The technology has the potential to revolutionise the way in which high-value fruits are sorted today
A team of researchers at the Indian Institute of Technology (IIT) Jodhpur has created and demonstrated a cost-effective and highly sensitive tactile pressure sensor for detecting fruit ripeness. The sensor utilises nanoneedle textured PDMS (polydimethylsiloxane) as the dielectric layer and is lithography-free, allowing for flexible and large-scale fabrication. The team characterised the sensitivity and hysterics response of the capacitive tactile sensor and examined its transient response.
By measuring the elastic modulus and capacitance, the researchers were able to demonstrate ripeness assessment for different types of tomatoes.
In horticulture, monitoring fruit ripeness is essential to maintain their freshness and quality. Various microsensors have been developed for fruit sorting and ripeness detection. For instance, some devices rely on chemical analysis of sugar and starch content, while others use electrochemical sensing, image processing, electronics noise, and tactile sensing methods. However, chemical analysis is destructive and not applicable at all stages of ripeness, while electrochemical sensing requires expensive equipment. Image processing for ripeness detection is limited to specific fruit families, and changes in colour are not reliable indicators of ripeness for some fruits such as kiwis, mangoes, and blueberries.
On the other hand, measuring firmness has been a dependable and automated method for assessing ripeness. Therefore, there is a need for a sensitive tactile sensor integrated into a robotic system, capable of providing pressure, mechanical stiffness, and firmness information for a sufficiently large number of fruits during harvesting and transportation.
The developed sensor is capable of sorting fruits as per their ripeness and hence, by integrating the newly developed sensor with a robotic arm, it will be possible to create a high-throughput system that can effectively sort fruits based on their ripeness and quality during the plucking or transportation stages. This cost-effective system will be particularly useful for exporting high-value fruits over long distances.