable the sensor to monitor bending. The mechanism of the CMs is verified by theoretical analysis, finite element simulation, and experiments. The relationship between the height of the CMs and the sensitivity is investigated. The sensor can be used in the field of human health monitoring.}, number={9}, journal={IEEE SENSORS JOURNAL}, author={Wu, Yali and Li, Shuai and Zhao, Zibing and Zhang, Dongguang and Xiong, Xiaoyan and Yu, Tingting and Dickey, Michael D. and Yang, Jiayi}, year={2023}, month={May}, pages={9176–9182} }
 @article{yang_nithyanandam_kanetkar_kwon_ma_im_oh_shamsi_wilkins_daniele_et al._2023, title={Liquid Metal Coated Textiles with Autonomous Electrical Healing and Antibacterial Properties}, volume={4}, ISSN={["2365-709X"]}, DOI={10.1002/admt.202202183}, abstractNote={Conductive textiles are promising for human–machine interfaces and wearable electronics. A simple way to create conductive textiles by coating fabric with liquid metal (LM) particles is reported. The coating process involves dip‐coating the fabric into a suspension of LM particles at room temperature. Despite being coated uniformly after drying, the textiles remain electrically insulating due to the native oxide that forms on the LM particles. Yet, they can be rendered conductive by compressing the textile to rupture the oxide and thereby percolate the particles. Thus, compressing the textile with a patterned mold can pattern conductive circuits on the textile. The electrical conductivity of these circuits increases by coating more particles on the textile. Notably, the conductive patterns autonomously heal when cut by forming new conductive paths along the edge of the cut. The textiles prove to be useful as circuit interconnects, Joule heaters, and flexible electrodes to measure ECG signals. Further, the LM‐coated textiles provide antimicrobial protection against Pseudomonas aeruginosa and Staphylococcus aureus. Such simple coatings provide a route to convert otherwise insulating textiles into electrical circuits with the ability to autonomously heal and provide antimicrobial properties.}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Yang, Jiayi and Nithyanandam, Praneshnandan and Kanetkar, Shreyas and Kwon, Ki Yoon and Ma, Jinwoo and Im, Sooik and Oh, Ji-Hyun and Shamsi, Mohammad and Wilkins, Mike and Daniele, Michael and et al.}, year={2023}, month={Apr} }
 @article{kwon_cheeseman_frias‐de‐diego_hong_yang_jung_yin_murdoch_scholle_crook_et al._2021, title={A Liquid Metal Mediated Metallic Coating for Antimicrobial and Antiviral Fabrics}, volume={33}, ISSN={0935-9648 1521-4095}, url={http://dx.doi.org/10.1002/adma.202104298}, DOI={10.1002/adma.202104298}, abstractNote={Fabrics are widely used in hospitals and many other settings for bedding, clothing, and face masks; however, microbial pathogens can survive on surfaces for a long time, leading to microbial transmission. Coatings of metallic particles on fabrics have been widely used to eradicate pathogens. However, current metal particle coating technologies encounter numerous issues such as nonuniformity, processing complexity, and poor adhesion. To overcome these issues, an easy‐to‐control and straightforward method is reported to coat a wide range of fabrics by using gallium liquid metal (LM) particles to facilitate the deposition of liquid metal copper alloy (LMCu) particles. Gallium particles coated on the fabric provide nucleation sites for forming LMCu particles at room temperature via galvanic replacement of Cu2+ ions. The LM helps promote strong adhesion of the particles to the fabric. The presence of the LMCu particles can eradicate over 99% of pathogens (including bacteria, fungi, and viruses) within 5 min, which is significantly more effective than control samples coated with only Cu. The coating remains effective over multiple usages and against contaminated droplets and aerosols, such as those encountered in facemasks. This facile coating method is promising for generating robust antibacterial, antifungal, and antiviral fabrics and surfaces.}, number={45}, journal={Advanced Materials}, publisher={Wiley}, author={Kwon, Ki Yoon and Cheeseman, Samuel and Frias‐De‐Diego, Alba and Hong, Haeleen and Yang, Jiayi and Jung, Woojin and Yin, Hong and Murdoch, Billy J. and Scholle, Frank and Crook, Nathan and et al.}, year={2021}, month={Sep}, pages={2104298} }
