3D printed microfluidic devices: enablers and barriers

Extraction of small molecule from human plasma by prototyping 3D printed sorbent through extruded filament for LC-MS/MS analysis

Analytical sample preparation techniques are regarded as crucial steps for analyzing compounds from different biological matrices. The development of new extraction techniques is a modern trend in the bioanalytical sciences. 3D printed techniques have emerged as a valuable technology for prototyping devices in customized shapes for a cost-effective way to advance analytical sample preparation techniques. The present study aims to fabricate customized filaments through the hot-melt extrusion (HME) technique followed by fused deposition modeling mediated 3D printing process for rapid prototyping of 3D printed sorbents to extract a sample from human plasma. Thus, we fabricated our own indigenous filament using poly (vinyl alcohol), Eudragit® RSPO, and tri-ethyl citrate through HME to prototype the fabricated filament into a 3D printed sorbent for the extraction of small molecules. The 3D sorbent was applied to extract hydrocortisone from human plasma and analyzed using a validated LC-MS/MS method. The extraction procedure was optimized, and the parameters influencing the sorbent extraction were systematically investigated. The extraction recovery of hydrocortisone was found to be >82% at low, medium, and high quality control samples, with a relative standard deviation of <2%. The intra-and inter-day precisions for hydrocortisone ranged from 1.0% to 12% and 2.0%-10.0%, respectively, whereas the intra-and inter-day accuracy for hydrocortisone ranged from 93.0% to 111.0% and 92.0% to 110.0%, respectively. The newly customizable size and shape of the 3D printed sorbent opens new possibilities for extracting small molecules from human plasma.

Determination of total protein content in biomedical products by the PDMS-assisted lab-in-a-syringe assay using 3D printed scaffolds removal

The aim of our work was to develop a low-cost, portable device for the fast and easy determination of total protein content by using PDMS-based lab-in-a-syringe technology with removal of 3D-printed channels. We proposed two designs with a one-step PDMS curing and a two-step PDMS-curing fabrication procedure. The one-step PDMS microdevices were found to be the best in the view of preparation, repeatability, and stability of the reagent. This design was then applied for the determination of total protein content in biomedical products using the Bradford assay.

Recapitulation of First Pass Metabolism Using 3D Printed Microfluidic Chip and Organoid

The low bioavailability of oral drugs due to first pass metabolism is a major obstacle in drug development. With significant developments in the field of in vitro organ modeling and microfluidic chip three-dimensional (3D) printing, the challenge is to apply these for the production and evaluation of new drug candidates. This study aimed to produce a microfluidic chip to recapitulate and assess the feasibility of the first pass metabolism. The infill condition of the polycarbonate transparent filament and layer height was optimized to visualize and maintain the organoid or spheroid on the chip. Next, the chip was fabricated using a 3D printer after a computer-aided design (CAD). The chip consisted of three wells of different heights. The small intestinal (SI) organoid and colorectal adenocarcinoma spheroids were placed on the second and third wells, respectively. No additional equipment was assembled, and the tilted tunnel was connected to each well to transport the material by gradient force. The chip was fabricated using 50% and 0.1 um thickness. Among the three different prototypes of chip (chips 1, 2, and 3), the highest distribution of plasmids in the Matrigel of the second well was observed in Chip 2 at 48 h. The effect of first pass metabolism was analyzed using docetaxel. In the chip without an SI organoid, there was a marked decrease in the viability of colorectal adenocarcinoma spheroids due to drug efficacy. However, in the chip with the SI organoid, no significant change in viability was observed because of first pass metabolism. In conclusion, we presented a simple, fast, and low-cost microfluidic chip to analyze the efficacy change of candidate drug by the first pass metabolism.

Micromixer with Fine-Tuned Mathematical Spiral Structures

Micromixers with the microchannel structure can enable rapid and efficient mixing of multiple types of fluids on a microfluidic chip. Herein, we report the mixing performance of three passive micromixers based on the different mathematical spiral structures. We study the fluid flow characteristics of Archimedes spiral, Fermat spiral, and hyperbolic spiral structures with various channel widths and Reynolds number (Re) ranging from 0 to 10 via numerical simulation and visualization experiments. In addition, we analyze the mechanism of streamlines and Dean vortices at different cross sections during fluid flows. As the fluid flows in the Fermat spiral channel, the centrifugal force induces the Dean vortex to form a chaotic advection, enhancing the fluid mixing performance. By integrating the Fermat spiral channel into a microfluidic chip, we successfully detect acute myocardial infarction (AMI) marker with the double-antibody sandwich method and reduce the detection time to 10 min. This method has a low reagent consumption and a high reaction efficiency and demonstrates great potential in point-of-care testing (POCT).

3D printing for the integration of porous materials into miniaturised fluidic devices: A review

Porous materials facilitate the efficient separation of chemicals and particulate matter by providing selectivity through structural and surface properties and are attractive as sorbent owing to their large surface area. This broad applicability of porous materials makes the integration of porous materials and microfluidic devices important in the development of more efficient, advanced separation platforms. Additive manufacturing approaches are fundamentally different to traditional manufacturing methods, providing unique opportunities in the fabrication of fluidic devices. The complementary 3D printing (3DP) methods are each accompanied by unique opportunities and limitations in terms of minimum channel size, scalability, functional integration and automation. This review focuses on the developments in the fabrication of 3DP miniaturised fluidic devices with integrated porous materials, focusing polymer-based methods including fused filament fabrication (FFF), inkjet 3D printing and digital light projection (DLP). The 3DP methods are compared based on resolution, scope for multimaterial printing and scalability for manufacturing. As opportunities for printing pores are limited by resolution, the focus is on approaches to incorporate materials with sub-micron pores to be used as membrane, sorbent or stationary phase in separation science using Post-Print, Print-Pause-Print and In-Print processes. Technical aspects analysing the efficiency of the fabrication process towards scalable manufacturing are combined with application aspects evaluating the separation and/or extraction performance. The review is concluded with an overview on achievements and opportunities for manufacturable 3D printed membrane/sorbent integrated fluidic devices.

Droplet-based microfluidics in biomedical applications

Droplet-based microfluidic systems have been employed to manipulate discrete fluid volumes with immiscible phases. Creating the fluid droplets at microscale has led to a paradigm shift in mixing, sorting, encapsulation, sensing, and designing high throughput devices for biomedical applications. Droplet microfluidics has opened many opportunities in microparticle synthesis, molecular detection, diagnostics, drug delivery, and cell biology. In the present review, we first introduce standard methods for droplet generation (i.e., passive and active methods) and discuss the latest examples of emulsification and particle synthesis approaches enabled by microfluidic platforms. Then, the applications of droplet-based microfluidics in different biomedical applications are detailed. Finally, a general overview of the latest trends along with the perspectives and future potentials in the field are provided.

