An integrative review on the applications of 3D printing in the field of in vitro diagnostics

Variations in the Thermomechanical and Structural Properties during the Cooling of Shape-Memory R-PETG

One of the useful features of 3D-printed specimens of recycled polyethylene terephthalate glycol (R-PETG) is the ability to repetitively develop free recovery as well as the work-generating, shape-memory effect. This behavior is enabled by the R-PETG's capacity to stiffen during cooling, thus allowing for a new temporary shape to be induced. Aiming to devise an explanation for the polymer's stiffening, in this study, the variation in some of the R-PETG's parameters during cooling are emphasized and discussed. The evolution of an R-PETG filament's shape was monitored during room-temperature-bending heating-cooling cycles. Straight-shape recovery and the complete loss of stiffness were observed at the start and the end of heating, respectively, followed by the forced straightening of the filament, performed by the operator, around 40 °C, during cooling. The tests performed by dynamic mechanical analysis disclosed the rise of the storage modulus (E') after 100 °C heating followed by either liquid-nitrogen- or air-cooling to room temperature, in such a way that E' was always larger after cooling than initially. Static tests emphasized a peculiar stress variation during a heating-cooling cycle applied in air, within the heating chamber of the tensile testing machine. Tensile-failure tests were performed at -10 °C at a rate of 100 mm/min, with specimens printed at various deposition directions between 10 and 40° to the transversal direction. The specimens printed at 40°, which had the largest ultimate strains, were broken with tensile rates between 100 and 500 mm/min. Deformation rate increase favored the shift from crazing to delamination failure modes. The correlation between the structural changes, the sharp E' increase on heating, and the stiffening induced by cooling represents a novel approach that enables the use of 3D-printed R-PETG for the fabrication of the active parts of low-priced lightweight resettable actuators.

Science and Technology of Additive Manufacturing Progress: Processes, Materials, and Applications

As a special review article, several significant and applied results in 3D printing and additive manufacturing (AM) science and technology are reviewed and studied. Which, the reviewed research works were published in 2020. Then, we would have another review article for 2021 and 2022. The main purpose is to collect new and applied research results as a useful package for researchers. Nowadays, AM is an extremely discussed topic and subject in scientific and industrial societies, as well as a new vision of the unknown modern world. Also, the future of AM materials is toward fundamental changes. Which, AM would be an ongoing new industrial revolution in the digital world. With parallel methods and similar technologies, considerable developments have been made in 4D in recent years. AM as a tool is related to the 4th industrial revolution. So, AM and 3D printing are moving towards the fifth industrial revolution. In addition, a study on AM is vital for generating the next developments, which are beneficial for human beings and life. Thus, this article presents the brief, updated, and applied methods and results published in 2020.

Graphical Abstract

Calcium Carbonate Coating of 3D-Printed PLA Scaffolds Intended for Biomedical Applications

The incorporation of ceramic additives is the most commonly used strategy to improve the biofunctionality of polymer-based scaffolds intended for bone regeneration. By embedding ceramic particles as a coating, the functionality improvement in the polymeric scaffolds can be concentrated on the cell-surface interface, thus creating a more favourable environment for the adhesion and proliferation of osteoblastic cells. In this work, a pressure-assisted and heat-induced method to coat polylactic acid (PLA) scaffolds with calcium carbonate (CaCO₃) particles is presented for the first time. The coated scaffolds were evaluated by optical microscopy observations, a scanning electron microscopy analysis, water contact angle measurements, compression testing, and an enzymatic degradation study. The ceramic particles were evenly distributed, covered more than 60% of the surface, and represented around 7% of the coated scaffold weight. A strong bonding interface was achieved, and the thin layer of CaCO₃ (~20 µm) provided a significant increase in the mechanical properties (with a compression modulus improvement up to 14%) while also enhancing the surface roughness and hydrophilicity. The results of the degradation study confirmed that the coated scaffolds were able to maintain the pH of the media during the test (~7.6 ± 0.1), in contrast to the pure PLA scaffolds, for which a value of 5.07 ± 0.1 was obtained. The ceramic-coated scaffolds developed showed potential for further evaluations in bone tissue engineering applications.

On the Thermomechanical Behavior of 3D-Printed Specimens of Shape Memory R-PETG

From commercial pellets of recycled polyethylene terephthalate glycol (R-PETG), 1.75 mm diameter filaments for 3D printing were produced. By varying the filament's deposition direction between 10° and 40° to the transversal axis, parallelepiped specimens were fabricated by additive manufacturing. When bent at room temperature (RT), both the filaments and the 3D-printed specimens recovered their shape during heating, either without any constraint or while lifting a load over a certain distance. In this way, free-recovery and work-generating shape memory effects (SMEs) were developed. The former could be repeated without any visible fatigue marks for as much as 20 heating (to 90 °C)-RT cooling-bending cycles, while the latter enabled the lifting of loads over 50 times heavier than the active specimens. Tensile static failure tests revealed the superiority of the specimens printed at larger angles over those printed at 10°, since the specimens printed at 40° had tensile failure stresses and strains over 35 MPa and 8.5%, respectively. Scanning electron microscopy (SEM) fractographs displayed the structure of the successively deposited layers and a shredding tendency enhanced by the increase in the deposition angle. Differential scanning calorimetry (DSC) analysis enabled the identification of the glass transition between 67.5 and 77.3 °C, which might explain the occurrence of SMEs in both the filament and 3D-printed specimens. Dynamic mechanical analysis (DMA) emphasized a local increase in storage modulus of 0.87-1.66 GPa that occurred during heating, which might explain the development of work-generating SME in both filament and 3D-printed specimens. These properties recommend 3D-printed parts made of R-PETG as active elements in low-price lightweight actuators operating between RT and 63 °C.

