Soft Systems Group Presentations

Controlled shaping of sessile magnetic drops - Jeniffer Dodoo

Controlled shaping of droplets is used in digital microfluidics to manipulate droplets for mixing and sensing. Droplets can be shaped through the application of electromagnetic fields, which exert a force on ions or electric and magnetic dipoles in the droplet. This force can be calculated using the electromagnetic stress tensor, which is a powerful tool derived from the first principles of electromagnetism and thermodynamics. The electromagnetic stress tensor in vacuum has been applied to a limited set of well-defined problems such as electrowetting, a technique where surface energies of the substrate are electrostatically modified.

Electric actuation techniques are well studied and widely adopted. In contrast, relatively little work exists on magnetic actuation techniques, such as the actuation of paramagnetic salt solutions, which has been demonstrated on superhydrophobic surfaces. Since magnetic actuation techniques require the presence of magnetic dipoles, they open a range of new possibilities for sensing and measurement applications.

Here, we explicitly apply the electromagnetic stress tensor to a sessile droplet in a homogeneous magnetic field and derive a relationship for the change in droplet shape as a function of applied magnetic field. We validate this relationship experimentally, by measuring the change in shape of a paramagnetic sessile droplet in a magnetic field and showcase its potential by demonstrating lateral movement and mixing of paramagnetic droplets. Our results demonstrate the controlled shaping and manipulating of magnetic droplets while highlighting the fundamental physics involved in these interactions.

A modular robotic sorting table - Ross McKensie

Applications such as recycling and shipping require the rapid sorting of heterogeneous objects against multiple criteria. Many of these objects also present difficult robotic grasping problems leading to the need for large workforces working under poor conditions to fulfill the current demand for recycling and shipping.

Current high-throughput industrial sorting methods are designed for a narrow range of objects to be sorted and sorting criteria to be used. Robotic, peristaltic conveyance can be used for the parallel sorting of a wide variety of objects with different criteria. Peristaltic sorting can also handle delicate and non-rigid objects. Current implementations of peristaltic sorting have been limited by their reliance on central systems to control many actuators.

In this presentation I detail my work on a peristaltic sorting table made from 25 modular robots using a distributed sorting algorithm. This table is scalable and perform a variety of sorting and conveyance actions.