Dynamic phase control with printing and fluidic materials' interaction by inkjet printing an RF sensor directly on a stereolithographic 3D printed microfluidic structure

Stereolithographic (SL) three-dimensional (3D) printing of microfluidic channels and inkjet printing of radio frequency (RF) electronics are promising lab-on-a-chip technologies. However, the effective integration of the two techniques has been challenging since the fabricated parts need to be combined via an additional bonding process, such as plasma bonding. This study proposes combining RF electronics with SL printed microfluidic structures by directly inkjet printing onto a 3D printed mould. This allows the inkjet printing of RF electronics with high conductivity (8 × 10⁶ S m^-1) and high resolution (50 μm) as a surface modification of the 3D printed mould. This process combines the three-dimensional printing of microfluidic parts and the inkjet printing of RF sensors into a single process. The proposed approach increases the interaction between a printed RF part and a fluid material by adjusting the distance between them, and it can be applied to various resins and 3D printing methods. Furthermore, the proposed fabrication process was applied to a dynamic phase advanced and delayed transmission line (TL) operating at 3.8 GHz as a fluidic sensor. Consequently, using the same pattern, a higher phase shift range per microliter of 10° was obtained than the 1° for conventional phase shift TLs.

Recent Advances in Microfluidic Platforms for Programming Cell-Based Living Materials

Cell-based living materials, including single cells, cell-laden fibers, cell sheets, organoids, and organs, have attracted intensive interests owing to their widespread applications in cancer therapy, regenerative medicine, drug development, and so on. Significant progress in materials, microfabrication, and cell biology have promoted the development of numerous promising microfluidic platforms for programming these cell-based living materials with a high-throughput, scalable, and efficient manner. In this review, the recent progress of novel microfluidic platforms for programming cell-based living materials is presented. First, the unique features, categories, and materials and related fabrication methods of microfluidic platforms are briefly introduced. From the viewpoint of the design principles of the microfluidic platforms, the recent significant advances of programming single cells, cell-laden fibers, cell sheets, organoids, and organs in turns are then highlighted. Last, by providing personal perspectives on challenges and future trends, this review aims to motivate researchers from the fields of materials and engineering to work together with biologists and physicians to promote the development of cell-based living materials for human healthcare-related applications.

Fused Deposition Modeling of Microfluidic Chips in Transparent Polystyrene

Polystyrene (PS) is one of the most commonly used thermoplastic materials worldwide and plays a ubiquitous role in today's biomedical and life science industry and research. The main advantage of PS lies in its facile processability, its excellent optical and mechanical properties, as well as its biocompatibility. However, PS is only rarely used in microfluidic prototyping, since the structuring of PS is mainly performed using industrial-scale replication processes. So far, microfluidic chips in PS have not been accessible to rapid prototyping via 3D printing. In this work, we present, for the first time, 3D printing of transparent PS using fused deposition modeling (FDM). We present FDM printing of transparent PS microfluidic channels with dimensions as small as 300 µm and a high transparency in the region of interest. Furthermore, we demonstrate the fabrication of functional chips such as Tesla-mixer and mixer cascades. Cell culture experiments showed a high cell viability during seven days of culturing, as well as enabling cell adhesion and proliferation. With the aid of this new PS prototyping method, the development of future biomedical microfluidic chips will be significantly accelerated, as it enables using PS from the early academic prototyping all the way to industrial-scale mass replication.

Complex 3D microfluidic architectures formed by mechanically guided compressive buckling

Microfluidic technologies have wide-ranging applications in chemical analysis systems, drug delivery platforms, and artificial vascular networks. This latter area is particularly relevant to 3D cell cultures, engineered tissues, and artificial organs, where volumetric capabilities in fluid distribution are essential. Existing schemes for fabricating 3D microfluidic structures are constrained in realizing desired layout designs, producing physiologically relevant microvascular structures, and/or integrating active electronic/optoelectronic/microelectromechanical components for sensing and actuation. This paper presents a guided assembly approach that bypasses these limitations to yield complex 3D microvascular structures from 2D precursors that exploit the full sophistication of 2D fabrication methods. The capabilities extend to feature sizes <5 μm, in extended arrays and with various embedded sensors and actuators, across wide ranges of overall dimensions, in a parallel, high-throughput process. Examples include 3D microvascular networks with sophisticated layouts, deterministically designed and constructed to expand the geometries and operating features of artificial vascular networks.

Advancing 3D-Printed Microfluidics: Characterization of a Gas-Permeable, High-Resolution PDMS Resin for Stereolithography

The rapid expansion of microfluidic applications in the last decade has been curtailed by slow, laborious microfabrication techniques. Recently, microfluidics has been explored with additive manufacturing (AM), as it has gained legitimacy for producing end-use products and 3D printers have improved resolution capabilities. While AM satisfies many shortcomings with current microfabrication techniques, there still lacks a suitable replacement for the most used material in microfluidic devices, poly(dimethylsiloxane) (PDMS). Formulation of a gas-permeable, high-resolution PDMS resin was developed using a methacrylate–PDMS copolymer and the novel combination of a photoabsorber, Sudan I, and photosensitizer, 2-Isopropylthioxanthone. Resin characterization and 3D printing were performed using a commercially available DLP–SLA system. A previously developed math model, mechanical testing, optical transmission, and gas-permeability testing were performed to validate the optimized resin formula. The resulting resin has Young’s modulus of 11.5 MPa, a 12% elongation at break, and optical transmission of >75% for wavelengths between 500 and 800 nm after polymerization, and is capable of creating channels as small as 60 µm in height and membranes as thin as 20 µm. The potential of AM is just being realized as a fabrication technique for microfluidics as developments in material science and 3D printing technologies continue to push the resolution capabilities of these systems.

