Self-Cleaning Surfaces Realized by Biologically Sized Magnetic Artificial Cilia

Magnetic artificial cilia (MAC) are small actuators inspired by biological cilia found in nature. In microfluidic chips, MAC can generate flow and remove microparticles, with applications in anti-fouling. However, the MAC used for anti-fouling in the current literature has dimensions of several hundred micrometers in length, which limits the application to relatively large length scales. Here, biologically-sized magnetic artificial cilia (b-MAC) which are only 45 micrometers long and that are randomly distributed on the surface, are used to remove microparticles. It is shown that microparticles with sizes ranging from 5 to 40 µm can be removed efficiently and the final cleanness ranges from 69% to 100%, with the highest cleanness for the highest actuation frequency applied (40 Hz). The lowest cleanness is obtained for microparticles with a size equal to the average pitch between the b-MAC. The randomness in cilia distribution appears to have a positive effect on cleanliness, compared with the authors’ earlier work using a regular cilia array. The demonstrated self-cleaning by the b-MAC constitutes an essential step toward efficient self-cleaning surfaces for real-life application in miniaturized microfluidic devices, such as lab-on-a-chip or organ-on-a-chip devices, as well as for preventing fouling of submerged surfaces such as marine sensors.</p

Self-Cleaning Surfaces Realized by Biologically Sized Magnetic Artificial Cilia

Magnetic artificial cilia (MAC) are small actuators inspired by biological cilia found in nature. In microfluidic chips, MAC can generate flow and remove microparticles, with applications in anti-fouling. However, the MAC used for anti-fouling in the current literature has dimensions of several hundred micrometers in length, which limits the application to relatively large length scales. Here, biologically-sized magnetic artificial cilia (b-MAC) which are only 45 micrometers long and that are randomly distributed on the surface, are used to remove microparticles. It is shown that microparticles with sizes ranging from 5 to 40 µm can be removed efficiently and the final cleanness ranges from 69% to 100%, with the highest cleanness for the highest actuation frequency applied (40 Hz). The lowest cleanness is obtained for microparticles with a size equal to the average pitch between the b-MAC. The randomness in cilia distribution appears to have a positive effect on cleanliness, compared with the authors’ earlier work using a regular cilia array. The demonstrated self-cleaning by the b-MAC constitutes an essential step toward efficient self-cleaning surfaces for real-life application in miniaturized microfluidic devices, such as lab-on-a-chip or organ-on-a-chip devices, as well as for preventing fouling of submerged surfaces such as marine sensors.</p

A high throughput array microscope for the mechanical characterization of biomaterials

In the last decade, the emergence of high throughput screening has enabled the development of novel drug therapies and elucidated many complex cellular processes. Concurrently, the mechanobiology community has developed tools and methods to show that the dysregulation of biophysical properties and the biochemical mechanisms controlling those properties contribute significantly to many human diseases. Despite these advances, a complete understanding of the connection between biomechanics and disease will require advances in instrumentation that enable parallelized, high throughput assays capable of probing complex signaling pathways, studying biology in physiologically relevant conditions, and capturing specimen and mechanical heterogeneity. Traditional biophysical instruments are unable to meet this need. To address the challenge of large-scale, parallelized biophysical measurements, we have developed an automated array high-throughput microscope system that utilizes passive microbead diffusion to characterize mechanical properties of biomaterials. The instrument is capable of acquiring data on twelve-channels simultaneously, where each channel in the system can independently drive two-channel fluorescence imaging at up to 50 frames per second. We employ this system to measure the concentration-dependent apparent viscosity of hyaluronan, an essential polymer found in connective tissue and whose expression has been implicated in cancer progression

Micro-elastometry on whole blood clots using actuated surface-attached posts (ASAPs)

We used magnetically actuatable micro-post arrays to measure blood clot elasticity for blood clotting diagnostics

