Gravity can affect colloidal suspensions since for micrometer-sized particles gravitational and thermal energies can be comparable over vertical length scales of a few millimeters. In mixtures, each species possesses a different buoyant mass, which can make experimental results counter-intuitive and difficult to interpret. Here, we revisit from a theoretical perspective iconic sedimentation-diffusion-equilibrium experiments on colloidal plate-rod mixtures by van der Kooij and Lekkerkerker. We reproduce their findings, including the observation of five different mesophases in a single cuvette. Using sedimentation path theory, we incorporate gravity into a microscopic theory for the bulk of a plate-rod mixture. We also show how to disentangle the effects of gravity from sedimentation experiments to obtain the bulk behavior and make predictions that can be experimentally tested. These include changes in the sequence by altering the sample height. We demonstrate that both buoyant mass ratio and sample height form control parameters to study bulk phase behavior.

重力会影响胶体悬浮液，因为对于微米大小的颗粒，重力和热能在几毫米的垂直长度尺度上是相当的。在混合物中，每个物种都具有不同的浮力，这会使实验结果违反直觉且难以解释。在这里，我们从理论角度重新审视了 van der Kooij 和 Lekkerkerker 对胶体板棒混合物进行的标志性沉降-扩散-平衡实验。我们重现了他们的发现，包括在单个比色皿中观察到五个不同的中间相。使用沉降路径理论，我们将重力纳入了大量板棒混合物的微观理论。我们还展示了如何从沉降实验中解开重力的影响以获得整体行为并做出可以通过实验测试的预测。这些包括通过改变样品高度来改变序列。我们证明了浮力质量比和样品高度都形成了研究体相行为的控制参数。