Topographical Vacuum Sealing of 3D-Printed Multiplanar Microfluidic Structures

We demonstrate a novel way of creating three-dimensional microfluidic channels capable of following complex topographies. To this end, substrates with open channels and different geometries were 3D-printed, and the open channels were consecutively closed with a thermoplastic using a low-resolution vacuum-forming approach. This process allows the sealing of channels that are located on the surface of complex multiplanar topographies, as the thermoplastic aligns with the surface-shape (the macrostructure) of the substrate, while the microchannels remain mostly free of thermoplastic as their small channel size resists thermoplastic inflow. This new process was analyzed for its capability to consistently close different substrate geometries, which showed reliable sealing of angles >90°. Furthermore, the thermoplastic intrusion into channels of different widths was quantified, showing a linear effect of channel width and percentage of thermoplastic intrusion; ranging from 43.76% for large channels with 2 mm width to only 5.33% for channels with 500 µm channel width. The challenging sealing of substrate ‘valleys’, which are created when two large protrusions are adjacent to each other, was investigated and the correlation between protrusion distance and height is shown. Lastly, we present three application examples: a serpentine mixer with channels spun around a cuboid, increasing the usable surface area; a cuvette-inspired flow cell for a 2-MXP biosensor based on molecular imprinted polymers, fitting inside a standard UV/Vis-Spectrophotometer; and an adapter system that can be manufactured by one-sided injection molding and is self-sealed before usage. These examples demonstrate how this novel technology can be used to easily adapt microfluidic circuits for application in biosensor platforms.

Configurable 3D Printed Microfluidic Multiport Valves with Axial Compression

In the last decade, the fabrication of microfluidic chips was revolutionized by 3D printing. It is not only used for rapid prototyping of molds, but also for manufacturing of complex chips and even integrated active parts like pumps and valves, which are essential for many microfluidic applications. The manufacturing of multiport injection valves is of special interest for analytical microfluidic systems, as they can reduce the injection to detection dead volume and thus enhance the resolution and decrease the detection limit. Designs reported so far use radial compression of rotor and stator. However, commercially available nonprinted valves usually feature axial compression, as this allows for adjustable compression and the possibility to integrate additional sealing elements. In this paper, we transfer the axial approach to 3D-printed valves and compare two different printing techniques, as well as six different sealing configurations. The tightness of the system is evaluated with optical examination, weighing, and flow measurements. The developed system shows similar performance to commercial or other 3D-printed valves with no measurable leakage for the static case and leakages below 0.5% in the dynamic case, can be turned automatically with a stepper motor, is easy to scale up, and is transferable to other printing methods and materials without design changes.

Understanding and improving FDM 3D printing to fabricate high-resolution and optically transparent microfluidic devices

The fabrication of microfluidic devices through fused deposition modeling (FDM) 3D printing has faced several challenges, mainly regarding obtaining microchannels with suitable transparency and sizes. Thus, the use of this printing system to fabricate microdevices for analytical and bioanalytical applications is commonly limited when compared to other printing technologies. However, for the first time, this work shows a systematic study to improve the potential of FDM 3D printers for the fabrication of transparent microfluidic devices. Several parameters and printing characteristics were addressed in both theoretical and experimental ways. It was found that the geometry of the printer nozzle plays a significant role in the thermal radiation effect that limits the 3D printing resolution. This drawback was minimized by adapting an airbrush tip (0.2 mm orifice diameter) to a conventional printer nozzle. The influence of the height and width of the extruded layer on the resolution and transparency in 3D-printed microfluidic devices was also addressed. Following the adjustments proposed, microchannels were obtained with an average width of around 70 μm ± 11 μm and approximately 80% visible light transmission (for 640 μm thickness). Therefore, the reproducibility and resolution of FDM 3D printing could be improved, and this achievement can expand the capability of this printing technology for the development of microfluidic devices, particularly for analytical applications.

Spatially and optically tailored 3D printing for highly miniaturized and integrated microfluidics

Traditional 3D printing based on Digital Light Processing Stereolithography (DLP-SL) is unnecessarily limiting as applied to microfluidic device fabrication, especially for high-resolution features. This limitation is due primarily to inherent tradeoffs between layer thickness, exposure time, material strength, and optical penetration that can be impossible to satisfy for microfluidic features. We introduce a generalized 3D printing process that significantly expands the accessible spatially distributed optical dose parameter space to enable the fabrication of much higher resolution 3D components without increasing the resolution of the 3D printer. Here we demonstrate component miniaturization in conjunction with a high degree of integration, including 15 μm × 15 μm valves and a 2.2 mm × 1.1 mm 10-stage 2-fold serial diluter. These results illustrate our approach's promise to enable highly functional and compact microfluidic devices for a wide variety of biomolecular applications.

Engineered neural circuits for modeling brain physiology and neuropathology

The neural circuits of the central nervous system are the regulatory pathways for feeling, motion control, learning, and memory, and their dysfunction is closely related to various neurodegenerative diseases. Despite the growing demand for the unraveling of the physiology and functional connectivity of the neural circuits, their fundamental investigation is hampered because of the inability to access the components of neural circuits and the complex microenvironment. As an alternative approach, in vitro human neural circuits show principles of in vivo human neuronal circuit function. They allow access to the cellular compartment and permit real-time monitoring of neural circuits. In this review, we summarize recent advances in reconstituted in vitro neural circuits using engineering techniques. To this end, we provide an overview of the fabrication techniques and methods for stimulation and measurement of in vitro neural circuits. Subsequently, representative examples of in vitro neural circuits are reviewed with a particular focus on the recapitulation of structures and functions observed in vivo, and we summarize their application in the study of various brain diseases. We believe that the in vitro neural circuits can help neuroscience and the neuropharmacology. STATEMENT OF SIGNIFICANCE: Despite the growing demand to unravel the physiology and functional connectivity of the neural circuits, the studies on the in vivo neural circuits are frequently limited due to the poor accessibility. Furthermore, single neuron-based analysis has an inherent limitation in that it does not reflect the full spectrum of the neural circuit physiology. As an alternative approach, in vitro engineered neural circuit models have arisen because they can recapitulate the structural and functional characteristics of in vivo neural circuits. These in vitro neural circuits allow the mimicking of dysregulation of the neural circuits, including neurodegenerative diseases and traumatic brain injury. Emerging in vitro engineered neural circuits will provide a better understanding of the (patho-)physiology of neural circuits.