 @article{neumann_kara_sargolzaeiaval_im_ma_yang_ozturk_dickey_2021, title={Aerosol Spray Deposition of Liquid Metal and Elastomer Coatings for Rapid Processing of Stretchable Electronics}, volume={12}, ISSN={["2072-666X"]}, url={https://doi.org/10.3390/mi12020146}, DOI={10.3390/mi12020146}, abstractNote={We report a spray deposition technique for patterning liquid metal alloys to form stretchable conductors, which can then be encapsulated in silicone elastomers via the same spraying procedure. While spraying has been used previously to deposit many materials, including liquid metals, this work focuses on quantifying the spraying process and combining it with silicones. Spraying generates liquid metal microparticles (~5 μm diameter) that pass through openings in a stencil to produce traces with high resolution (~300 µm resolution using stencils from a craft cutter) on a substrate. The spraying produces sufficient kinetic energy (~14 m/s) to distort the particles on impact, which allows them to merge together. This merging process depends on both particle size and velocity. Particles of similar size do not merge when cast as a film. Likewise, smaller particles (<1 µm) moving at the same speed do not rupture on impact either, though calculations suggest that such particles could rupture at higher velocities. The liquid metal features can be encased by spraying uncured silicone elastomer from a volatile solvent to form a conformal coating that does not disrupt the liquid metal features during spraying. Alternating layers of liquid metal and elastomer may be patterned sequentially to build multilayer devices, such as soft and stretchable sensors.}, number={2}, journal={MICROMACHINES}, publisher={MDPI AG}, author={Neumann, Taylor V. and Kara, Berra and Sargolzaeiaval, Yasaman and Im, Sooik and Ma, Jinwoo and Yang, Jiayi and Ozturk, Mehmet C. and Dickey, Michael D.}, year={2021}, month={Feb} }
 @article{lai_lu_wu_zhang_yang_ma_shamsi_vallem_dickey_2021, title={Elastic Multifunctional Liquid-Metal Fibers for Harvesting Mechanical and Electromagnetic Energy and as Self-Powered Sensors}, volume={11}, ISSN={["1614-6840"]}, DOI={10.1002/aenm.202100411}, abstractNote={Future wearable technologies and personal electronics may benefit from e‐textiles that simultaneously possess high elasticity and multiple capabilities such as energy harvesting and sensing. Here, the first elastic multifunctional fiber that can scavenge mechanical energy from body motion and electromagnetic energy from surrounding electrical appliances is presented. In addition to converting multiple sources of waste energy into electricity, the fibers can also serve as self‐powered tactile and biomechanical sensors. The fibers consist of hollow elastomeric fibers filled with liquid metal. The fibers harvest energy by the combination of triboelectricity (160 V m−1, 5 µA m−1, and ≈360 µW m−1) and induced electrification of the liquid metal (±8 V m−1 (60 Hz), ±1.4 µA m−1, and ≈8 µW m−1). The fibers are characterized and their utility for powering electronics and sensing biomechanical information is demonstrated. These fibers are further demonstrated as completely soft and stretchable components for human–machine interfaces, including keypads and wireless music controllers.}, number={18}, journal={ADVANCED ENERGY MATERIALS}, author={Lai, Ying-Chih and Lu, Hong-Wei and Wu, Hsing-Mei and Zhang, Dongguang and Yang, Jiayi and Ma, Jinwoo and Shamsi, Mohammad and Vallem, Veena and Dickey, Michael D.}, year={2021}, month={May} }
 @article{zhang_zhang_wu_xiong_yang_dickey_2021, title={Liquid Metal Interdigitated Capacitive Strain Sensor with Normal Stress Insensitivity}, volume={12}, ISSN={["2640-4567"]}, url={https://doi.org/10.1002/aisy.202100201}, DOI={10.1002/aisy.202100201}, abstractNote={Soft and stretchable sensors of strain are important for human–machine interfaces, soft robotics, and electronic skins. However, soft strain sensors generally cannot distinguish in‐plane strain from normal stress. For example, stretching a sensor often gives a similar signal to pressing the sensor. To solve this problem, a liquid metal (LM)‐interdigitated capacitive strain sensor that is insensitive to normal stress is introduced. The sensor contains LM‐interdigitated electrodes prepared by vacuum filling of LM into lithographically defined microchannels. The capacitance between the LM electrodes decreases with increasing strain due to geometric changes. Because of the liquid nature of the electrodes, the sensor exhibits high stretchability (100% strain) and repeatability with gauge factor of −0.3. Due to the elasticity of the device, the sensor has low hysteresis (<1%) and no crosstalk between strain and normal stress sensing. These types of soft sensors may find use in wearable devices.}, journal={ADVANCED INTELLIGENT SYSTEMS}, publisher={Wiley}, author={Zhang, Dongguang and Zhang, Jie and Wu, Yali and Xiong, Xiaoyan and Yang, Jiayi and Dickey, Michael D.}, year={2021}, month={Dec} }
