Researchers have developed a soft robotic gripper that can inspect fruit for ripeness and harvest it without causing damage, a capability that could help reduce food waste and improve harvesting efficiency.
The device uses soft silicone and polyurethane fingers equipped with multiple sensors to measure a fruit’s size, shape, color and firmness before deciding whether it is ready to be picked. The system was tested on strawberries and can remove the fruit by twisting its stem rather than cutting it.
The gripper was developed by a team that includes Anand Mishra, assistant professor in the Department of Mechanical, Materials and Aerospace Engineering at West Virginia University. The research began at Cornell University and is continuing at WVU.
The technology addresses a major challenge in agriculture: harvesting delicate fruits at the right stage of ripeness. Fruits such as strawberries and raspberries have a narrow harvest window and can bruise easily during picking, transportation and storage.
Gentle grip, smart sensing
“Our gripper’s quick, accurate inspections and harvesting can reduce spoilage of fruits and lower supply chain costs,” Mishra said.
“Fruit inspections are critical for harvesting decisions that have traditionally been made by human workers. However, using human workers for harvesting involves challenges such as labor shortages, health concerns and inaccuracies in picking.”
Agricultural robots have been proposed as a solution, but many existing systems are designed for controlled greenhouse environments rather than outdoor farms. Traditional robotic grippers can also damage soft fruit because of their rigid structures.
The new system combines tactile and visual sensing in a soft robotic design. Stretchable optical fibers embedded inside each finger act as tactile and curvature sensors, while a miniature camera and distance sensor are mounted in the palm.
The five-fingered gripper can identify a fruit’s shape, stiffness and ripeness while also detecting slippage during handling. Researchers reported that the device can open and close in less than two seconds, lift loads weighing up to one kilogram and achieve nearly 100 percent accuracy in shape prediction.
According to the team, the technology could be particularly useful for fruits that do not show obvious visual signs of ripeness. Avocados are one example, where growers often rely on touch rather than appearance to determine harvest timing.
Beyond the orchard
“My research group at WVU is called the Robiotics Lab because we focus on robots that mimic biology,” Mishra said.
“We design squishy, squeezy, rubbery robots inspired by animals.”
The gripper’s design draws inspiration from biological systems and resembles both a human hand and a starfish. Researchers say the soft structure allows it to absorb forces differently than conventional rigid robots, making it better suited for handling delicate objects.
Beyond agriculture, the sensing technology could find use in other fields that require careful manipulation.
“This system offers applications in space exploration, health care, food handling and underwater manipulation,” Mishra said.
“In biomedical robotics, for instance, the integration of curvature and tactile sensing could enhance wearable and rehabilitation devices.”
Researchers believe the combination of soft materials and integrated sensing could help robots interact more safely and effectively with both objects and their surroundings.
The study was published in the journal Nature Communications.