Janus particles
Microrollers flow uphill as granular media
Featured article in Nature Communications
Link to article: https://www.nature.com/articles/s41467-023-41327-1
Contact: Professor James Gilchrist, gilchrist@lehigh.edu
Significance:
This work helps us better understand granular physics by putting a different type of stress on the particles. Rather than having them flow due to gravity, each particle has a torque and a cohesive force that is based on the magnetic properties of the particles.
Never before has granular media been characterized as having a negative coefficient of friction
Work on microroller microbots is generally limited to single or binary interactions between particles. This work is the first to study them as a bulk material, which in turn, has novel properties.
Our lab has the ability to scale up microroller production to create larger quantities for use in a wide array of applications.
Press:
Original release: https://engineering.lehigh.edu/news/article/lehigh-researchers-make-sand-flows-uphill
University release: https://www2.lehigh.edu/news/defying-gravity-lehigh-researchers-discover-sand-that-flows-up
Selected by Nature.com as ""September's best science images"!"
https://www.nature.com/immersive/d41586-023-03066-7/index.html
-Selected by Nature's photo team
Other media:
https://arstechnica.com/science/2023/12/watch-sand-defy-gravity-and-flow-uphill-thanks-to-negative-friction/
https://le.ac.uk/news/2023/september/sand-microrollers#:~:text=A%20team%20of%20researchers%20including,in%20the%20journal%20Nature%20Communications.
https://phys.org/news/2023-09-sand-uphill.html
https://www.sciencedaily.com/releases/2023/09/230920152330.htm
https://www.realclearscience.com/2023/09/21/researchers_make_sand_that_flows_uphill_980934.html
https://www.eurekalert.org/news-releases/1002229
https://www.miragenews.com/lehigh-researchers-develop-uphill-flowing-sand-1088677/
https://cosmosmagazine.com/science/physics/sand-negative-friction-uphill-flow/
https://metroamericas.com/en/noticias-2/surprising-discovery-sand-can-flow-uphill/102626/
https://www.thedailyscience.org/engineers-discover-how-to-make-sand-flow-uphill.html
https://www.sciencetimes.com/articles/46095/20230920/sand-flow-uphill-engineering-researchers-discover.htm
https://tvn24.pl/tvnmeteo/nauka/piasek-wspinajacy-sie-do-gory-lamie-zasady-grawitacji-odkrycie-naukowcow-7354741 (in Polish)
https://www.innovations-report.com/materials-sciences/lehigh-university-researchers-make-sand-that-flows-uphill/
https://www.earth.com/news/defying-gravity-team-discovers-sand-that-can-flow-uphill/
https://oopstop.com/scientists-develop-sand-that-defies-gravity-by-flowing-uphill/
https://www.iflscience.com/sand-that-flows-uphill-created-by-researchers-70804
https://www.sciencealert.com/iron-coated-sand-made-to-flow-up-hill-in-strange-new-experiment
https://viralose.com/tag/uphill/
https://brasarr.com/iron-coated-sand-made-to-flow-uphill-in-strange-new-experiment-sciencealert-brasarr/
https://time.news/they-make-the-sand-move-upwards/
https://newsbeezer.com/canada/iron-coated-sand-flowed-up-hill-in-strange-new-experiment-sciencealert/
https://www.techexplorist.com/sand-flows-uphill/70707/
https://citylife.capetown/science/iron-coated-sand-made-to-flow-up-hill-in-strange-new-experiment/390855/
https://mydroll.com/researchers-make-sand-that-flows-uphill/
https://swifttelecast.com/researchers-make-sand-that-flows-uphill/
https://vervetimes.com/scientists-develop-sand-that-defies-gravity-by-flowing-uphill/
https://www.sott.net/article/484613-Negative-friction-sees-sand-flowing-uphill
https://physicsworld.com/a/sand-that-flows-uphill-handwritten-leds/
https://bnn.network/tech/innovations/engineering-the-impossible-sand-that-flows-uphill/
https://olhardigital.com.br/2023/09/22/ciencia-e-espaco/areia-estranha-criada-em-laboratorio-sobe-escada-e-paredes/ (Portuguese)
https://ng.24.hu/tudomany/2023/09/22/emelkedon-felfele-folyo-homokot-fejlesztettek/ (Hungarian)
https://styleguide.ro/nisip-acoperit-cu-fier-conceput-sa-curga-in-sus-de-deal-intr-un-nou-experiment-bizar-sciencealert/ (Romanian)
https://www.diariojaen.es/canales/trending/no-es-imposible-la-arena-tambien-puede-fluir-cuesta-arriba-LF9340490 (Spanish)
