@article{mohammed_sundaresan_dickey_2015, title={Self-Running Liquid Metal Drops that Delaminate Metal Films at Record Velocities}, volume={7}, ISSN={["1944-8252"]}, DOI={10.1021/acsami.5b06978}, abstractNote={This paper describes a new method to spontaneously accelerate droplets of liquid metal (eutectic gallium indium, EGaIn) to extremely fast velocities through a liquid medium and along predefined metallic paths. The droplet wets a thin metal trace (a film ∼100 nm thick, ∼ 1 mm wide) and generates a force that simultaneously delaminates the trace from the substrate (enhanced by spontaneous electrochemical reactions) while accelerating the droplet along the trace. The formation of a surface oxide on EGaIn prevents it from moving, but the use of an acidic medium or application of a reducing bias to the trace continuously removes the oxide skin to enable motion. The trace ultimately provides a sacrificial pathway for the metal and provides a mm-scale mimic to the templates used to guide molecular motors found in biology (e.g., actin filaments). The liquid metal can accelerate along linear, curved and U-shaped traces as well as uphill on surfaces inclined by 30 degrees. The droplets can accelerate through a viscous medium up to 180 mm/sec which is almost double the highest reported speed for self-running liquid metal droplets. The actuation of microscale objects found in nature (e.g., cells, microorganisms) inspires new mechanisms, such as these, to manipulate small objects. Droplets that are metallic may find additional applications in reconfigurable circuits, optics, heat transfer elements, and transient electronic circuits; the paper demonstrates the latter.}, number={41}, journal={ACS APPLIED MATERIALS & INTERFACES}, publisher={American Chemical Society (ACS)}, author={Mohammed, Mohammed and Sundaresan, Rishi and Dickey, Michael D.}, year={2015}, month={Oct}, pages={23163–23171} }
 @article{mohammed_xenakis_dickey_2014, title={Production of Liquid Metal Spheres by Molding}, volume={4}, ISSN={["2075-4701"]}, DOI={10.3390/met4040465}, abstractNote={This paper demonstrates a molding technique for producing spheres composed of eutectic gallium-indium (EGaIn) with diameters ranging from hundreds of microns to a couple millimeters. The technique starts by spreading EGaIn across an elastomeric sheet featuring cylindrical reservoirs defined by replica molding. The metal flows into these features during spreading. The spontaneous formation of a thin oxide layer on the liquid metal keeps the metal flush inside these reservoirs. Subsequent exposure to acid removes the oxide and causes the metal to bead up into a sphere with a size dictated by the volume of the reservoirs. This technique allows for the production and patterning of droplets with a wide range of volumes, from tens of nanoliters up to a few microliters. EGaIn spheres can be embedded or encased subsequently in polymer matrices using this technique. These spheres may be useful as solder bumps, electrodes, thermal contacts or components in microfluidic devices (valves, switches, pumps). The ease of parallel-processing and the ability to control the location of the droplets during their formation distinguishes this technique.}, number={4}, journal={METALS}, publisher={MDPI AG}, author={Mohammed, Mohammed G. and Xenakis, Alexis and Dickey, Michael D.}, year={2014}, month={Dec}, pages={465–476} }
 @article{mohammed_dickey_2013, title={Strain-controlled diffraction of light from stretchable liquid metal micro-components}, volume={193}, ISSN={["0924-4247"]}, DOI={10.1016/j.sna.2013.01.031}, abstractNote={This paper elucidates and characterizes the origin of the spectrum of colors that appear on the surface of polydimethylsiloxane (PDMS) microchannels filled with liquid metal. The use of an oxygen plasma to seal the PDMS microchannels results in a thin oxide layer on the walls of the channels that buckles under compression to create diffractive corrugations. The liquid metal reflects the light from these corrugations. The thin layer of gallium oxide that forms on the metal improves the adhesion of the metal to the walls and thereby keeps it conformal with the corrugations during the buckling process. The conformal coating of metal makes the diffraction pattern more evident than if the metal was placed directly onto a pre-corrugated surface. This approach represents a simple method of fabricating soft diffractive elements with lithographically defined shapes that can be switched between a metallic and a colored state in response to compression; this feature may be used to sense compressive forces optically or for inherently aligned diffractive elements for optofluidics.}, journal={SENSORS AND ACTUATORS A-PHYSICAL}, publisher={Elsevier BV}, author={Mohammed, Mohammed G. and Dickey, Michael D.}, year={2013}, month={Apr}, pages={246–250} }