Untethered capsules are capable of entering the gastrointestinal (GI) tract and collecting fluid samples containing microbial communities from specific locations, facilitating the study of chronic diseases. However, existing sampling capsules are designed for single-site sampling, making it challenging to gather samples from multiple targets. This paper reports a magnetic-driven capsule for multiple sampling within the GI tract and an on-demand magnetic-triggered fluid sampling strategy. The capsule consists of a body, a magnetic-triggered negative pressure unit, and a reservoir unit. Composed of an elastic membrane and Magnet I, the negative pressure unit controls pressure change inside the capsule cavity on demand to pump the sample by switching the magnetic field, while the embedded Magnet I also enables real-time magnetic localization for regional targeting and position tracking. The reservoir unit integrates three sampling papers for fluid absorption, two waterproof layers that maintain contamination levels below 25% to ensure reliable multi-site sampling, and a rotating arm embedded with Magnet II for posture adjustment of the sampling paper. The pumping and storage performance of the capsule was systematically evaluated and optimized. Meanwhile, the capsule, actuated by an external magnetic field, was evaluated for its active locomotion performance. Finally, the feasibility of using the capsule to perform active navigation and multi-target sampling in a porcine intestine was validated viaex vivoexperiments.

Biological machines that use biological cells and soft materials in combination to obtain a sense of the environment driven by bioenergy and generate driving force are called biohybrid actuators. With the development of tissue engineering and organoid technology, researchers have applied biohybrid actuators technology to the research of precision medicine and targeted drug delivery, but the research on feedback and evaluation of biohybrid actuation performance is limited to visual and simulation calculations. Therefore, we hope to develop an intelligent crawling skeleton for sensing function, which can be used to evaluate the actuation ability of muscle actuators, and eventually realize the high-precision control of biohybrid actuators. In this work, an intelligent crawling skeleton based on three-dimensional liquid metal is proposed to detect and feedback the crawling of C2C12 muscle actuators. Three-dimensional muscle tissue was composed of mixing hydrogels and cells, and the functionalization of muscle rings was promoted using static mechanical forces and external electric field stimulation. The composite crawling skeleton is fabricated by inverting mold and soft lithography technology. The skeleton can adapt to large deformations above 90 degrees and is more sensitive to deformations by adjusting materials with different elastic modulus. Inspired by the tendon-bone structure, the intelligent crawling skeleton can obtain the deformation degree of the biohybrid actuator in the crawling process according to the characteristics of the deformation from the muscle tissue, and put forward a good idea for the feedback and closed-loop control of the biohybrid actuators.

This study describes a microfluidics experiment with ready classroom applications, designed to enhance students' understanding of fluid dynamics, controlled mixing, and bubble formation. The materials employed are safe and readily accessible, such as vinegar and baking soda, combined with PDMS microfluidic chips and a high-resolution microscope, to provide real-time observation of gas-liquid interactions. A syringe pump delivers the reactants into a micro-channel through which the fluid flow behavior and bubble formation can be visualized and quantified.(/p)The focus of the experiment is on elucidating the effects of different soda concentrations on bubble generation in a controlled laminar flow. The results show a nonlinear trend between soda concentration and bubble features: lower concentrations produce fewer but larger bubbles, moderate concentrations produce small bubbles more frequently. At 0.2 M, the average bubble area was approximately 389 μm2, and at 0.4 M, there were smaller bubbles but more frequent occurrences. As concentrations increased above 0.6 M, bubbles became more uniform in size and more circular.Flow rates were varied from 3 to 15 μL/min to assess bubble behavior. Most bubbles functioned as wall bubbles in the micro-channel and were not perfectly spherical because of the influence of the local flow field and concentration gradients. The size distribution and circularity of the bubbles were measured using image analysis tools developed in Python.This affordable and visually appealing platform provides an alternative hands-on experience for students to learn the fundamental principles of microfluidics, thereby connecting classroom concepts with real-world observations. The lab activity promotes data analysis, hypothesis testing, and deepening understanding of concepts—skills essential for both academic and applied research.