Fused filament fabrication 3D printed polylactic acid electroosmotic pumps

Additive manufacturing (3D printing) offers a flexible approach for the production of bespoke microfluidic structures such as the electroosmotic pump. Here a readily accessible fused filament fabrication (FFF) 3D printing technique has been employed for the first time to produce microcapillary structures using low cost thermoplastics in a scalable electroosmotic pump application. Capillary structures were formed using a negative space 3D printing approach to deposit longitudinal filament arrangements with polylactic acid (PLA) in either "face-centre cubic" or "body-centre cubic" arrangements, where the voids deliberately formed within the deposited structure act as functional micro-capillaries. These 3D printed capillary structures were shown to be capable of functioning as a simple electroosmotic pump (EOP), where the maximum flow rate of a single capillary EOP was up to 1.0 μl min^-1 at electric fields of up to 750 V cm^-1. Importantly, higher flow rates were readily achieved by printing parallel multiplexed capillary arrays.

3D printing of glass by additive manufacturing techniques: a review

Additive manufacturing (AM), which is also known as three-dimensional (3D) printing, uses computer-aided design to build objects layer by layer. Here, we focus on the recent progress in the development of techniques for 3D printing of glass, an important optoelectronic material, including fused deposition modeling, selective laser sintering/melting, stereolithography (SLA) and direct ink writing. We compare these 3D printing methods and analyze their benefits and problems for the manufacturing of functional glass objects. In addition, we discuss the technological principles of 3D glass printing and applications of 3D printed glass objects. This review is finalized by a summary of the current achievements and perspectives for the future development of the 3D glass printing technique.

Rapid Fabrication by Digital Light Processing 3D Printing of a SlipChip with Movable Ports for Local Delivery to Ex Vivo Organ Cultures

SlipChips are two-part microfluidic devices that can be reconfigured to change fluidic pathways for a wide range of functions, including tissue stimulation. Currently, fabrication of these devices at the prototype stage requires a skilled microfluidic technician, e.g., for wet etching or alignment steps. In most cases, SlipChip functionality requires an optically clear, smooth, and flat surface that is fluorophilic and hydrophobic. Here, we tested digital light processing (DLP) 3D printing, which is rapid, reproducible, and easily shared, as a solution for fabrication of SlipChips at the prototype stage. As a case study, we sought to fabricate a SlipChip intended for local delivery to live tissue slices through a movable microfluidic port. The device was comprised of two multi-layer components: an enclosed channel with a delivery port and a culture chamber for tissue slices with a permeable support. Once the design was optimized, we demonstrated its function by locally delivering a chemical probe to slices of hydrogel and to living tissue with up to 120 µm spatial resolution. By establishing the design principles for 3D printing of SlipChip devices, this work will enhance the ability to rapidly prototype such devices at mid-scale levels of production.

Microfabricated Devices for Confocal Microscopy on Biological Samples

Microfabricated devices have found applications in a range of biomedical research problems in recent years, with thousands of research papers published and multiple commercial devices now available. This chapter is intended to provide an overview of the available options for devices compatible with confocal microscopy, including an overview of fabrication techniques and some examples of device use. Although there are times when off-the-shelf devices are well suited for the problem at hand, in some cases customized devices are necessary or more convenient. Protocols for researchers who wish to make their own devices are outlined below; although fabricating templates for devices requires some specialized equipment, making PDMS or hydrogel devices from templates can be done in a standard laboratory setting.

Engineering mechanobiology through organoids-on-chip: A strategy to boost therapeutics

The mechanical environment of living cells is as critical as chemical signaling. Mechanical stimuli play a pivotal role in organogenesis and tissue homeostasis. Unbalances in mechanotransduction pathways often lead to diseases, such as cancer, cystic fibrosis, and neurodevelopmental disorders. Despite its inherent relevance, there is a lack of proper mechanoresponsive in vitro study systems. In this context, there is an urge to engineer innovative, robust, dynamic, and reliable organotypic technologies to better connect cellular processes to organ-level function and multi-tissue cross-talk. Mechanically active organoid-on-chip has the potential to surpass this challenge. These systems converge microfabrication, microfluidics, biophysics, and tissue engineering fields to emulate key features of living organisms, hence, reducing costs, time, and animal testing. In this review, we intended to present cutting-edge organ-on-chip platforms that integrate biomechanical stimuli as well as novel multicellular culture, such as organoids. We focused on its application in two main fields: precision medicine and drug development. Moreover, we also discussed the state of the art for the development of an engineered model to assess patient-derived tumor organoid metastatic potential. Finally, we highlighted the current drawbacks and emerging opportunities to match the industry needs. We envision the use of mechanoresponsive organotypic-on-chip microdevices as an indispensable tool for precision medicine, drug development, disease modeling, tissue engineering, and developmental biology.

Manufacturing of 3D-Printed Microfluidic Devices for the Synthesis of Drug-Loaded Liposomal Formulations

Microfluidic technique has emerged as a promising tool for the production of stable and monodispersed nanoparticles (NPs). In particular, this work focuses on liposome production by microfluidics and on factors involved in determining liposome characteristics. Traditional fabrication techniques for microfluidic devices suffer from several disadvantages, such as multistep processing and expensive facilities. Three-dimensional printing (3DP) has been revolutionary for microfluidic device production, boasting facile and low-cost fabrication. In this study, microfluidic devices with innovative micromixing patterns were developed using fused deposition modelling (FDM) and liquid crystal display (LCD) printers. To date, this work is the first to study liposome production using LCD-printed microfluidic devices. The current study deals with 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) liposomes with cholesterol (2:1) prepared using commercial and 3D-printed microfluidic devices. We evaluated the effect of microfluidic parameters, chip manufacturing, material, and channel design on liposomal formulation by analysing the size, PDI, and ζ-potential. Curcumin exhibits potent anticancer activity and it has been reported that curcumin-loaded liposomes formulated by microfluidics show enhanced encapsulation efficiency when compared with other reported systems. In this work, curcumal liposomes were produced using the developed microfluidic devices and particle sizing, ζ-potential, encapsulation efficiency, and in vitro release studies were performed at 37 °C.

