Modelling tomato pericarp microstructure as force control reference for harvesting robot.

BACKGROUND: The harvest of fruit can be significantly advanced with the thriving development of intelligent and automated robot technologies. Nevertheless, the picking success rate of tomato fruit still requires improvement as some fruits are unexpectedly damaged inside, which is imperceptible by machine vision. Herein, a modelling method based on modified Voronoi algorithm is proposed to reconstruct the cellular structure of tomato pericarp. RESULTS: Based on the reconstructed micro-model, the compression physical behaviour of the pericarp cells is simulated to observe internal local stress and potential damage. It is revealed that the simulation result for pericarps of tomatoes with different ripeness is highly consistent to the experimental tests, which has well validated the feasibility of this modelling and simulation method. CONCLUSION: A Voronoi-based modelling method is proposed for micro-reconstruction of tomato pericarp, and the corresponding compression simulation results agree well with the experimental tests. Such result can be utilized as reference to improve the grasping force control for harvesting robot to avoid invisible damage induced by accident overload issue. With the predicting result, superior success rate can be achieved to enhance robot performance. © 2024 Society of Chemical Industry.

Reconstruction of plant microstructure using distance weighted tessellation algorithm optimized by virtual segmentation.

The accurate reconstruction model of plant microstructure is important for obtaining the mechanical properties of plant tissues. In this paper, a virtual segmentation technique is proposed to optimize Delaunay triangulation. Based on the optimized Delaunay triangulation, an Optimized Distance Weighted Tessellation (ODWT) algorithm is developed. Two different structures, namely carrot and retting maize vascular bundles, were reconstructed via the ODWT algorithm. The accuracy of ODWT is evaluated statistically by comparing with Centroid-based Voronoi Tessellation (CVT) and Area Weighted Tessellation (AWT). The results show that ODWT has distinct advantages over CVT and AWT. It is worth mentioning that ODWT has better performance than CVT when there exists large diversity in adjacent cell area. It is found that CVT and AWT fail to reconstruct cells with elongated and concave shapes, while ODWT shows excellent feasibility and reliability. Furthermore, ODWT is capable of establishing finite tissue boundary, which CVT and AWT have failed to realize. The purpose of this work is to develop an algorithm with higher accuracy to implement the preprocessing for further numerical study of plants properties. The comparison results of the simulated values of the longitudinal tensile modulus with the experimental value show that ODWT algorithm can improve the prediction accuracy of multi-scale models on mechanical properties.

A new PEGDA/CNF aerogel-wet hydrogel scaffold fabricated by a two-step method.

The scaffold is one of the most important components in tissue engineering. There are a lot of natural or synthetic materials applied for the fabrication of scaffolds. Among them, cellulose nanofibril (CNF) is an important natural polymer with characteristics of superior biocompatibility, notable nanostructure effect and excellent hydrophilia, which make it qualified for serving as a raw material of scaffolds. In this paper, polyethylene glycol diacrylate (PEGDA) was mixed with CNF at different content ratios, which were 0%, 0.35%, 0.7%, 1.05% and 1.4% (m/v). Furthermore, the visible light photoinitiator (eosin Y + TEA + NVP) was first added to this mixture solution to form a new kind of bio-resin. A two-step method including stereolithography and freeze-drying is put forward to fabricate a new aerogel-wet hydrogel scaffold. Scaffolds were fabricated by using a self-built stereolithography platform and the mechanical properties, printability and biocompatibility of the hydrogel scaffolds were investigated thoroughly. The original hydrogel scaffold was fabricated through stereolithography, where CNFs were applied to regulate the mechanical properties of the hydrogel and the printability of the bio-resin. After the freeze-drying process, the original hydrogel was transformed into the aerogel-wet hydrogel whose compressive modulus is reduced by 20%. Furthermore, the surface structure of the hydrogel scaffold is modified to provide a better environment for adhesion and growth of BMSc.

An effective DLP 3D printing strategy of high strength and toughness cellulose hydrogel towards strain sensing.

Photocurable 3D printing technology has outperformed extrusion-based 3D printing technology in material adaptability, resolution, and printing rate, yet is still limited by the insecure preparation and selection of photoinitiators and thus less reported. In this work, we developed a printable hydrogel that can effectively facilitate various solid or hollow structures and even lattice structures. The chemical and physical dual-crosslinking strategy combined with cellulose nanofibers (CNF) significantly improved the strength and toughness of photocurable 3D printed hydrogels. In this study, the tensile breaking strength, Young's modulus, and toughness of poly(acrylamide-co-acrylic acid)D/cellulose nanofiber (PAM-co-PAA)D/CNF hydrogels were 375 %, 203 % and 544 % higher than those of the traditional single chemical crosslinked (PAM-co-PAA)S hydrogels, respectively. Notably, its outstanding compressive elasticity enabled it to recover under 90 % strain compression (about 4.12 MPa). Resultantly, the proposed hydrogel can be utilized as a flexible strain sensor to monitor the motions of human movements, such as the bending of fingers, wrists, and arms, and even the vibration of a speaking throat. The output of electrical signals can still be collected through strain even under the condition of energy shortage. In addition, photocurable 3D printing technology can provide customized services for hydrogel-based e-skin, such as hydrogel-based bracelets, fingerstall, and finger joint sleeves.