https://euro.eseuro.com/technology/1062747.html
https://tech.everyeye.it/notizie/materiale-sabbioso-scorre-sfidando-gravita-video-672561.html (Italian)
https://interestingengineering.com/science/miracle-or-not-magnetized-sand-flows-uphill-against-gravity
https://tecnoguide.info/lo-straordinario-video-di-un-nuovo-materiale-sabbioso-che-sfida-la-gravita/amp/ (Italian)
https://newsyou.info/en/2023/09/vcheni-viyavili-shho-pisok-spravdi-mozhe-tekti-vgoru (Russian)
https://news.knowledia.com/ZA/en/articles/iron-coated-sand-made-to-flow-up-hill-in-strange-new-experiment-422b2979fb761975e73c8f5c0e3a59f851a71119
https://curiosmos.com/sand-engineered-to-flow-uphill/
https://www.bizsiziz.com/miracle-or-not-magnetized-sand-flows-uphill-against-gravity/
https://www.technopixel.org/these-unusual-grains-of-sand-can-climb-uphill-and-up-walls/
https://www.gfp.asso.fr/archives/29032
https://news.knowledia.com/ZA/en/articles/iron-coated-sand-made-to-flow-up-hill-in-strange-new-experiment-422b2979fb761975e73c8f5c0e3a59f851a71119
https://www.youtube.com/watch?v=zlKBE3hic6A
https://www.newindianexpress.com/xplore/2023/sep/27/machine-learning-can-now-detect-alien-life-with-more-certainty-2618501.html
https://sputnikarabic.ae/20230923/%D8%B9%D9%84%D9%85%D8%A7%D8%A1-%D9%8A%D8%B7%D9%88%D8%B1%D9%88%D9%86-%D8%B1%D9%85%D8%A7%D9%84%D8%A7-%D9%85%D8%B7%D9%84%D9%8A%D8%A9-%D8%A8%D8%A7%D9%84%D8%AD%D8%AF%D9%8A%D8%AF-%D8%AA%D8%AA%D8%AF%D8%AD%D8%B1%D8%AC-%D8%A8%D8%B9%D9%83%D8%B3-%D8%A7%D9%84%D8%AC%D8%A7%D8%B0%D8%A8%D9%8A%D8%A9-%D9%81%D9%8A%D8%AF%D9%8A%D9%88-%D9%88%D8%B5%D9%88%D8%B1-1081319271.html (Arabic)
https://www.industrytap.com/believe-it-or-not-magnetized-sand-defies-gravity-and-flows-uphill/69146
Other resources:
All images/gifs on this website generated by the Gilchrist Lab are freely available
(please cite the paper and that the work was performed at Lehigh University)
BACKGROUND: Janus Particles
A quickly growing area of research in the Laboratory for Particle Mixing and Self-Organization
is the fabrication and development of Janus particles for various applications.
Below are descriptions and examples of the science/engineering enabled by Janus particles in our laboratory.
What are Janus particles?
Janus particles are spheres functionalized on one hemisphere of their surface to break symmetry and give particles two different physical/chemical/electromagnetic properties.
For example - a glass or polymer particle could be partially coated with a metal.
Microencapsulation of mobile field responsive Janus particle suspensions
https://pubs.rsc.org/en/content/articlelanding/2023/SM/D3SM00642E
Lehigh's Mountaintop Research Experience (Summer 2023)
Several Lehigh students contributed to research on Janus granular microrollers through doing fundamental research on granular media and how we can utilize these materials for various applications.
Granular Media
Granular media is interesting because of how it moves. As a solid that can behave as a liquid when in motion, its properties are currently being extensively studied. Granular media is particularly unique when it behaves as a liquid, so it is possible to derive velocity profiles for the moving grains. As well, these particles can also be fluidized when a fluid with a high enough velocity is passed through it, such that the particles behave much like a gas, with almost infinite kinetic collisions occurring between them. To initiate any kind of granular flow, a certain static threshold force must be overcome. Once this static force is overcome, in our case with a magnetic field, motion can be initiated and observed.
"Active Sands of Time": Altering the kinematics of flow down a funnel
The images below demonstrate how microrollers flow through a funnel. This device can study two funnel angles (one side has 90 degree right angles and the other has an angle just less than the passive angle of repose of the material. This work can lead to understand how optimize flow. (Work previously presented by UGs Brianna Sauders and Alex Oh and supported by Douglas Hardy).
Control
(no magnetic field)
Microrollers
rotating clockwise
Microrollers rotating
toward the center of the funnel