Programmable DNA-Based Boolean Logic Microfluidic Processing Unit

As molecular computing materials, information-encoded deoxyribonucleic acid (DNA) strands provide a logical computing process by cascaded and parallel chain reactions. However, the reactions in DNA-based combinational logic computing are mostly achieved through a manual process by adding desired DNA molecules in a single microtube or a substrate. For DNA-based Boolean logic, using microfluidic chips can afford automated operation, programmable control, and seamless combinational logic operation, similar to electronic microprocessors. In this paper, we present a programmable DNA-based microfluidic processing unit (MPU) chip that can be controlled via a personal computer for performing DNA calculations. To fabricate this DNA-based MPU, polydimethylsiloxane was cast using double-sided molding techniques for alignment between the microfluidics and valve switch. For a uniform surface, molds fabricated using a three-dimensional printer were spin-coated by a polymer. For programming control, the valve switch arms were operated by servo motors. In the MPU controlled via a personal computer or smartphone application, the molecules with two input DNAs and a logic template DNA were reacted for the basic AND and OR operations. Furthermore, the DNA molecules reacted in a cascading manner for combinational AND and OR operations. Finally, we demonstrated a 2-to-1 multiplexer and the XOR operation with a three-step cascade reaction using the simple DNA-based MPU, which can perform Boolean logic operations (AND, OR, and NOT). Through logic combination, this DNA-based Boolean logic MPU, which can be operated using programming language, is expected to facilitate the development of complex functional circuits such as arithmetic logical units and neuromorphic circuits.

How 3D printing can boost advances in analytical and bioanalytical chemistry

3D printing fabrication methods have received lately an enormous attention by the scientific community. Laboratories and research groups working on analytical chemistry applications, among others, have advantageously adopted 3D printing to fabricate a wide range of tools, from common laboratory hardware to fluidic systems, sample treatment platforms, sensing structures, and complete fully functional analytical devices. This technology is becoming more affordable over time and therefore preferred over the commonly used fabrication processes like hot embossing, soft lithography, injection molding and micromilling. However, to better exploit 3D printing fabrication methods, it is important to fully understand their benefits and limitations which are also directly associated to the properties of the materials used for printing. Costs, printing resolution, chemical and biological compatibility of the materials, design complexity, robustness of the printed object, and integration with commercially available systems represent important aspects to be weighted in relation to the intended task. In this review, a useful introductory summary of the most commonly used 3D printing systems and mechanisms is provided before the description of the most recent trends of the use of 3D printing for analytical and bioanalytical chemistry. Concluding remarks will be also given together with a brief discussion of possible future directions.

3D printed microfluidic lab-on-a-chip device for fiber-based dual beam optical manipulation

3D printing of microfluidic lab-on-a-chip devices enables rapid prototyping of robust and complex structures. In this work, we designed and fabricated a 3D printed lab-on-a-chip device for fiber-based dual beam optical manipulation. The final 3D printed chip offers three key features, such as (1) an optimized fiber channel design for precise alignment of optical fibers, (2) an optically clear window to visualize the trapping region, and (3) a sample channel which facilitates hydrodynamic focusing of samples. A square zig–zag structure incorporated in the sample channel increases the number of particles at the trapping site and focuses the cells and particles during experiments when operating the chip at low Reynolds number. To evaluate the performance of the device for optical manipulation, we implemented on-chip, fiber-based optical trapping of different-sized microscopic particles and performed trap stiffness measurements. In addition, optical stretching of MCF-7 cells was successfully accomplished for the purpose of studying the effects of a cytochalasin metabolite, pyrichalasin H, on cell elasticity. We observed distinct changes in the deformability of single cells treated with pyrichalasin H compared to untreated cells. These results demonstrate that 3D printed microfluidic lab-on-a-chip devices offer a cost-effective and customizable platform for applications in optical manipulation.

Microfluidics for Drug Development: From Synthesis to Evaluation

Drug development is a long process whose main content includes drug synthesis, drug delivery, and drug evaluation. Compared with conventional drug development procedures, microfluidics has emerged as a revolutionary technology in that it offers a miniaturized and highly controllable environment for bio(chemical) reactions to take place. It is also compatible with analytical strategies to implement integrated and high-throughput screening and evaluations. In this review, we provide a comprehensive summary of the entire microfluidics-based drug development system, from drug synthesis to drug evaluation. The challenges in the current status and the prospects for future development are also discussed. We believe that this review will promote communications throughout diversified scientific and engineering communities that will continue contributing to this burgeoning field.

Biomedical Applications of Metal 3D Printing

Additive manufacturing's attributes include print customization, low per-unit cost for small- to mid-batch production, seamless interfacing with mainstream medical 3D imaging techniques, and feasibility to create free-form objects in materials that are biocompatible and biodegradable. Consequently, additive manufacturing is apposite for a wide range of biomedical applications including custom biocompatible implants that mimic the mechanical response of bone, biodegradable scaffolds with engineered degradation rate, medical surgical tools, and biomedical instrumentation. This review surveys the materials, 3D printing methods and technologies, and biomedical applications of metal 3D printing, providing a historical perspective while focusing on the state of the art. It then identifies a number of exciting directions of future growth: (a) the improvement of mainstream additive manufacturing methods and associated feedstock; (b) the exploration of mature, less utilized metal 3D printing techniques; (c) the optimization of additively manufactured load-bearing structures via artificial intelligence; and (d) the creation of monolithic, multimaterial, finely featured, multifunctional implants.

Roll-to-plate additive manufacturing

In this paper, we propose a roll-to-plate (R2P) projection micro-stereolithography (PSL) 3D printer, where layers of photopolymer are transferred and photopolymerized through a flexible membrane. Benefitting from the "coat-expose-peel" procedure, highly viscous material can be printed quickly with good vertical resolution. Most importantly, the multinozzle dispensing method enables the fabrication of multimaterial architectures with high throughput, low material consumption, and low cross-contamination. R2P-PSL exhibits superior features for flexible 3D printing in terms of material complexity. For this purpose, we envision infinite scenarios involving potential applications in bionics, biotechnology, microcircuit graphics, photonic devices, microfluidics and material science.

A 3D Printer Guide for the Development and Application of Electrochemical Cells and Devices

3D printing is a type of additive manufacturing (AM), a technology that is on the rise and works by building parts in three dimensions by the deposit of raw material layer upon layer. In this review, we explore the use of 3D printers to prototype electrochemical cells and devices for various applications within chemistry. Recent publications reporting the use of Fused Deposition Modelling (fused deposition modeling®) technique will be mostly covered, besides papers about the application of other different types of 3D printing, highlighting the advances in the technology for promising applications in the near future. Different from the previous reviews in the area that focused on 3D printing for electrochemical applications, this review also aims to disseminate the benefits of using 3D printers for research at different levels as well as to guide researchers who want to start using this technology in their research laboratories. Moreover, we show the different designs already explored by different research groups illustrating the myriad of possibilities enabled by 3D printing.

