Wenfeng Wan

Vision-based Nano Robotic System for High-throughput Non-embedded Cell Cutting

Cell cutting is a significant task in biology study, but the highly productive non-embedded cell cutting is still a big challenge for current techniques. This paper proposes a vision-based nano robotic system and then realizes automatic non-embedded cell cutting with this system. First, the nano robotic system is developed and integrated with a nanoknife inside an environmental scanning electron microscopy (ESEM). Then, the positions of the nanoknife and the single cell are recognized, and the distance between them is calculated dynamically based on image processing. To guarantee the positioning accuracy and the working efficiency, we propose a distance-regulated speed adapting strategy, in which the moving speed is adjusted intelligently based on the distance between the nanoknife and the target cell. The results indicate that the automatic non-embedded cutting is able to be achieved within 1–2 mins with low invasion benefiting from the high precise nanorobot system and the sharp edge of nanoknife. This research paves a way for the high-throughput cell cutting at cell’s natural condition, which is expected to make significant impact on the biology studies, especially for the in-situ analysis at cellular and subcellular scale, such as cell interaction investigation, neural signal transduction and low invasive cell surgery.

Multidirectional Image Sensing for Microscopy Based on a Rotatable Robot

Image sensing at a small scale is essentially important in many fields, including microsample observation, defect inspection, material characterization and so on. However, nowadays, multi-directional micro object imaging is still very challenging due to the limited field of view (FOV) of microscopes. This paper reports a novel approach for multi-directional image sensing in microscopes by developing a rotatable robot. First, a robot with endless rotation ability is designed and integrated with the microscope. Then, the micro object is aligned to the rotation axis of the robot automatically based on the proposed forward-backward alignment strategy. After that, multi-directional images of the sample can be obtained by rotating the robot within one revolution under the microscope. To demonstrate the versatility of this approach, we view various types of micro samples from multiple directions in both optical microscopy and scanning electron microscopy, and panoramic images of the samples are processed as well. The proposed method paves a new way for the microscopy image sensing, and we believe it could have significant impact in many fields, especially for sample detection, manipulation and characterization at a small scale.

Controllable 3D alginate hydrogel patterning via visible-light induced electrodeposition

The fabrication of alginate hydrogel in 3D has recently received increasing attention owing to its distinct efficacy as biocompatible scaffold for 3D cell culture, biomedical and tissue engineering. We report a controllable 3D alginate hydrogel patterning method by developing a visible-light induced electrodeposition chip. The chip mainly consists of a photoconductive titanyl phthalocyanine (TiOPc) anode plate, an indium tin oxide (ITO) cathode plate and the mixed solution (1% sodium alginate and 0.25% CaCO3 nano particles) between them. After a designed visible-light pattern is projected onto the TiOPc plate, the produced H(+) by electrolysis will trigger Ca(2+) near the anode (illuminated area), and then the gelation of calcium alginate patterns, as desired, happens controllably. In addition, we further establish an exponential model to elucidate the gel growth v.s. time and current density. The results indicate that the proposed method is able to fabricate various 3D alginate hydrogel patterns in a well controllable manner, and maintain the laden cells at high survival rate (>98% right after gel formation). This research paves an alternative way for 3D alginate hydrogel patterning with high controllability and productivity, which would benefit the research in biomedical and tissue engineering.

Automatic Sample Alignment Under Microscopy for 360° Imaging Based on the Nanorobotic Manipulation System

Microscopy has been an indispensable tool for micro/nanosample imaging, manipulation, and characterization. However, viewing the micro/nanosample from multidirection is still a big challenge for current microscopy. To address the above issue, this paper proposes a novel nanorobotic manipulation system for the automatic alignment and multidirectional imaging under microscopes. First, a miniature rotation robot with three degrees of freedom is designed and integrated with a microscope. Then, a forward-backward alignment strategy containing three loops, i.e., position shift loop, angle loop, and magnification loop, is proposed to align the sample to the rotation axis of the robot automatically. After that, the sample is imaged from multidirection by rotating the robot with one revolution (360°). Finally, the alignment accuracy is evaluated and multi-directional images of various samples are implemented. This study provides a new way for the microscopic imaging, which is expected to exert a significant impact in multiple fields on a small scale, including microscopy imaging, microdefect detection, micromanipulation, in situ characterization, and so on.

