@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{joshipura_persson_oh_kong_vong_ni_alsafatwi_parekh_zhao_dickey_2021, title={Are Contact Angle Measurements Useful for Oxide-Coated Liquid Metals?}, volume={37}, ISSN={["0743-7463"]}, DOI={10.1021/acs.langmuir.1c01173}, abstractNote={This work establishes that static contact angles for gallium-based liquid metals have no utility despite the continued and common use of such angles in the literature. In the presence of oxygen, these metals rapidly form a thin (∼1-3 nm) surface oxide "skin" that adheres to many surfaces and mechanically impedes its flow. This property is problematic for contact angle measurements, which presume the ability of liquids to flow freely to adopt shapes that minimize the interfacial energy. We show here that advancing angles for a metal are always high (>140°)-even on substrates to which it adheres-because the solid native oxide must rupture in tension to advance the contact line. The advancing angle for the metal depends subtly on the substrate surface chemistry but does not vary strongly with hydrophobicity of the substrate. During receding measurements, the metal droplet initially sags as the liquid withdraws from the "sac" formed by the skin and thus the contact area with the substrate initially increases despite its volumetric recession. The oxide pins at the perimeter of the deflated "sac" on all the surfaces are tested, except for certain rough surfaces. With additional withdrawal of the liquid metal, the pinned angle gets smaller until eventually the oxide "sac" collapses. Thus, static contact angles can be manipulated mechanically from 0° to >140° due to hysteresis and are therefore uninformative. We also provide recommendations and best practices for wetting experiments, which may find use in applications that use these alloys such as soft electronics, composites, and microfluidics.}, number={37}, journal={LANGMUIR}, author={Joshipura, Ishan D. and Persson, K. Alex and Oh, Ji-Hyun and Kong, Minsik and Vong, Man Hou and Ni, Chujun and Alsafatwi, Mohanad and Parekh, Dishit P. and Zhao, Hong and Dickey, Michael D.}, year={2021}, month={Sep}, pages={10914–10923} }
 @article{ma_bharambe_persson_bachmann_joshipura_kim_oh_patrick_adams_dickey_2021, title={Metallophobic Coatings to Enable Shape Reconfigurable Liquid Metal Inside 3D Printed Plastics}, volume={13}, ISSN={["1944-8252"]}, url={https://doi.org/10.1021/acsami.0c17283}, DOI={10.1021/acsami.0c17283}, abstractNote={Liquid metals adhere to most surfaces despite their high surface tension due to the presence of a native gallium oxide layer. The ability to change the shape of functional fluids within a three-dimensional (3D) printed part with respect to time is a type of four-dimensional printing, yet surface adhesion limits the ability to pump liquid metals in and out of cavities and channels without leaving residue. Rough surfaces prevent adhesion, but most methods to roughen surfaces are difficult or impossible to apply on the interior of parts. Here, we show that silica particles suspended in an appropriate solvent can be injected inside cavities to coat the walls. This technique creates a transparent, nanoscopically rough (10-100 nm scale) coating that prevents adhesion of liquid metals on various 3D printed plastics and commercial polymers. Liquid metals roll and even bounce off treated surfaces (the latter occurs even when dropped from heights as high as 70 cm). Moreover, the coating can be removed locally by laser ablation to create selective wetting regions for metal patterning on the exterior of plastics. To demonstrate the utility of the coating, liquid metals were dynamically actuated inside a 3D printed channel or chamber without pinning the oxide, thereby demonstrating electrical circuits that can be reconfigured repeatably.}, number={11}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Ma, Jinwoo and Bharambe, Vivek T. and Persson, Karl A. and Bachmann, Adam L. and Joshipura, Ishan D. and Kim, Jongbeom and Oh, Kyu Hwan and Patrick, Jason F. and Adams, Jacob J. and Dickey, Michael D.}, year={2021}, month={Mar}, pages={12709–12718} }