New Endeavors of (Micro)Tissue Engineering: Cells Tissues Organs on-Chip and Communication Thereof

The development of new therapies is tremendously hampered by the insufficient availability of human model systems suitable for preclinical research on disease target identification, drug efficacy, and toxicity. Thus, drug failures in clinical trials are too common and too costly. Animal models or standard 2D in vitro tissue cultures, regardless of whether they are human based, are regularly not representative of specific human responses. Approaching near human tissues and organs test systems is the key goal of organs-on-chips (OoC) technology. This technology is currently showing its potential to reduce both drug development costs and time-to-market, while critically lessening animal testing. OoC are based on human (stem) cells, potentially derived from healthy or disease-affected patients, thereby amenable to personalized therapy development. It is noteworthy that the OoC market potential goes beyond pharma, with the possibility to test cosmetics, food additives, or environmental contaminants. This (micro)tissue engineering-based technology is highly multidisciplinary, combining fields such as (developmental) biology, (bio)materials, microfluidics, sensors, and imaging. The enormous potential of OoC is currently facing an exciting new challenge: emulating cross-communication between tissues and organs, to simulate more complex systemic responses, such as in cancer, or restricted to confined environments, as occurs in osteoarthritis. This review describes key examples of multiorgan/tissue-on-chip approaches, or linked organs/tissues-on-chip, focusing on challenges and promising new avenues of this advanced model system. Additionally, major emphasis is given to the translation of established tissue engineering approaches, bottom up and top down, towards the development of more complex, robust, and representative (multi)organ/tissue-on-chip approaches.

Photoclick Chemistry: A Bright Idea

At its basic conceptualization, photoclick chemistry embodies a collection of click reactions that are performed via the application of light. The emergence of this concept has had diverse impact over a broad range of chemical and biological research due to the spatiotemporal control, high selectivity, and excellent product yields afforded by the combination of light and click chemistry. While the reactions designated as "photoclick" have many important features in common, each has its own particular combination of advantages and shortcomings. A more extensive realization of the potential of this chemistry requires a broader understanding of the physical and chemical characteristics of the specific reactions. This review discusses the features of the most frequently employed photoclick reactions reported in the literature: photomediated azide-alkyne cycloadditions, other 1,3-dipolarcycloadditions, Diels-Alder and inverse electron demand Diels-Alder additions, radical alternating addition chain transfer additions, and nucleophilic additions. Applications of these reactions in a variety of chemical syntheses, materials chemistry, and biological contexts are surveyed, with particular attention paid to the respective strengths and limitations of each reaction and how that reaction benefits from its combination with light. Finally, challenges to broader employment of these reactions are discussed, along with strategies and opportunities to mitigate such obstacles.

Selective Fluorination of the Surface of Polymeric Materials after Stereolithography 3D Printing

With the microfluidics community embracing 3D resin printing as a rapid fabrication method, controlling surface chemistry has emerged as a new challenge. Fluorination of 3D-printed surfaces is highly desirable in many applications due to chemical inertness, low friction coefficients, antifouling properties, and the potential for selective hydrophobic patterning. Despite sporadic reports, silanization methods have not been optimized for covalent bonding with polymeric resins. As a case study, we tested the silanization of a commercially available (meth)acrylate-based resin (BV-007A) with a fluoroalkyl trichlorosilane. Interestingly, plasma oxidation was unnecessary for silanization of this resin and indeed was ineffective. Solvent-based deposition in a fluorinated oil (FC-40) generated significantly higher contact angles than deposition in ethanol or gas-phase deposition, yielding hydrophobic surfaces with contact angle >110° under optimized conditions. Attenuated total reflectance-Fourier transform infrared spectroscopy indicated that the increase in the contact angle correlated with consumption of a carbonyl moiety, suggesting covalent bonding of silane without plasma oxidation. Consistent with a covalent bond, silanization was resistant to mechanical damage and hydrolysis in methanol and was stable over long-term storage. When tested on a suite of photocrosslinkable resins, this silanization protocol generated highly hydrophobic surfaces (contact angle > 110°) on three resins and moderate hydrophobicity (90-100°) on the remainder. Selective patterning of hydrophobic regions in an open 3D-printed microchannel was possible in combination with simple masking techniques. Thus, this facile fluorination strategy is expected to be applicable for resin-printed materials in a variety of contexts including micropatterning and multiphase microfluidics.

3D Printing-A "Touch-Button" Approach to Manufacture Microneedles for Transdermal Drug Delivery

Microneedles (MNs) represent the concept of attractive, minimally invasive puncture devices of micron-sized dimensions that penetrate the skin painlessly and thus facilitate the transdermal administration of a wide range of active substances. MNs have been manufactured by a variety of production technologies, from a range of materials, but most of these manufacturing methods are time-consuming and expensive for screening new designs and making any modifications. Additive manufacturing (AM) has become one of the most revolutionary tools in the pharmaceutical field, with its unique ability to manufacture personalized dosage forms and patient-specific medical devices such as MNs. This review aims to summarize various 3D printing technologies that can produce MNs from digital models in a single step, including a survey on their benefits and drawbacks. In addition, this paper highlights current research in the field of 3D printed MN-assisted transdermal drug delivery systems and analyzes parameters affecting the mechanical properties of 3D printed MNs. The current regulatory framework associated with 3D printed MNs as well as different methods for the analysis and evaluation of 3D printed MN properties are outlined.

Hydrophilic modification of SLA 3D printed droplet generators by photochemical grafting

Few droplet generators manufactured using desktop stereolithography 3D printers have been reported in the literature. Moreover, 3D printed microfluidic chips are typically hydrophobic, limiting their application to water in oil droplets. Herein, we present designs for concentric and planar 3D printed microfluidic devices suitable for making polymeric microparticles using an off-the-shelf commercial stereolithography printer and resin. The devices consist of a microscope slide, binder clips, and printed components. Channels were modified by an ultraviolet grafting of methacrylic acid to the surface of chips, yielding a hydrophilic coating without modification to the bulk polymer. The water contact angle decreased from 97.0° to 25.4° after grafting. The presence of the coating was confirmed by microscopy and spectroscopy techniques. Polystyrene microparticles in the <100 μm size range were generated with varying molecular weights using the described microfluidic chips. Our work provides a facile method to construct droplet generators from commercial stereolithography printers and resins, and a rapid surface modification technique that has been under-utilized in 3D printed microfluidics. A wide range of microfluidic devices for other applications can be engineered using the methods described.

A versatile method of manufacturing and directly modifying the surfaces of 3D printed microfluidic devices was developed. The device functionality was demonstrated by producing o/w emulsions that yielded polystyrene microspheres.