Application of three dimensional-printed devices in extraction technologies

Sample pretreatment is an important and necessary process in chemical analysis. Traditional sample preparation methods normally consume moderate to large quantities of solvents and reagents, are time- and labor-intensive and can be prone to error (since they usually involve multiple steps). In the past quarter century or so, modern sample preparation techniques have evolved, from the advent of solid-phase microextraction and liquid-phase microextraction to the present day where they are now widely applied to extract analytes from simple as well as complex matrices leveraging on their extremely low solvent consumption, high extraction efficiency, generally straightforward and simple operation and integration of most, if not all, of the following aspects: Sampling, cleanup, extraction, preconcentration and ready-to-inject status of the final extract. One of the most interesting features of the progress of microextraction techniques over the years lies in the development of devices, apparatus and tools to facilitate and improve their operations. This review explores the application of a recent material fabrication technology that has been receiving a lot of interest, that of three-dimensional (3D) printing, to the manipulation of microextraction. The review highlights the use of 3D-printed devices in the extraction of various analytes and in different methods to address, and improves upon some current extraction (and microextraction) problems, issues and concerns.

Deep learning on lateral flow immunoassay for the analysis of detection data

Lateral flow immunoassay (LFIA) is an important detection method in vitro diagnosis, which has been widely used in medical industry. It is difficult to analyze all peak shapes through classical methods due to the complexity of LFIA. Classical methods are generally some peak-finding methods, which cannot distinguish the difference between normal peak and interference or noise peak, and it is also difficult for them to find the weak peak. Here, a novel method based on deep learning was proposed, which can effectively solve these problems. The method had two steps. The first was to classify the data by a classification model and screen out double-peaks data, and second was to realize segmentation of the integral regions through an improved U-Net segmentation model. After training, the accuracy of the classification model for validation set was 99.59%, and using combined loss function (WBCE + DSC), intersection over union (IoU) value of segmentation model for validation set was 0.9680. This method was used in a hand-held fluorescence immunochromatography analyzer designed independently by our team. A Ferritin standard curve was created, and the T/C value correlated well with standard concentrations in the range of 0-500 ng/ml (R ² = 0.9986). The coefficients of variation (CVs) were ≤ 1.37%. The recovery rate ranged from 96.37 to 105.07%. Interference or noise peaks are the biggest obstacle in the use of hand-held instruments, and often lead to peak-finding errors. Due to the changeable and flexible use environment of hand-held devices, it is not convenient to provide any technical support. This method greatly reduced the failure rate of peak finding, which can reduce the customer's need for instrument technical support. This study provided a new direction for the data-processing of point-of-care testing (POCT) instruments based on LFIA.

Three-dimensional printing in ophthalmology and eye care: current applications and future developments

Three-dimensional (3D) printing uses a process of adding material in a layer-by-layer fashion to form the end product. This technology is advancing rapidly and is being increasingly utilized in the medical field as it becomes more accessible and cost-effective. It has an increasingly important role in ophthalmology and eyecare as its current and potential applications are extensive and slowly evolving. Three-dimensional printing represents an important method of manufacturing customized products such as orbital implants, ocular prostheses, ophthalmic models, surgical instruments, spectacles and other gadgets. Surgical planning, simulation, training and teaching have all benefitted from this technology. Advances in bioprinting seem to be the future direction of 3D printing with possibilities of printing out viable ocular tissues such as corneas and retinas in the future. It is expected that more ophthalmologists and other clinicians will use this technology in the near future.

A survey of 3D printing technology applied to paper microfluidics

Paper microfluidics is a rapidly growing subfield of microfluidics in which paper-like porous materials are used to create analytical devices that are well-suited for use in field applications. 3D printing technology has the potential to positively affect paper microfluidic device development by enabling tools and methods for the creation of devices with well-defined and tunable fluidic networks of porous matrices for high performance signal generation. This critical review focuses on the progress that has been made in using 3D printing technologies to advance the development of paper microfluidic devices. We describe printing work in three general categories: (i) solid support structures for paper microfluidic device components; (ii) channel barrier definition in existing porous materials; and (iii) porous channels for capillary flow, and discuss their value in advancing paper microfluidic device development. Finally, we discuss major areas of focus for highest impact on the next generation of paper microfluidics devices.

Mathematical Analysis of Application of a Three-Dimensional Printing Fixator in the Fracture of Multiple Ribs

Data were obtained from 66 clinical patients. The patients were divided into a non-3D printing group (control group) and a 3D printing group (intervention group) in a 1 : 1 ratio, with 33 patients in each group. The information including gender, age, incision length, number of surgical roots, bleeding volume, operation time, and intraoperative blood transfusion was collected for SPSS analysis. The results showed the following: (1) The paired t-test was used to test the difference of experimental data. There was a significant difference of 0.01 between the incision length/surgical root number in the intervention group and the incision length/surgical root number in the control group. The incision length/surgical root number in the intervention group was significantly lower than that in the control group. (2) Surgical time, intraoperative blood transfusion, age, and incision length/surgical root number in the intervention group had a significant positive impact on the amount of bleeding. Gender did not affect the amount of bleeding. (3) A total of 1 item of operation time in the intervention group had a significant positive impact on intraoperative blood transfusion. (4) The incision length/number of surgical roots in the intervention group had a noteworthy negative impact on blood transfusion during the operation.