<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class="" style="font-family: HelveticaNeue;"><span class="">Dear Soft Matter Colleagues and Friends,</span></div><div class="" style="font-family: HelveticaNeue;"><span class=""><br class=""></span></div><div class=""><div class="" style="font-family: HelveticaNeue;">On Friday 21 April 2023 at 9:30 AM at the UW Faculty of Physics (Pasteura 5, Warsaw; room 1.40) we are hosting a seminar during which</div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class=""><b class="">Debasish Das </b>(University of Strathclyde, Glasgow)</font></div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">will give a talk</font></div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal; min-height: 14px;"><font face="HelveticaNeue" class=""><br class=""></font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class=""><b class="">On the absence of collective motion in a bulk suspension of spontaneously rotating dielectric particles</b></font></div></div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal;"><br class=""></div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal;"><b class="">Abstract</b></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><span class=""><font face="HelveticaNeue" class="">A suspension of dielectric particles rotating spontaneously when subjected to a DC electric field in two-dimensions next to a no-slip electrode have proven to be an ideal model for active matter [Bricard et al., 2013]. In this system, an electrohydrodynamic (EHD) instability called Quincke rotation was exploited to create self-propelling particles which aligned with each other due to EHD interactions giving rise to collective motion. It is natural to question whether a suspension of such particles in three-dimensions will also display collective motion and spontaneously flow like bacterial suspensions do. Using molecular dynamics type simulations, we show that dielectrophoretic forces responsible for chaining in the direction of the applied electric field in conventional electrorheological fluids prevent collective motion in suspensions with individual particle rotation. Our simulations discover that the fundamental microstructural unit of a suspension under Quincke rotation is a pair of counter-rotating spheres aligned in the direction of the electric field. We perform a linear stability that explains this observation [Das and Saintillan, 2023].</font></span></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><span class=""><font face="HelveticaNeue" class=""><br class=""></font></span></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><span class=""><font face="HelveticaNeue" class="">A. Bricard, J.-B. Caussin, N. Desreumaux, O. Dauchot, and D. Bartolo. Emergence of macroscopic directed motion in populations of motile colloids. Nature, 503:95–98, 2013.</font></span></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><span class=""><font face="HelveticaNeue" class=""><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;">D. Das and D. Saintillan. On the absence of collective motion in a bulk suspension of spontaneously rotating dielectric particles. sub judice, 2023.</div></font></span></div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal;"><div class="" style="margin: 0cm; background-color: white;"><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><br class=""></div></div></div><div class="" style="font-family: HelveticaNeue; margin: 0px; font-stretch: normal; line-height: normal;">We warmly welcome everyone to attend the talk and the Soft Matter Coffee Break after the seminar, held in room 2.63 (2nd floor).</div></div><div class="" style="font-family: HelveticaNeue;"><br class=""></div><div class="" style="font-family: HelveticaNeue;"><div dir="auto" class="" style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;"><div class=""><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Maria Ekiel-Jeżewska</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Maciej Lisicki</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Piotr Szymczak</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Panagiotis Theodorakis</font></div><div class="" style="margin: 0px; font-stretch: normal; line-height: normal;"><font face="HelveticaNeue" class="">Marek Trippenbach</font></div></div></div></div><div class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div dir="auto" style="caret-color: rgb(0, 0, 0); color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; text-decoration: none; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div style="color: rgb(0, 0, 0); letter-spacing: normal; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; word-spacing: 0px; -webkit-text-stroke-width: 0px; word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class=""><br class=""></div></div></div></div></div></div></div></div></div></div></div></div></div></div></div><div class=""><br class=""></div></div></div></body></html>