Activity and self-generated motion are fundamental features observed in many living and nonliving systems. Given that interparticle adhesive forces can regulate particle dynamics, we investigate how interparticle adhesion strength controls the boundary growth and roughness of active particle aggregates. Using particle based simulations incorporating both activity (birth, death, and growth) and systematic physical interactions (elasticity and adhesion), we establish that interparticle adhesion strength (f^ad) controls the surface roughness of a densely packed three-dimensional(3D) active particle aggregate expanding into a highly viscous medium. We discover that the surface roughness of a 3D active particle aggregate increases in proportion to the interparticle adhesion strength (f^ad) and show that asymmetry in the radial and transverse active particle mean-squared displacement (MSD) suppresses 3D surface roughness at lower adhesion strengths. By analyzing the statistical properties of particle displacements at the aggregate periphery, we determine that the 3D surface roughness is driven by the movement of active particle toward the core at high interparticle adhesion strengths. Our results elucidate the physics controlling the expansion of adhesive 3D active particle collectives into a highly viscous medium, with implications into understanding stochastic interface growth in active matter systems characterized by self-generation of particles.

中文翻译：

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颗粒间粘附调节生长致密三维活性颗粒聚集体的表面粗糙度

活动和自生运动是在许多生命和非生命系统中观察到的基本特征。鉴于颗粒间粘附力可以调节颗粒动力学，我们研究了颗粒间粘附强度如何控制活性颗粒聚集体的边界生长和粗糙度。使用包含活动（出生、死亡和生长）和系统物理相互作用（弹性和粘附力）的基于粒子的模拟，我们确定粒子间粘附强度 ( f ^ad ) 控制密集堆积的 3D (3D) 活性物质的表面粗糙度颗粒聚集体膨胀成高粘性介质。我们发现 3D 活性颗粒聚集体的表面粗糙度与颗粒间粘附强度 ( f^ad ) 并表明径向和横向活性粒子均方位移 (MSD) 的不对称性在较低的粘附强度下抑制了 3D 表面粗糙度。通过分析聚集体外围粒子位移的统计特性，我们确定 3D 表面粗糙度是由活性粒子在高粒子间粘附强度下向核心移动所驱动的。我们的研究结果阐明了控制粘性 3D 活性粒子集合膨胀成高粘性介质的物理原理，这对理解以粒子自生成为特征的活性物质系统中的随机界面生长具有重要意义。