Bioinstructive Layer-by-Layer-Coated Customizable 3D Printed Perfusable Microchannels Embedded in Photocrosslinkable Hydrogels for Vascular Tissue Engineering

The development of complex and large 3D vascularized tissue constructs remains the major goal of tissue engineering and regenerative medicine (TERM). To date, several strategies have been proposed to build functional and perfusable vascular networks in 3D tissue-engineered constructs to ensure the long-term cell survival and the functionality of the assembled tissues after implantation. However, none of them have been entirely successful in attaining a fully functional vascular network. Herein, we report an alternative approach to bioengineer 3D vascularized constructs by embedding bioinstructive 3D multilayered microchannels, developed by combining 3D printing with the layer-by-layer (LbL) assembly technology, in photopolymerizable hydrogels. Alginate (ALG) was chosen as the ink to produce customizable 3D sacrificial microstructures owing to its biocompatibility and structural similarity to the extracellular matrices of native tissues. ALG structures were further LbL coated with bioinstructive chitosan and arginine–glycine–aspartic acid-coupled ALG multilayers, embedded in shear-thinning photocrosslinkable xanthan gum hydrogels and exposed to a calcium-chelating solution to form perfusable multilayered microchannels, mimicking the biological barriers, such as the basement membrane, in which the endothelial cells were seeded, denoting an enhanced cell adhesion. The 3D constructs hold great promise for engineering a wide array of large-scale 3D vascularized tissue constructs for modular TERM strategies.

Go with the flow: modeling unique biological flows in engineered in vitro platforms

Interest in recapitulating in vivo phenomena in vitro using organ-on-a-chip technology has grown rapidly and with it, attention to the types of fluid flow experienced in the body has followed suit. These platforms offer distinct advantages over in vivo models with regards to human relevance, cost, and control of inputs (e.g., controlled manipulation of biomechanical cues from fluid perfusion). Given the critical role biophysical forces play in several tissues and organs, it is therefore imperative that engineered in vitro platforms capture the complex, unique flow profiles experienced in the body that are intimately tied with organ function. In this review, we outline the complex and unique flow regimes experienced by three different organ systems: blood vasculature, lymphatic vasculature, and the intestinal system. We highlight current state-of-the-art platforms that strive to replicate physiological flows within engineered tissues while introducing potential limitations in current approaches.

Breaking the Third Wall: Implementing 3D-Printing Technics to Expand the Complexity and Abilities of Multi-Organ-on-a-Chip Devices

The understanding that systemic context and tissue crosstalk are essential keys for bridging the gap between in vitro models and in vivo conditions led to a growing effort in the last decade to develop advanced multi-organ-on-a-chip devices. However, many of the proposed devices have failed to implement the means to allow for conditions tailored to each organ individually, a crucial aspect in cell functionality. Here, we present two 3D-print-based fabrication methods for a generic multi-organ-on-a-chip device: One with a PDMS microfluidic core unit and one based on 3D-printed units. The device was designed for culturing different tissues in separate compartments by integrating individual pairs of inlets and outlets, thus enabling tissue-specific perfusion rates that facilitate the generation of individual tissue-adapted perfusion profiles. The device allowed tissue crosstalk using microchannel configuration and permeable membranes used as barriers between individual cell culture compartments. Computational fluid dynamics (CFD) simulation confirmed the capability to generate significant differences in shear stress between the two individual culture compartments, each with a selective shear force. In addition, we provide preliminary findings that indicate the feasibility for biological compatibility for cell culture and long-term incubation in 3D-printed wells. Finally, we offer a cost-effective, accessible protocol enabling the design and fabrication of advanced multi-organ-on-a-chip devices.

Investigation on hot melt extrusion and prediction on 3D printability of pharmaceutical grade polymers

The development of printable filaments has been identified as a critical aspect for the processing of pharmaceutical grade polymers and the fabrication of oral solid dosage forms. In this study a range of plain and drug loaded polymers were investigated and assessed for their printability in comparison to commercial filaments. Physicochemical characterizations of the polymers included differential scanning calorimetry (DSC) thermogravimetric analysis (TGA) and rheology were studied prior to Hot Melt Extrusion processing for the filament fabrication. A texture analyser was used to study the filament mechanical properties in order to derive the maximum tensile strength, Young's Modulus and elongation at break. Principal component analysis was used to compare the printability of the polymer and to identify the contribution of each mechanical property. The analysis showed that maximum tensile strength with a threshold between 15 and 20 MPa is the most critical property for the prediction of the printability. Furthermore, printable filaments were processed using Fusion Deposition Modelling technology and optimal printing parameters were identified. The study demonstrated that the prediction of filament printability is feasible by evaluating the mechanical properties.

A review on acoustic field-driven micromixers

A review on acoustic field-driven micromixers is given. This is supplemented by the governing equations, governing non-dimensional parameters, numerical simulation approaches, and fabrication techniques. Acoustically induced vibration is a kind of external energy input employed in active micromixers to improve the mixing performance. An air bubble energized by an acoustic field acts as an external energy source and induces friction forces at the interface between an air bubble and liquid, leading to the formation of circulatory flows. The current review (with 200 references) evaluates different characteristics of microfluidic devices working based on acoustic field shaking.

One-step enzyme kinetics measurement in 3D printed microfluidics devices based on a high-performance single vibrating sharp-tip mixer

Measuring enzyme kinetics is of great importance to understand many biological processes and improve biosensing and industrial applications. Conventional methods of measuring enzyme kinetics require to prepare a series of solutions with different substrate concentrations and measure the signal response over time with these solutions, leading to tedious sample preparation steps, high reagents/sample consumption, and difficulties in studying fast enzyme kinetics. Here we report a one-step assay to measure enzyme kinetics using a 3D-printed microfluidic device, which eliminates the steps of preparing and handling multiple solutions thereby simplifying the whole workflow significantly. The assay is enabled by a highly efficient vibrating sharp-tip mixing method that can mix multiple streams of fluids with minimal mixing length (∼300 μm) and time (as low as 3 ms), and a wide range of working flow rates from 1.5 μL/min to 750 μL/min. Owing to the high performance of the mixer, a series of experiments with different substrate concentrations are performed by simply adjusting the flow rates of reagents loaded from three inlets in one experiment run. The Michaelis-Menten kinetics of the horseradish peroxidase (HRP)-catalyzed reaction between H₂O₂ and amplex red is measured in this system. The calculated Michaelis constant is consistent with the values from literature and conventional analysis methods. Due to the simplicity in fabrication and operation, rapid analysis, low power consumption (1.4-45.0 mW), and high temporal resolution, this method will significantly facilitate enzyme kinetics measurement, and offers great potential for optimizing enzyme based biosensing experiments and probing many biochemical processes.