 @article{park_shintake_piskarev_wei_joshipura_frey_neumann_floreano_dickey_2021, title={Stretchable and Soft Electroadhesion Using Liquid-Metal Subsurface Microelectrodes}, volume={6}, ISSN={["2365-709X"]}, DOI={10.1002/admt.202100263}, abstractNote={Electroadhesion is an attractive mechanism to electrically modulate adhesion to surfaces. Electroadhesion arises from the interaction of electric fields with conductive or dielectric materials. Electroadhesion devices consist of in‐plane, interdigitated electrodes that generate out‐of‐plane electric fields, which increase adhesion with target surfaces. To date, these electrodes have predominantly been composed of carbonaceous materials. Here, liquid metal is utilized to create the electrodes in silicone substrates. Liquid metal can be patterned in a variety of unique ways, including microfluidic injection, spray deposition, or printing. These electrodes have nearly unlimited deformation in soft and stretchable substrates while maintaining metallic conductivity. The experimental results show that stretching improves electroadhesion performance due to the changes in geometry of the electrodes and insulation layer, whose behaviors are theoretically predictable. The use of liquid‐filled, sub‐surface microchannels can help to maintain contact between the elastomer and substrate during peeling due to the surface stresses caused by the capillary pressure. This approach to electroadhesion can be implemented in ultra‐stretchable and soft substrates, including those used in soft robotics, due to the inherently compliant and deformable electrical conductivity of the liquid metal electrodes.}, journal={ADVANCED MATERIALS TECHNOLOGIES}, author={Park, Sungjune and Shintake, Jun and Piskarev, Egor and Wei, Yuwen and Joshipura, Ishan and Frey, Ethan and Neumann, Taylor and Floreano, Dario and Dickey, Michael D.}, year={2021}, month={Jun} }
 @article{cooper_joshipura_parekh_norkett_mailen_miller_genzer_dickey_2019, title={Toughening stretchable fibers via serial fracturing of a metallic core}, volume={5}, ISSN={["2375-2548"]}, url={https://doi.org/10.1126/sciadv.aat4600}, DOI={10.1126/sciadv.aat4600}, abstractNote={Stretchable fibers dissipate energy via the sequential fracturing of a metallic core held together by an elastomeric shell. Tough, biological materials (e.g., collagen or titin) protect tissues from irreversible damage caused by external loads. Mimicking these protective properties is important in packaging and in emerging applications such as durable electronic skins and soft robotics. This paper reports the formation of tough, metamaterial-like core-shell fibers that maintain stress at the fracture strength of a metal throughout the strain of an elastomer. The shell experiences localized strain enhancements that cause the higher modulus core to fracture repeatedly, increasing the energy dissipated during extension. Normally, fractures are catastrophic. However, in this architecture, the fractures are localized to the core. In addition to dissipating energy, the metallic core provides electrical conductivity and enables repair of the fractured core for repeated use. The fibers are 2.5 times tougher than titin and hold more than 15,000 times their own weight for a period 100 times longer than a hollow elastomeric fiber.}, number={2}, journal={SCIENCE ADVANCES}, publisher={American Association for the Advancement of Science (AAAS)}, author={Cooper, Christopher B. and Joshipura, Ishan D. and Parekh, Dishit P. and Norkett, Justin and Mailen, Russell and Miller, Victoria M. and Genzer, Jan and Dickey, Michael D.}, year={2019}, month={Feb} }
 @inproceedings{reichel_lozada-smith_mendis_joshipura_dickey_mittleman_2017, title={Active THz waveguides enabled by liquid metal actuation}, DOI={10.1364/cleo_si.2017.sm3j.3}, abstractNote={We utilize electronically reconfigurable liquid metals to dynamically modify the coupling between two THz waveguides, to realize an active tunable filter with channel add-drop functionality.}, booktitle={2017 conference on lasers and electro-optics (cleo)}, author={Reichel, K. S. and Lozada-Smith, N. and Mendis, R. and Joshipura, I. and Dickey, Michael and Mittleman, D. M.}, year={2017} }