This work presents a flexible and effective micromixer based on optoelectronic tweezers (OET), which leverages both asymmetric induced-charge electro-osmosis (ICEO) and dielectrophoresis (DEP) phenomena on microscale anisotropic NdFeB particles. The asymmetric ICEO phenomenon is generated by symmetry breaking in the induced charge distributions of geometrically anisotropic NdFeB particles under AC electric field polarization. The DEP forces exerted on NdFeB particles are induced by the light-generated non-uniform electric field. Under the combined action of hydrodynamic forces from asymmetric ICEO vortices and positive DEP forces, NdFeB particles can be attracted into light-induced "virtual" electrodes and precisely track along light-defined trajectories. Experimental results demonstrate that the maximum motion speed of the NdFeB particles exceeds 300 μm/s, with the motion speed exhibiting a positive correlation with the applied voltage. Dynamically controlled virtual electrodes enable accurate capture and relocation of microparticles to arbitrary target positions. The stirring and mixing capability of the NdFeB particles is demonstrated by driving yeast cell motion.

Tactile information is the research hotspot of wearable flexible sensors due to its importance and complexity. With the innovation of wearable technology and robotics in healthcare, researchers are increasingly integrating wearable flexible sensors on the front end of robots to reproduce the hand tactile manipulation of human tissues. Therefore, it is hoped to develop a thin-film sensor that can be deployed in a small area to assist robots in surgery and data collection of human tissues. Here we use a one-step injection method to fabricate a novel composite sensor based on liquid metal. By laminating multiple PDMS microfluidic layers, the two parameters of pressure and deformation are measured simultaneously in a decoupled manner. The sensor is small and thin, making it easy to integrate into fingers/robot fingers for assistance. The finger/robot finger exerts pressure on the sensor and the sensor deforms with the material to identify the hardness of the material being touched. Separate performance tests of the two sensors show that the strain and pressure functions are decoupled from each other, and their ratios can identify and classify the hardness of different touched materials (glass, PDMS and silicone). This novel composite sensor we proposed can assist robots in manipulating human tissues during medical surgeries. At the same time, its function in tactile information feedback also has broad applications in medical treatment, rehabilitation and services.

This article reports an automated optically-induced dielectrophoresis (ODEP) system for characterizing the specific membrane capacitance (SMC) of individual cells. The simulation of cell motion is conducted to analyze the electrokinetic forces acting on the cell. A self-developed visual tracking algorithm for multicells is used to realize an automated process for determining the frequency-sweeping range, crossover frequencies, and cell radii. The SMC values of malignant bladder cancer cells (T24 and RT4) and normal urothelial cells (SV-HUC-1) were quantified using the automated system, demonstrating that the system has a measurement speed of ~1 cell/s, an accuracy of 1 kHz for the crossover frequency determination, and an accuracy of 0.2 μm for the cell radius measurement.

3D assembly of cellular structures is important for the fabrication of biological substitute in tissue engineering. In this paper, a novel rail-guided multi-microrobotic system was proposed for the assembly of cellular structure. The cellular 2-dimensional (2D) module was fabricated by UV illumination of the crosslinkable hydrogel. The coordinated manipulation among the micromanipulators was performed with newly designed concentric movement along the rail, which realized the arbitrary change of micromanipulator posture. Through the rotation of the end-effectors around the specimen without swapping out the visual field, the manipulation flexibility was improved. The distance information between the micromanipulator and the module was acquired from vision feedback system and utilized for the automatic pick-up of the microstructure. Through the cooperation among multi-manipulators with hybrid motors, the micromanipulation to assemble the 3D structure with 30 nm operation resolution was achieved. Finally, the rail-guided DeSCom system realized the bottom-up fabrication of cellular vascular-like microtube with vision feedback.

