Effects of heat transfer and the membrane thermal conductivity on the thermally nanofluidic salinity gradient energy conversion

3D-Printed Wearable Electrochemical Energy Devices

Bio‐hybrid technologies aim to replicate the unique capabilities of biological systems that could surpass advanced artificial technologies. Soft bio‐hybrid robots consist of synthetic and living materials and have the potential to self‐assemble, regenerate, work autonomously, and interact safely with other species and the environment. Cells require a sufficient exchange of nutrients and gases, which is guaranteed by convection and diffusive transport through liquid media. The functional development and long‐term survival of biological tissues in vitro can be improved by dynamic flow culture, but only microfluidic flow control can develop tissue with fine structuring and regulation at the microscale. Full control of tissue growth at the microscale will eventually lead to functional macroscale constructs, which are needed as the biological component of soft bio‐hybrid technologies. This review summarizes recent progress in microfluidic techniques to engineer biological tissues, focusing on the use of muscle cells for robotic bio‐actuation. Moreover, the instances in which bio‐actuation technologies greatly benefit from fusion with microfluidics are highlighted, which include: the microfabrication of matrices, biomimicry of cell microenvironments, tissue maturation, perfusion, and vascularization.

https://onlinelibrary.wiley.com/doi/pdfdirect/10.1002/adma.202108427

Microfluidic Tissue Engineering and Bio‐Actuation

We study herein numerically the use of induced-charge electrokinetic phenomena to enable a flexible control of ion transport of dilute electrolyte in a straight ion concentration polarization system. The effect of three convection modes of induced-charge electrokinetic phenomena, including induced-charge electroosmosis, flow-field effect transistor, and alternating-current electroosmosis (ACEO), on convective arrestment of diffusive wave-front propagation is investigated by developing a cross-scale and fully coupled transient numerical simulation model, wherein multiple frequency electrochemical polarization and nonlinear diffuse charge dynamics in spatiotemporally varying solution conductivity are taken into account. We demonstrate by detailed comparative simulation studies that ACEO vortex flow field above a metal strip array arranged along the anodic chamber's bottom surface serves as the most efficient way for adjusting the salt density distribution at micrometer and even millimeter dimension, due to its high flexibility in controlling the stirring flow state with the introduction of two extra electrical parameters. The specific operating status is determined by whether the electrode array is floating in potential (induced-charge electroosmosis) or biased to ground (flow-field effect transistor) or forced to oscillate at another Fourier mode (ACEO). These results prove useful for on-chip electric current control with electroconvective stirring.

On ion transport regulation with field-effect nonlinear electroosmosis control in microfluidics embedding an ion-selective medium.

Dielectrophoresis (DEP) as a label-free cell separation approach in microdevices has been extensively investigated for a variety of applications. 3D microelectrodes made of conducting-PDMS inherit the merit of volumetric electrodes for generating influential DEP force throughout the entire channel depth and meanwhile, exploit low-cost fabrication process by soft lithography. However, the configuration of conducting-PDMS electrodes is limited to being embedded in sidewall of flow chamber, which leads to rather low flow rate and difficulties in extension of the flow rate. We previously reported a more effective configuration with 3D interdigitated electrodes made of silicon that assist cell sliding along solid tracks, yet such device requires expensive silicon dry etching and, moreover, the track appears to be patterned with non-straight and wavy outline, which not only hinders the flow rate but also allows cell sliding to occur only along its downstream side. Here we demonstrate low-cost silver-PDMS electrode-track featuring ideally straight outline that induces rather uniform drag to drive smooth cell sliding. Such design achieves live and dead cell separation at flow rate twice as that of silicon tracks with cell loading concentration 10 times higher. It also fully utilizes the track to enable cell sliding on both of the up- and down-stream sides. Notably, we also demonstrate that this track is expandable to be V-shape for more advanced bidirectional cell sliding, which is showcased here by tumor cells separation from lymphocytes at 1.2 mL/h. Such results greatly enhance the throughput as compared to the state-of-art conducting-PDMS based cell separator.

/pdf/high-throughput-dielectrophoretic-cell-sorting-assisted-by-2k3t60pb1i.pdf

High-throughput dielectrophoretic cell sorting assisted by cell sliding on scalable electrode tracks made of conducting-PDMS

RFID has been widely used for activity and gesture recognition in emerging interaction paradigms given its low cost, lightweight, and pervasiveness. However, current learning-based approaches on RFID sensing require significant efforts in data collection, feature extraction, and model training. To save data processing effort, we present MicroFluID, a novel RFID artifact based on a multiple-chip structure and microfluidic switches, which informs the input state by directly reading variable ID information instead of retrieving primitive signals. Fabricated on flexible substrates, four types of microfluidic switch circuits are designed to respond to external physical events, including pressure, bend, temperature, and gravity. By default, chips are disconnected into the circuit owing to the reserved gaps in transmission line. While external input or status change occurs, conductive liquid floating in the microfluidics channels will fill the gap(s), creating a connection to certain chip(s). In prototyping the device, we conducted a series of simulations and experiments to explore the feasibility of the multi-chip tag design, key fabrication parameters, interaction performance, and users' perceptions.

MicroFluID

RFID has been widely used for activity and gesture recognition in emerging interaction paradigms given its low cost, lightweight, and pervasiveness. However, current learning-based approaches on RFID sensing require significant efforts in data collection, feature extraction, and model training. To save data processing effort, we present MicroFluID, a novel RFID artifact based on a multiple-chip structure and microfluidic switches, which informs the input state by directly reading variable ID information instead of retrieving primitive signals. Fabricated on flexible substrates, four types of microfluidic switch circuits are designed to respond to external physical events, including pressure, bend, temperature, and gravity. By default, chips are disconnected into the circuit owing to the reserved gaps in transmission line. While external input or status change occurs, conductive liquid floating in the microfluidics channels will fill the gap(s), creating a connection to certain chip(s). In prototyping the device, we conducted a series of simulations and experiments to explore the feasibility of the multi-chip tag design, key fabrication parameters, interaction performance, and users' perceptions. 

Simon Zhan

Papers

MicroFluID

MicroFluID: A Multi-Chip RFID Tag for Interaction Sensing Based on Microfluidic Switches