 @article{eaker_joshipura_maxwell_heikenfeld_dickey_2017, title={Electrowetting without external voltage using paint-on electrodes}, volume={17}, ISSN={["1473-0189"]}, DOI={10.1039/c6lc01500j}, abstractNote={Electrowetting uses voltage to manipulate small volumes of fluid for applications including lab-on-a-chip and optical devices. To avoid electrochemical reactions, a dielectric often separates the fluid from the electrode, which has the undesired effect of adding processing steps while increasing the voltage necessary for electrowetting. We present a new method to dramatically reduce the complexity of electrode and dielectric fabrication while enabling multiple performance advances. This method relies on a self-oxidizing paint-on liquid-metal electrode that can be fabricated in minutes on rigid, rough, or even elastic substrates, enabling low operation voltages (<1 V), and self-healing upon dielectric breakdown. Furthermore, due to the non-negligible 'potential of zero charge', electrowetting occurs by simply short circuiting the electrodes. This work opens up new application spaces for electrowetting (e.g. stretchable substrates, soft and injectable electrodes) while achieving large changes in contact angle without the need for an external power supply.}, number={6}, journal={LAB ON A CHIP}, publisher={Royal Society of Chemistry (RSC)}, author={Eaker, Collin B. and Joshipura, Ishan D. and Maxwell, Logan R. and Heikenfeld, Jason and Dickey, Michael D.}, year={2017}, month={Mar}, pages={1069–1075} }
 @article{eaker_joshipura_maxwell_heikenfeld_dickey_2017, title={Electrowetting without external voltage using paint-on electrodes (vol 17, pg 1069, 2017)}, volume={17}, ISSN={["1473-0189"]}, DOI={10.1039/c7lc90029e}, abstractNote={Correction for 'Electrowetting without external voltage using paint-on electrodes' by Collin B. Eaker et al., Lab Chip, 2017, DOI: .}, number={7}, journal={LAB ON A CHIP}, author={Eaker, Collin B. and Joshipura, Ishan D. and Maxwell, Logan R. and Heikenfeld, Jason and Dickey, Michael D.}, year={2017}, month={Apr}, pages={1359–1359} }
 @article{tang_joshipura_lin_kalantar-zadeh_mitchell_khoshmanesh_dickey_2016, title={Liquid-Metal Microdroplets Formed Dynamically with Electrical Control of Size and Rate}, volume={28}, ISSN={["1521-4095"]}, DOI={10.1002/adma.201503875}, abstractNote={Liquid metal co-injected with electrolyte through a microfluidic flow-focusing orifice forms droplets with diameters and production frequencies controlled in real time by voltage. Applying voltage to the liquid metal controls the interfacial tension via a combination of electrochemistry and electrocapillarity. This simple and effective method can instantaneously tune the size of the microdroplets, which has applications in composites, catalysts, and microsystems.}, number={4}, journal={ADVANCED MATERIALS}, publisher={Wiley}, author={Tang, Shi-Yang and Joshipura, Ishan D. and Lin, Yiliang and Kalantar-Zadeh, Kourosh and Mitchell, Arnan and Khoshmanesh, Khashayar and Dickey, Michael D.}, year={2016}, month={Jan}, pages={604–609} }
 @article{tang_lin_joshipura_khoshmanesh_dickey_2015, title={Steering liquid metal flow in microchannels using low voltages}, volume={15}, ISSN={["1473-0189"]}, DOI={10.1039/c5lc00742a}, abstractNote={Liquid metals based on gallium, such as eutectic gallium indium (EGaIn) and Galinstan, have been integrated as static components in microfluidic systems for a wide range of applications including soft electrodes, pumps, and stretchable electronics. However, there is also a possibility to continuously pump liquid metal into microchannels to create shape reconfigurable metallic structures. Enabling this concept necessitates a simple method to control dynamically the path the metal takes through branched microchannels with multiple outlets. This paper demonstrates a novel method for controlling the directional flow of EGaIn liquid metal in complex microfluidic networks by simply applying a low voltage to the metal. According to the polarity of the voltage applied between the inlet and an outlet, two distinct mechanisms can occur. The voltage can lower the interfacial tension of the metal via electrocapillarity to facilitate the flow of the metal towards outlets containing counter electrodes. Alternatively, the voltage can drive surface oxidation of the metal to form a mechanical impediment that redirects the movement of the metal towards alternative pathways. Thus, the method can be employed like a 'valve' to direct the pathway chosen by the metal without mechanical moving parts. The paper elucidates the operating mechanisms of this valving system and demonstrates proof-of-concept control over the flow of liquid metal towards single or multiple directions simultaneously. This method provides a simple route to direct the flow of liquid metal for applications in microfluidics, optics, electronics, and microelectromechanical systems.}, number={19}, journal={LAB ON A CHIP}, publisher={Royal Society of Chemistry (RSC)}, author={Tang, Shi-Yang and Lin, Yiliang and Joshipura, Ishan D. and Khoshmanesh, Khashayar and Dickey, Michael D.}, year={2015}, pages={3905–3911} }