Microfluidic devices provide efficient approaches for building cellular tubular structures for in vitro tissue models in tissue engineering. In this paper, we report a novel method of constructing three-dimensional (3D) multilayered tubular structures based on axis translation of two-dimensionally (2D) microstructures inside microfluidic devices. The on-chip fabrication of movable 2D microstructures embedding fibroblasts (NIH/3T3) based on Poly (ethylene glycol) Diacrylate (PEGDA) was reported. Novel two-layered microfluidic devices were fabricated by Polydimethylsiloxane (PDMS), for conducting the fluidic self-assembly of the 2D microstructures. The self-assembly process was experimentally demonstrated. For improving the assembly results, a funneled structure and 3 micro grooves were added inside the microfluidic channel. Improved self-assembly result of constructing a multilayered tubular microstructure with higher efficiency was demonstrated.

Cellular vascular-like microtubes occupy an important position in tissue engineering for building in vitro tissue models. In this paper, we report a method of constructing three-dimensional (3D) multilayered vascular-like microtubes based on fluidic axis-translation self-assembly of two-dimensional (2D) microstructures inside microfluidic devices. The on-chip fabrication of cell (fibroblasts NIH/3T3) embedded 2D microstructures based on Poly (ethylene glycol) Diacrylate (PEGDA) and biodegradable material Gelatin Methacrylate (GelMa) were reported. A multilayered Polydimethylsiloxane (PDMS) microfluidic device was fabricated for conducting the fluidic self-assembly of 2D microstructures. The fluidic axis-translation self-assembly process was experimentally demonstrated. Multiple hydrogels embedded microtube was constructed. The fabrication of GelMa microstructures was demonstrated. The degradability of cell embedded GelMa microstructures was evaluated by long-term observation, and it shows the great potential of GelMa to be used for constructing cellular vascular-like microtubes.

3D tailor-made biodegradable scaffold integrated with biological cells or molecules is of great importance for tissue engineering. This paper addresses an improved method for exploring magnetic tweezers in patterning and aligning magnetic hydrogel fiber to fabricate large-scale engineered cell-hydrogel constructs. Magnetic hydrogel fibers were fabricated based on microfluidic device. The fabricated hydrogel fiber is made of alginic acid sodium and with a diameter of 34 μm. Magnetic nanoparticles is added into the alginic acid sodium solution to append magnetic material inside the fibers. The magnetic material inside the hydrogel fiber is regulated by the microfluidic device. Magnetic tweezers system based on solenoid electromagnet is utilized to evaluate the magnetic response of the magnetic hydrogel fiber. Evaluation results show the hydrogel fiber can be maneuvered by the proposed system with a positioning resolution of sub-micro level. The cultivation results of hydrogel fiber with C2C12 cells shows the potential for real applications of the proposed method in tissue engineering.

Recently the research about constructing 3 dimensional cell structures is very important for its great potential applications in tissue engineering. In this paper, we report a novel method of constructing multi-layered microstructures embedding cells via microfluidic devices. The on-chip fabrication of movable microstructures embedding fibroblasts (NIH/3T3) based on Poly (ethylene glycol) Diacrylate (PEGDA) was reported. Two approaches for assembling these movable microstructures were presented. One was a manual assembly method based on micromanipulation system and the other one was a self-assembly method based on microfluidic channel. Several manual assembly ways were demonstrated and a tube-shaped microstructure with 17 layers was assembled by an efficient assembly method. A novel microfluidic channel was presented for conducting self-assembly method and a 2-layered experimental microfluidic device was fabricated by Polydimethylsiloxane (PDMS). The self-assembly process of fabricated microstructures via this device was preliminarily demonstrated.

