Amphibious Articulating Foot Orthosis

This project focused on design thinking and creating a solution for a customer. My customer suffered from drop foot and wanted to continue swimming. With her current articulating foot orthotic (AFO), she was very limited in terms of how she could exercise. However, he used to be an avid swimmer and was eager to swim.

If someone suffered from dropfoot, swimming can often be painful. The inability to plantar-flex means that during the down stroke of the foot, the water resistance can hyper extend the ankle. Similarly, the inability to plantar-flex and stiffen the ankle can make it difficult to get in and out of a pool. This Amphibious AFO (AAFO) used a bi-stable mechanism to manually switch from plantar-flex to dorsi-flex when appropriate, allowing a user to both access a standard pool environent and swim in it. The large benefit of this is that this AAFO replaces the regular, daily-use AFO from the locker room (where the user changes into their bathing suit. Thus their daily AFO is not exposed to the elements of the pool.

The brace used a four-bar linkage to create the bi-stability in the ankle. A four-bar linkage us a closed link of four rods, where driving one rod can cause a second rod to rotate 360 degrees or sweep through a range of degrees, depending on the length of the rods and the starting position of the four-bar linkage. In the AAFO, two of the bars are accounted for by the shin and the foot, and the last two rods are physical rods that have a bias towards the two angles and thus snap into plantar- or dorsi-flexion.

The AAFO handles pretty well in the water.