 @article{yang_kwon_kanetkar_xing_nithyanandam_li_jung_gong_tuman_shen_et al._2021, title={Skin-Inspired Capacitive Stress Sensor with Large Dynamic Range via Bilayer Liquid Metal Elastomers}, volume={11}, ISSN={["2365-709X"]}, DOI={10.1002/admt.202101074}, abstractNote={Soft devices that sense touch are important for prosthetics, soft robotics, and electronic skins. One way to sense touch is to use a capacitor consisting of a soft dielectric layer sandwiched between two electrodes. Compressing the capacitor brings the electrodes closer together and thereby increases capacitance. Ideally, sensors of touch should have both large sensitivity and the ability to measure a wide range of stress (dynamic range). Although skin has such capabilities, it remains difficult to achieve both sensitivity and dynamic range in a single manmade sensor. Inspired by skin, this work reports a soft capacitive pressure sensor based on a bilayer of liquid metal elastomer foam (B‐LMEF). The B‐LMEF consists of an elastomer slab (elastic modulus: ≈655 kPa) laminated with a soft liquid metal elastomer foam (LMEF, elastic modulus: ≈7 kPa). The LMEF deforms at small stresses (<10 kPa), and both layers deform at large stresses (>10 kPa). The B‐LMEF has high sensitivity (0.073 kPa–1) at small stress and can operate over a large range of stress (200 kPa), which leads to a large dynamic range (≈4.1 × 105). Additionally, the elastomer slab has a large energy dissipation coefficient; the skin uses this property to cushion the human body from external stress and strain.}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Yang, Jiayi and Kwon, Ki Yoon and Kanetkar, Shreyas and Xing, Ruizhe and Nithyanandam, Praneshnandan and Li, Yang and Jung, Woojin and Gong, Wei and Tuman, Mary and Shen, Qingchen and et al.}, year={2021}, month={Nov} }
 @article{yang_tang_ao_ghosh_neumann_zhang_piskarev_yu_truong_xie_et al._2020, title={Ultrasoft Liquid Metal Elastomer Foams with Positive and Negative Piezopermittivity for Tactile Sensing}, volume={30}, ISSN={["1616-3028"]}, DOI={10.1002/adfm.202002611}, abstractNote={Soft, capacitive tactile (pressure) sensors are important for applications including human–machine interfaces, soft robots, and electronic skins. Such capacitors consist of two electrodes separated by a soft dielectric. Pressing the capacitor brings the electrodes closer together and thereby increases capacitance. Thus, sensitivity to a given force is maximized by using dielectric materials that are soft and have a high dielectric constant, yet such properties are often in conflict with each other. Here, a liquid metal elastomer foam (LMEF) is introduced that is extremely soft (elastic modulus 7.8 kPa), highly compressible (70% strain), and has a high permittivity. Compressing the LMEF displaces the air in the foam structure, increasing the permittivity over a large range (5.6–11.7). This is called “positive piezopermittivity.” Interestingly, it is discovered that the permittivity of such materials decreases (“negative piezopermittivity”) when compressed to large strain due to the geometric deformation of the liquid metal droplets. This mechanism is theoretically confirmed via electromagnetic theory, and finite element simulation. Using these materials, a soft tactile sensor with high sensitivity, high initial capacitance, and large capacitance change is demonstrated. In addition, a tactile sensor powered wirelessly (from 3 m away) with high power conversion efficiency (84%) is demonstrated.}, number={36}, journal={ADVANCED FUNCTIONAL MATERIALS}, author={Yang, Jiayi and Tang, David and Ao, Jinping and Ghosh, Tushar and Neumann, Taylor V. and Zhang, Dongguang and Piskarev, Yegor and Yu, Tingting and Truong, Vi Khanh and Xie, Kai and et al.}, year={2020}, month={Sep} }