title: A new bi-axial cantilever beam design for biomechanics force measurements.
abstract: The demand for measuring forces exerted by animals during locomotion has increased dramatically as biomechanists strive to understand and implement biomechanical control strategies. In particular, multi-axial force transducers are often required to capture animal limb coordination patterns. Most existing force transducers employ strain gages arranged in a Wheatstone bridge on a cantilever beam. Bi-axial measurements require duplicating this arrangement in the transverse direction. In this paper, we reveal a method to embed a Wheatstone bridge inside another to allow bi-axial measurements without additional strain gages or additional second beams. This hybrid configuration resolves two force components from a single bridge circuit and simplifies fabrication for the simultaneous assessment of normal and transverse loads. This design can be implemented with two-dimensional fabrication techniques and can even be used to modify a common full bridge cantilever force transducer. As a demonstration of the new design, we built a simple beam which achieved bi-axial sensing capability that outperformed a conventional half-bridge-per-axis bi-axial strain gage design. We have used this design to measure the ground reaction forces of a crawling caterpillar and a caterpillar-mimicking soft robot. The simplicity and increased sensitivity of this method could facilitate bi-axial force measurements for experimental biologists.
authors: Department of Biology, Tufts University, 163 Packard Avenue, Medford, MA 02155, USA. linh10@janelia.hhmi.org
authors: Huai-Ti
authors: HT
authors: Lin
authors: Barry A
authors: BA
authors: Trimmer
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D006614:Hindlimb / Q000502:physiology*; D008124:Locomotion / Q000502:physiology*; D008954:Models, Biological