Nanoparticle Diffusion Measures Bulk Clot Permeability

A clot's function is to achieve hemostasis by resisting fluid flow. Permeability is the measurement of a clot's hemostatic potential. It is sensitive to a wide range of biochemical parameters and pathologies. In this work, we consider the hydrodynamic phenomenon that reduces the mobility of fluid near the fiber surfaces. This no-slip boundary condition both defines the gel's permeability and suppresses nanoparticle diffusion in gel interstices. Here we report that, unlike previous work where steric effects also hindered diffusion, our system—nanoparticles in fibrin gel—was subject exclusively to hydrodynamic diffusion suppression. This result enabled an automated, high-throughput permeability assay that used small clot volumes. Permeability was derived from nanoparticle diffusion using the effective medium theory, and showed one-to-one correlation with measured permeability. This technique measured permeability without quantifying gel structure, and may therefore prove useful for characterizing similar materials (e.g., extracellular matrix) where structure is uncontrolled during polymerization and difficult to measure subsequently. We also report that PEGylation reduced, but did not eliminate, the population of immobile particles. We studied the forces required to pull stuck PEG particles free to confirm that the attachment is a result of neither covalent nor strong electrostatic binding, and discuss the relevance of this force scale to particle transport through physiological clots

A high throughput array microscope for the mechanical characterization of biomaterials

In the last decade, the emergence of high throughput screening has enabled the development of novel drug therapies and elucidated many complex cellular processes. Concurrently, the mechanobiology community has developed tools and methods to show that the dysregulation of biophysical properties and the biochemical mechanisms controlling those properties contribute significantly to many human diseases. Despite these advances, a complete understanding of the connection between biomechanics and disease will require advances in instrumentation that enable parallelized, high throughput assays capable of probing complex signaling pathways, studying biology in physiologically relevant conditions, and capturing specimen and mechanical heterogeneity. Traditional biophysical instruments are unable to meet this need. To address the challenge of large-scale, parallelized biophysical measurements, we have developed an automated array high-throughput microscope system that utilizes passive microbead diffusion to characterize mechanical properties of biomaterials. The instrument is capable of acquiring data on twelve-channels simultaneously, where each channel in the system can independently drive two-channel fluorescence imaging at up to 50 frames per second. We employ this system to measure the concentration-dependent apparent viscosity of hyaluronan, an essential polymer found in connective tissue and whose expression has been implicated in cancer progression

High throughput system for magnetic manipulation of cells, polymers, and biomaterials

In the past decade, high throughput screening (HTS) has changed the way biochemical assays are performed, but manipulation and mechanical measurement of micro- and nanoscale systems have not benefited from this trend. Techniques using microbeads (particles ∼0.1–10 μm) show promise for enabling high throughput mechanical measurements of microscopic systems. We demonstrate instrumentation to magnetically drive microbeads in a biocompatible, multiwell magnetic force system. It is based on commercial HTS standards and is scalable to 96 wells. Cells can be cultured in this magnetic high throughput system (MHTS). The MHTS can apply independently controlled forces to 16 specimen wells. Force calibrations demonstrate forces in excess of 1 nN, predicted force saturation as a function of pole material, and powerlaw dependence of F∼r−2.7±0.1. We employ this system to measure the stiffness of SR2+ Drosophila cells. MHTS technology is a key step toward a high throughput screening system for micro- and nanoscale biophysical experiments

Source data for the publication: Self-Cleaning Surfaces Realized by Biologically Sized Magnetic Artificial Cilia

This data set contains the source data of the publication: Cui, Z., Zhang, S., Wang, Y., Tormey, L., Kanies, O.S., Spero, R.C., Fisher, J.K. &amp; Toonder, J.M.J. den (2021). Self-cleaning surfaces realized by biologically sized magnetic artificial cilia. Adv. Mater. Interfaces 2021, 2102016. https://doi.org/10.1002/admi.202102016. In this study, biologically-sized magnetic artificial cilia (b-MAC) which are only 45 micrometers long and that are randomly distributed on the surface, are used to remove microparticles. The data are experimentally obtained with methods described in the publication