Pineapple harvesting is a key step in pineapple field production. At present, pineapple fruits are usually picked manually. With decreasing labor resources and increasing production costs, machines have been used instead of manual picking approaches in the modern pineapple industry. This paper briefly describes the basic situation of pineapple planting worldwide. Based on the degree of automation of mechanized pineapple harvesting equipment, the main structural forms, core technologies, and operation modes of semi-automatic, automatic, and intelligent pineapple harvesting equipment are summarized. The research status and existing problems of key pineapple fruit picking robots, such as fruit recognition, maturity classification, positioning, and separation of pineapple fruits, are analyzed. Considering the problems of pineapple harvesting equipment, such as difficulty entering the ground, low harvesting efficiency, low picking success rate, and fruit damage, innovative future research directions for mechanized pineapple harvesting technology are proposed, such as combining agricultural machinery and agronomical principles, integrating mechanized, automated, and intelligent technology, and developing modular designs and generalized approaches.

Orientation adjustment of the micro-component is the key but most difficult part of micro-assembly. In this paper, the mechanism and physical process for orientation adjustment of micro-components absorbed by a liquid-drop micromanipulator are analyzed. The transformation relationship between the orientation of micro-components and the shape of the liquid-drop micromanipulator tip is studied. The quantitative mapping relationship between the shape of the liquid-drop micromanipulator tip and the orientation of micro components is established. A method to quantitatively control the tilt and rotation of micro-components is presented, and the feasibility of the method is verified by experiment. The results show that the orientation of a micro-component absorbed by a liquid-drop micromanipulator varies with the orientation of the micromanipulator. Quantitative control of the orientation of the micro-component can be realized by changing the shape of micromanipulator tip by controlling the upward and downward movement of tungsten rods.

A novel release method of micro-objects based on the liquid bridge configuration is proposed. A mathematical model of the liquid bridge is established to analyse the influence of the liquid bridge meniscus configuration on the liquid bridge force. Moreover, the release method and the physical process of the micro-object are discussed and the feasibility of the method is verified by simulation and experiment. The research and experimental results show that the liquid bridge configuration, which can be controlled by the liquid volume and the height of the liquid bridge, can adjust the liquid bridge force to realize the release of micro-objects.

A method of manipulating particles based on swirl was proposed in this article. The pressure and velocity distributions of swirling flow field were analyzed theoretically. The mechanism of particle trapping and controlling based on swirling flow was discussed, and the feasibility of the proposed method was verified by experiments. The results show that a swirling flow can be generated by placing two microtubules in parallel and jetting fluid in opposite directions. Particles with arbitrary size and shape can be trapped and controlled to rotate and move directionally and quantitatively with proper swirling flow parameters.

This paper proposes a microfluidic system for particle manipulation, which is comprised of a microfluidic chip, a driving device, a manipulation dish, and associated accessories. The microfluidic chip integrates a swirl structure with three microchannels, allowing for trapping, rotating, transporting, pairing, and enriching particles with different parameters by controlling the jet velocity of each microchannel. The driving device is mainly constructed with three push–pull syringe pumps to ensure the stability of the swirl flow field during manipulation. Experimental results demonstrate that the developed microfluidic system can achieve multifunctional and long-term (hours) particle manipulation.

A particle manipulation method was presented in this paper based on opposed jets. In such a method, particles were trapped near the stagnation point of the flow field and moved by controlling the position of the stagnation point. The hold direction of the flow to the particle was changed by changing the orientation of the opposed-jet flow field where a particle is trapped. Subsequently, the directional and quantitative movement of the particle in any direction was achieved. Taking micron particles as examples, we analyzed the control mechanism of particles based on opposed jets and evaluated the influence of jet velocity, inner diameter, distance of end face, radial error, and position of capillaries on the particle control performance by simulations. The feasibility of the proposed method was proved by a great number of experiments, and the results demonstrated that particles with the arbitrary size and shape can be trapped and moved directionally and quantitatively by constructing an opposed-jet flow field. The trapping and position control of particles can be manipulated without any contact with proper flow field parameters.