Improving selective channel occlusion of complex hydrocarbons and fatty acid methyl esters in urea crystals by using an expendable 3D-printed microfluidic device for sample preparation in untargeted petroleomics

In this study, we describe a proof-of-concept investigation of the potential and limitations of employing channel occlusion for sample preparation in untargeted analysis in petroleomics. A middle petroleum distillate composed of fatty acid methyl esters (FAME) and a complex mixture of linear, branched, and cyclic hydrocarbons were selected as the model samples for this investigation. A microfluidic device was engineered to overcome the limitations of channel occlusion, resulting in a quick and robust method for sample preparation. The 3D-printed device using fused deposition modelling (FDM) allowed the combination of a 13-h multi-step sample handling protocol into a 2-min single-step procedure, which is also automation-friendly. Such developments were also evaluated using the analytical eco-scale to guide the development of a green analytical method. The relative standard deviation decreased 2-fold with method miniaturization. The efficiency of n-alkane removal was extended from tridecane (n-C₁₃) to heptadecane (n-C₁₇), compared to original method (n-C₁₆ to n-C₁₇). The analytical performance of the method was investigated for untargeted analysis. The tool used to probe the intra- and inter-class variance was multi-way principal component analysis (MPCA). MPCA modelling revealed that both methods generated equivalent chemical information, highlighting the benefits of reliable and reproducible sample preparation methods, especially for untargeted analysis. Such awareness is critical to avoid the generation of misleading results in fields that heavily rely on untargeted analysis and fingerprinting, such as petroleomics.

Rapid Production of PDMS Microdevices for Electrodriven Separations and Microfluidics by 3D-Printed Scaffold Removal

In our work, we produced PDMS-based microfluidic devices by mechanical removal of 3D-printed scaffolds inserted in PDMS. Two setups leading to the fabrication of monolithic PDMS-based microdevices and bonded (or stamped) PDMS-based microdevices were designed. In the monolithic devices, the 3D-printed scaffolds were fully inserted in the PDMS and then carefully removed. The bonded devices were produced by forming imprints of the 3D-printed scaffolds in PDMS, followed by bonding the PDMS parts to glass slides. All these microfluidic devices were then successfully employed in three proof-of-concept applications: capture of magnetic microparticles, formation of droplets, and isotachophoresis separation of model organic dyes.

Review of 3D-Printed functionalized devices for chemical and biochemical analysis

Recent developments in three-dimensional printing (3DP) have attracted the attention of analytical scientists interested in fabricating 3D devices having promising geometric functions to achieve desirable analytical performance. To break through the barrier of limited availability of 3DP materials and to extend the chemical reactivity and functionalities of devices manufactured using conventional 3DP, new approaches are being developed for the functionalization of 3D-printed devices for chemical and biochemical analysis. This Review discusses recent advances in the chemical functionalization schemes used in the main 3DP technologies, including (i) post-printing modification and surface immobilization of reactive substances on printed materials, (ii) pre-printing incorporation of reactive substances into raw printing materials, and (iii) combinations of both strategies, and their effects on the selectivity and/or sensitivity of related analytical methods. In addition, the state of the art of 3D-printed functionalized analytical devices for enzymatic derivatization and sensing, electrochemical sensing, and sample pretreatment applications are also reviewed, highlighting the importance of introducing new functional and functionalized materials to facilitate future 3DP-enabled manufacturing of multifunctional analytical devices.

Recent Advances and Future Perspectives on Microfluidic Mix-and-Jet Sample Delivery Devices

The integration of the Gas Dynamic Virtual Nozzle (GDVN) and microfluidic technologies has proven to be a promising sample delivery solution for biomolecular imaging studies and has the potential to be transformative for a range of applications in physics, biology, and chemistry. Here, we review the recent advances in the emerging field of microfluidic mix-and-jet sample delivery devices for the study of biomolecular reaction dynamics. First, we introduce the key parameters and dimensionless numbers involved in their design and characterisation. Then we critically review the techniques used to fabricate these integrated devices and discuss their advantages and disadvantages. We then summarise the most common experimental methods used for the characterisation of both the mixing and jetting components. Finally, we discuss future perspectives on the emerging field of microfluidic mix-and-jet sample delivery devices. In summary, this review aims to introduce this exciting new topic to the wider microfluidics community and to help guide future research in the field.

Glioma-on-a-Chip Models

Glioma, as an aggressive type of cancer, accounts for virtually 80% of malignant brain tumors. Despite advances in therapeutic approaches, the long-term survival of glioma patients is poor (it is usually fatal within 12-14 months). Glioma-on-chip platforms, with continuous perfusion, mimic in vivo metabolic functions of cancer cells for analytical purposes. This offers an unprecedented opportunity for understanding the underlying reasons that arise glioma, determining the most effective radiotherapy approach, testing different drug combinations, and screening conceivable side effects of drugs on other organs. Glioma-on-chip technologies can ultimately enhance the efficacy of treatments, promote the survival rate of patients, and pave a path for personalized medicine. In this perspective paper, we briefly review the latest developments of glioma-on-chip technologies, such as therapy applications, drug screening, and cell behavior studies, and discuss the current challenges as well as future research directions in this field.

Mechanical Properties of FDM Printed PLA Parts before and after Thermal Treatment

Fused deposition modeling (FDM) is one of the most often-used technologies in additive manufacturing. Several materials are used with this technology, such as poly(lactic acid) (PLA), which is most commonly applied. The mechanical properties of 3D-printed parts depend on the process parameters. This is why, in this study, three-point bending tests were carried out to characterize the influence of build orientation, layer thickness, printing temperature and printing speed on the mechanical properties of PLA samples. Not only the process parameters may affect the mechanical properties, but heat after-treatment also has an influence on them. For this reason, additional samples were printed with optimal process parameters and characterized after pure heat treatment as well as after deformation at a temperature above the glass transition temperature, cooling with applied deformation, and subsequent recovery under heat treatment. These findings are planned to be used in a future study on finger orthoses that could either be printed according to shape or in a flat shape and afterwards heated and bent around the finger.