Correction: Direct laser writing-enabled 3D printing strategies for microfluidic applications.

Correction for 'Direct laser writing-enabled 3D printing strategies for microfluidic applications' by Olivia M. Young , , 2024, DOI: https://doi.org/10.

Direct laser writing-enabled 3D printing strategies for microfluidic applications.

Over the past decade, additive manufacturing-or "three-dimensional (3D) printing"-has attracted increasing attention in the community as a pathway to achieve sophisticated system architectures that are difficult or infeasible to fabricate conventional means. One particularly promising 3D manufacturing technology is "direct laser writing (DLW)", which leverages two-photon (or multi-photon) polymerization (2PP) phenomena to enable high geometric versatility, print speeds, and precision at length scales down to the 100 nm range. Although researchers have demonstrated the potential of using DLW for microfluidic applications ranging from organ on a chip and drug delivery to micro/nanoparticle processing and soft microrobotics, such scenarios present unique challenges for DLW.

FABRICATION OF MULTILUMEN MICROFLUIDIC TUBING FOR DIRECT LASER WRITING.

Among the numerous additive manufacturing or "three-dimensional (3D) printing" techniques, two-photon Direct Laser Writing (DLW) is distinctively suited for applications that demand high geometric versatility with micron-to-submicron-scale feature resolutions. Recently, " DLW (DLW)" has emerged as a powerful approach for printing 3D microfluidic structures directly atop meso/macroscale fluidic tubing that can be manipulated by hand; however, difficulties in creating custom DLW-compatible multilumen tubing at such scales has hindered progress. To address this impediment, here we introduce a novel methodology for fabricating submillimeter multilumen tubing for DLW 3D printing.

TOWARD CONTROLLED-RELEASE DRUG DELIVERY MICROCARRIERS ENABLED BY DIRECT LASER WRITING 3D PRINTING.

Controlled-release, and especially long-acting, drug delivery systems hold promise for improving treatments for numerous medical conditions. Previously, we reported an additive manufacturing or "three-dimensional (3D) printing" approach for fabricating liquid-core-shell-cap microcarriers comprising standard photoresists. Here we explore the potential to extend this strategy to achieve microcarriers comprising biodegradable materials as a new pathway to controlled-release drug delivery options.

A 3D-MICROPRINTED COAXIAL NOZZLE FOR FABRICATING LONG, FLEXIBLE MICROFLUIDIC TUBING.

A variety of emerging applications, particularly those in medical and soft robotics fields, are predicated on the ability to fabricate long, flexible meso/microfluidic tubing with high customization. To address this need, here we present a hybrid additive manufacturing (or "three-dimensional (3D) printing") strategy that involves three key steps: () using the "Vat Photopolymerization (VPP) technique, "Liquid-Crystal Display (LCD)" 3D printing to print a bulk microfluidic device with three inlets and three concentric outlets; () using "Two-Photon Direct Laser Writing (DLW)" to 3D microprint a coaxial nozzle directly atop the concentric outlets of the bulk microdevice, and then () extruding paraffin oil and a liquid-phase photocurable resin through the coaxial nozzle and into a polydimethylsiloxane (PDMS) channel for UV exposure, ultimately producing the desired tubing. In addition to fabricating the resulting tubing-composed of polymerized photomaterial-at arbitrary lengths (.

Physics-Informed Modeling and Control of Multi-Actuator Soft Catheter Robots.

Catheter-based endovascular interventional procedures have become increasingly popular in recent years as they are less invasive and patients spend less time in the hospital with less recovery time and less pain. These advantages have led to a significant growth in the number of procedures that are performed annually. However, it is still challenging to position a catheter in a target vessel branch within the highly complicated and delicate vascular structure.

Deterministic Lateral Displacement Using Hexagonally Arranged, Bottom-Up-Inspired Micropost Arrays.

Size-based separation of particles in microfluidic devices can be achieved using arrays of micro- or nanoscale posts using a technique known as deterministic lateral displacement (DLD). To date, DLD arrays have been limited to parallelogram or rotated-square arrangements of posts, with various post shapes having been explored in these two principal arrangements. This work examines a new DLD geometry based on patterning obtainable through self-assembly of single-layer nanospheres, which we call hexagonally arranged triangle (HAT) geometry.

Bayesian Optimization for Design of Multi-Actuator Soft Catheter Robots.

Catheter-based diagnosis and therapy have grown increasingly in recent years due to their improved clinical outcomes including decreased morbidity, shorter recovery time and minimally invasiveness compared to open surgeries. Although the scalability, customizability, and diversity of soft catheter robots are widely recognized, designers and roboticists still lack comprehensive techniques for modeling and designing them. This difficulty arises due to their continuum nature, which makes characterizing the properties and predicting a soft catheter's behavior challenging, complicating robot design tasks.

Fully 3D-printed soft robots with integrated fluidic circuitry.

The emergence of soft robots has presented new challenges associated with controlling the underlying fluidics of such systems. Here, we introduce a strategy for additively manufacturing unified soft robots comprising fully integrated fluidic circuitry in a single print run via PolyJet three-dimensional (3D) printing. We explore the efficacy of this approach for soft robots designed to leverage novel 3D fluidic circuit elements-e.

3D printed vascular phantoms for high-resolution biophotonic image quality assessment via direct laser writing.