In this paper, an automatic system for single cell analysis inside an environmental scanning electron microscopy (ESEM) was proposed. Single yeast cell was put on an tungsten probe substrate inside ESEM. The endeffector for single cell analysis was fixed to an nanorobotic manipulator, which has three degrees of freedom, i.e. X, Y and Z translation. The real time images during the experiment can be observed by ESEM system in realtime. Therefore, the position of the endeffector and the single cell can be recognized by imaging processing. These position information were used as the feedback signal to control the movement of the nanorobotic manipulator. Finally, a single cell cutting experiment was performed to demonstrate the working mechanism of this system. Two types of cell pattern substrates were also designed and fabricated as the cell analysis chips for the automation single cell analysis in the future.

Constructing different patterns of cells and immobilizing these cells inside certain structures are very important issues for artificial tissue engineering. In this paper, we present methods of forming line pattern of yeast cells by dielectrophoresis (DEP) and immobilizing patterned cells by photo-crosslinkable resin. High speed cell pattering by DEP and on-chip fabrication of microstructure which contains patterned yeast cells is demonstrated. In order to applying DEP force for forming cell pattern, several novel microelectrodes are fabricated by Indium Tin Oxides (ITO) which are coated on the glass. The two kinds of DEP responses of yeast cell (W303) and the precise experimental parameters of them are confirmed. Based on negative DEP phenomenon, cell traps generated by microelectrode are demonstrated. Position control and transportation of yeast cells is performed by using cell traps. Besides, a cell trap matrix is fabricated and high speed cell pattering is performed. The experimental results show that the cell line patterns which contain hundreds of yeast cells can be formed by DEP within 1 second. The on-chip fabrication for arbitrary shapes of microstructures based on Poly Ethylene Glycol Diacrylate (PEG-DA) is reported. With the cell patterning by DEP and immobilizing by on-chip fabrication, microstructure which contains 3 lines of yeast cells is fabricated in the microfluidic channel, inside PEG-DA and NaCl solution.

For tissue engineering, it is very important to construct cell patterns and immobilize patterned cells inside certain structures. In this paper, we present methods of forming cell pattern by dielectrophoresis (DEP) and immobilizing cells by photo-crosslinkable resin inside microfluidic chips. High speed cell manipulation, including patterning and concentration control by DEP is demonstrated. Movable microstructure embedding cells is on-chip fabricated. Several microelectrodes are fabricated by Indium Tin Oxides (ITO) and Cr/Au. The two kinds of DEP responses of yeast cell (W303) and other particles are experimentally confirmed. Based on negative DEP phenomenon, line and circle patterns of cells and microbeads are high speed performed. Cell manipulation for patterning is completed within 1 second. The on-chip fabrication of movable microstructures embedding cells based on Poly Ethylene Glycol Diacrylate (PEG-DA) is reported. The microfluidic chip with separated patterning and fabrication areas is fabricated. With the cell concentration control by DEP and on-chip fabrication method, movable microstructures embedding microbeads of which the concentration is controllable are fabricated in the microfluidic channel, inside PEG-DA and NaCl solution.

The on-chip fabrication and manipulation of microstructures are expected to be applied for single cell analysis system such as cell manipulation and measurement tools. In this paper, we previously present a methodology for fabricating and assembling microstructures inside a microfluidic channel. By the illumination of patterned UV-ray through the mask under a microscope, microstructures with arbitrary shape are made of the photo-crosslinkable resin inside microfluidic device. The microstructures are fabricated at the desired place inside microfluidic channel and manipulated by optical tweezers. Based on the technique which can manipulate multiple points simultaneously by high-speed scanning of a single laser with galvanometer mirror, a rotational microstructure made of a microgear and a rotation axis is assembled and rotated. We also report two methods of solution replacement inside microfluidic channel which reduces viscosity of solvent in order to improve manipulation performance. By adjusting the concentration of photo-crosslinkable resin and replacing solution components, the viscosity of solvent inside channel can be changed. The manipulation speed of the rotational microstructure increases when the viscosity of solvent decreases, because the viscosity resistance for the movement of microstructure is weaker inside lower viscosity solvent. We fabricate rotational microstructures inside lower viscosity solvent and evaluate the movement efficiency compared with microstructures inside former high viscosity solvent.