Advisor: Young-Hui Chang , Ph.D. (Georgia Institute of Technology)
Jonathan S. Colton, Ph.D. (Georgia Institute of Technology)
Geza Kogler, Ph.D. (Georgia Institute of Technology)
Design and Prototyping of a Granular Foot Orthosis (FootGO)
Foot orthoses are assistive devices that are widely used to treat, alter, and in some cases correct different foot disorders. Inconsistencies during their manufacturing process can lead to ill-fitting orthoses, meaning that the clinician must go through many iterations to arrive at a properly formed insole. Iterative orthosis fabrication leads to extra cost, waste of materials, and increased lead time to help the patient. In addition to these front-end concerns, material durability during use is a major issue. To minimize these issues, we proposed to design a novel orthosis that utilizes granular jamming technology. I hypothesize that the Foot Granular Orthosis (FootGO), will exhibit tunable stiffness properties (by means of adjusting the vacuum pressure on the system) that allow it to mimic the material behavior of a wide range of commercial orthotic foams in a single generic device. Three types of granular media were used in different prototype compositions based on varying volume fill, particulate size, and granular media type. We conducted a series of uniaxial compression tests on a selection of foams as well as the newly designed FootGO prototypes, and obtained stress-strain curves from this data. Most of the prototypes agreed with expected material behavior trends. The energy absorption for each specimen, both foam and prototype, was then determined. The FootGO showed indications of superior durability through consistent results over repeated tests. The range of energy absorption performance for each FootGO prototype was compared to the range for commercial foams. The FootGO prototypes spanned the range over the various negative pressures, some of them extending well beyond the upper limit of the foam performance band. These findings imply that varying the negative pressure within the FootGO produces corresponding adjustable stiffness properties and that the FootGO can potentially mimic the behavior of a wide range of orthotic materials.