Paper-Based Electrodeposition Chip for 3D Alginate Hydrogel Formation

Hydrogel has been regarded as one significant biomaterial in biomedical and tissue engineering due to its high biocompatibility. This paper proposes a novel method to pattern calcium alginate hydrogel in a 3D way via electrodeposition process based on a piece of paper. Firstly, one insulating paper with patterned holes is placed on one indium tin oxide (ITO) glass surface, which is put below another ITO glass. Then, 1% sodium alginate solution with 0.25% CaCO3 nano particles is filled between these two glasses. In the bottom glass, patterns of electrodes followed patterns of holes on the insulating layer. Hydrogel forms on patterned electrodes when electrochemical potential is applied due to electrodeposition. The experiments demonstrate that the pattern of alginate hydrogels follows the pattern of electrodes exactly. In addition, the hydrogel’s height is controllable by applied potential and reaction time. An equivalent circuit model and a hydrogel growth model have been built to predict the electrodeposition current and hydrogel’s growth. This method for gel formation is easy and cheap since the main material is one piece of insulated paper, which provides an easy and controllable method for 3D hydrogel patterning.

Multi-directional Characterization for Pollen Tubes Based on a Nanorobotic Manipulation System

Pollen tubes’ main function is to transport gametes to ovules. Mechanical properties of pollen tubes affect their growth and penetration. Most existing systems for characterizing pollen tubes can only characterize pollen tubes from one direction. However, considering pollen tubes’ nonuniform properties, results got from one fixed direction don’t necessarily represent pollen tubes’ overall properties. In order to characterize pollen tubes from multi-direction instead of one direction, a nanorobotic system is proposed herein. The system contains two robots, robot 1 for sample assembly and robot 2 for sensor assembly. Robot 1’s rotation degree enables pollen tubes to be characterized from multi-direction. During experiments, the pollen tube is bent at different angles from 0° to 360°. Bending forces at different angle are quite different. The results demonstrate that pollen tubes are inhomogeneous along circumferential direction and justify the necessity to characterize pollen tubes from multi-direction. Experiment results can be used to measure pollen tubes’ stiffness at different direction and analyze how pollen tubes penetrate through pistil.

Three-dimensional calcium alginate hydrogel patterning by using TiOPc-based controllable electrodeposition

We report a feasible light-addressable electrodepostion approach to realize rapidly controllable fabrication of 3D hydrogel structure on an organic photoconductive material electrode surface. The fabrication process is carried out by using an optical system setup. A pattern produced by a visible-light projection system is projected onto the titanium oxide phthalocyanine (TiOPc) coated chip as a virtual electrode and a DC electric felid is applied between the ITO glass and the TiOPc chip. The DC electric fields trigger the sodium alginate cross-link with the calcium ions (Ca2+) to form the 3D caalginate hydrogel in situ on the top of the TiOPc electrode surface simply. This study provides flexible and controllable 3D gel structure fabrication method, which would facilitate the research of drug testing and tissue engineering.

3D cell assembly via anode electrode manipulation

Cell culture is a basic and significant task in biological engineering. Many cell culture works have been studied up to now. However, the cell is always cultured in a 2D plate in current techniques. Thus, the cells can only growth on a flat plate, which condition is far from that in vivo. Hydrogel is a kind of biocompatible material, inside with the cell can spread and growth. It provides us a method to study the cells property in real 3D environment. Thus, how to control the shape of the gel is an important topic. In this paper, we proposed a method to control the gels shape and position based on the manipulation of the anode electrode. The gel generation is based on the electrodeposition of calcium alginate. The reaction speed is controlled by the applied current. Three examples were demonstrated to show how our system is working. The result shows that straight gel line, arbitrary gel shape on substrate and multi-layer gel structure can be obtained by this proposed method.