AI 中文总结
该研究证实活性微泳动体可强化致密乳状液，其源于微泳动体活性而非内含物存在，揭示了微结构与微泳动体间的反馈回路，为调控无序软固体力学提供了模型平台。
AI 中文摘要
我们证实，活性微泳动体可从力学层面强化致密乳状液。在跨越堵塞转变的宽范围油分数下，我们对比了三种状态下含微藻莱茵衣藻（Chlamydomonas reinhardtii）的蓖麻油-水乳状液：无藻状态、固定藻状态及运动藻状态。振荡流变学测试显示，运动藻可系统性提升乳状液的屈服应力，增幅最高达2倍；而相同浓度下的固定藻细胞对屈服应力基本无影响，因此这种强化作用源于微泳动体的活性，而非仅因内含物的存在。单细胞追踪结果表明，油滴网络将微泳动体限制在随油分数增大而收缩的孔隙中，而已有研究证实这种限制会放大莱茵衣藻的推进力。基于该限制增强力的简单估算可解释测得的额外屈服应力，且表明被动油滴间存在由活性诱导的类排空有效吸引力。这些结果揭示了一个反馈回路：微结构限制微泳动体，限制作用放大其施加的力，而这些力又会使微结构硬化。因此，活性乳状液有望成为通过活性调控无序软固体力学性质的模型平台。
英文摘要
We show that living microswimmers mechanically reinforce dense emulsions. Castor-oil-in-water emulsions laden with the microalga Chlamydomonas reinhardtii are compared in three states: without algae, with immobilized algae, and with motile algae, over a broad range of oil fractions spanning the jamming transition. Oscillatory rheology reveals that motile algae systematically increase the yield stress, by up to a factor of two, whereas immobilized cells at the same concentration leave it essentially unchanged. The reinforcement thus originates from activity rather than from the mere presence of inclusions. Single-cell tracking shows that the droplet network confines the swimmers in pores that shrink as the oil fraction increases, and confinement is known to amplify the propulsion force of C. reinhardtii. A simple estimate based on this confinement-enhanced force accounts for the measured excess yield stress and indicates an effective, activity-induced depletion-like attraction between the passive droplets. These results identify a feedback loop: the microstructure confines the swimmers, confinement amplifies the forces they exert, and these forces stiffen the microstructure. Active emulsions thus emerge as a model platform for programming the mechanics of disordered soft solids through activity.
Comments12 pages, 8 figures