Fluorescence imaging techniques such as fluorescein angiography and fundus autofluorescence are often used to diagnose retinal pathologies; however, there are currently no standardized test methods for evaluating device performance. Here we present microstructured fluorescent phantoms fabricated using a submicron-scale three-dimensional printing technology, direct laser writing (DLW). We employ an in situ DLW technique to print 10 µm diameter microfluidic channels that support perfusions of fluorescent dyes.

3D microfluidics via cyclic olefin polymer-based in situ direct laser writing.

In situ direct laser writing (isDLW) strategies that facilitate the printing of three-dimensional (3D) nanostructured components directly inside of, and fully sealed to, enclosed microchannels are uniquely suited for manufacturing geometrically complex microfluidic technologies. Recent efforts have demonstrated the benefits of using micromolding and bonding protocols for isDLW; however, the reliance on polydimethylsiloxane (PDMS) leads to limited fluidic sealing (e.g.

A facile multi-material direct laser writing strategy.

Direct laser writing (DLW) is a three-dimensional (3D) manufacturing technology that offers vast architectural control at submicron scales, yet remains limited in cases that demand microstructures comprising more than one material. Here we present an accessible microfluidic multi-material DLW (μFMM-DLW) strategy that enables 3D nanostructured components to be printed with average material registration accuracies of 100 ± 70 nm (ΔX) and 190 ± 170 nm (ΔY) - a significant improvement versus conventional multi-material DLW methods. Results for printing 3D microstructures with up to five materials suggest that μFMM-DLW can be utilized in applications that demand geometrically complex, multi-material microsystems, such as for photonics, meta-materials, and 3D cell biology.

3-D printed photoreceptor phantoms for evaluating lateral resolution of adaptive optics imaging systems.

With adaptive optics (AO), optical coherence tomography and scanning laser ophthalmoscopy imaging systems can resolve individual photoreceptor cells in living eyes, due to enhanced lateral spatial resolution. However, no standard test method exists for experimentally quantifying this parameter in ophthalmic AO imagers. Here, we present three-dimensional (3-D) printed phantoms, which enable the measurement of lateral resolution in an anatomically relevant manner.

Geometric Determinants of In-Situ Direct Laser Writing.

Direct laser writing (DLW) is a three-dimensional (3D) manufacturing technology that offers significant geometric versatility at submicron length scales. Although these characteristics hold promise for fields including organ modeling and microfluidic processing, difficulties associated with facilitating the macro-to-micro interfaces required for fluid delivery have limited the utility of DLW for such applications. To overcome this issue, here we report an in-situ DLW (isDLW) strategy for creating 3D nanostructured features directly inside of-and notably, fully sealed to-sol-gel-coated elastomeric microchannels.

A Role for 3D Printing in Kidney-on-a-Chip Platforms.

The advancement of "kidney-on-a-chip" platforms - submillimeter-scale fluidic systems designed to recapitulate renal functions in vitro - directly impacts a wide range of biomedical fields, including drug screening, cell and tissue engineering, toxicity testing, and disease modelling. To fabricate kidney-on-a-chip technologies, researchers have primarily adapted traditional micromachining techniques that are rooted in the integrated circuit industry; hence the term, "chip." A significant challenge, however, is that such methods are inherently monolithic, which limits one's ability to accurately recreate the geometric and architectural complexity of the kidney in vivo.

Finger-powered microfluidic systems using multilayer soft lithography and injection molding processes.

Point-of-care (POC) and disposable biomedical applications demand low-power microfluidic systems with pumping components that provide controlled pressure sources. Unfortunately, external pumps have hindered the implementation of such microfluidic systems due to limitations associated with portability and power requirements. Here, we propose and demonstrate a 'finger-powered' integrated pumping system as a modular element to provide pressure head for a variety of advanced microfluidic applications, including finger-powered on-chip microdroplet generation.

Microfluidic bead-based diodes with targeted circular microchannels for low Reynolds number applications.

Self-regulating fluidic components are critical to the advancement of microfluidic processors for chemical and biological applications, such as sample preparation on chip, point-of-care molecular diagnostics, and implantable drug delivery devices. Although researchers have developed a wide range of components to enable flow rectification in fluidic systems, engineering microfluidic diodes that function at the low Reynolds number (Re) flows and smaller scales of emerging micro/nanofluidic platforms has remained a considerable challenge. Recently, researchers have demonstrated microfluidic diodes that utilize high numbers of suspended microbeads as dynamic resistive elements; however, using spherical particles to block fluid flow through rectangular microchannels is inherently limited.

Dual-mode hydrodynamic railing and arraying of microparticles for multi-stage signal detection in continuous flow biochemical microprocessors.

Continuous flow particulate-based microfluidic processors are in critical demand for emerging applications in chemistry and biology, such as point-of-care molecular diagnostics. Challenges remain, however, for accomplishing biochemical assays in which microparticle immobilization is desired or required during intermediate stages of fluidic reaction processes. Here we present a dual-mode microfluidic reactor that functions autonomously under continuous flow conditions to: (i) execute multi-stage particulate-based fluidic mixing routines, and (ii) array select numbers of microparticles during each reaction stage (e.

Hydrodynamic resettability for a microfluidic particulate-based arraying system.

Precision hydrodynamic controls of microparticles (e.g., microbeads and cells) are critical to diverse lab-on-a-chip applications.

Continuous flow multi-stage microfluidic reactors via hydrodynamic microparticle railing.

"Multi-stage" fluidic reactions are integral to diverse biochemical assays; however, such processes typically require laborious and time-intensive fluidic mixing procedures in which distinct reagents and/or washes must be loaded sequentially and separately (i.e., one-at-a-time).