Emerging Technologies Inspired by Plants - Bioinspired Approaches for Human-Centric Technologies - page 118

Fig. 4.4 A schematic representation of the differential growth response in plant roots (a) due to
the elongation at faster rates of cells in the region opposite to the direction of a stimulation in the
soil (hardness, water, temperature, etc.). In (b) a 3D representation of an artificial soft bending
mechanism with a tip is depicted. The system is actuated through the electrical control of three
fluid-filled chambers by means of ad hoc valves integrated at their back. The prototype is shown in
(c) where the right inset image depicts the soft flexible 8 mm 8 mm tactile sensor integrated at

the tip. Three of these tactile sensors are integrated in the artificial tip at 120 ; when they are
touched, the bending movement is triggered so that the tip moves away from the mechanical
stimulus (Images courtesy of A. Sadeghi and C. Lucarotti)

provides feedback to the external control system that drives the ER valve, which
then controls the ER fluid-based bending.
The tactile sensors were developed to mimic the tactile sensitivity of the root.
The sensors are normal force soft sensors, which can adapt and conform to the 3D
structure of the root. Upon an external force, a change in the capacitance is induced
by the decreased dielectric layer between two opposite electrodes. The building
materials were elastomers for the dielectric layer and conductive textiles for the
electrodes. The sensitivity can be optimized based on a balance between the
electrode area and dielectric thickness as well as a balance between the electrical