During the resorbable-polymer-boom of the 1970s and 1980s, polycaprolactone (PCL) was used in the biomaterials field and a number of drug-delivery devices. Its popularity was soon superseded by faster resorbable polymers which had fewer perceived disadvantages associated with long term degradation (up to 3-4 years) and intracellular resorption pathways; consequently, PCL was almost forgotten for most of two decades. Recently, a resurgence of interest has propelled PCL back into the biomaterials-arena. The superior rheological and viscoelastic properties over many of its aliphatic polyester counterparts renders PCL easy to manufacture and manipulate into a large range of implants and devices. Coupled with relatively inexpensive production routes and FDA approval, this provides a promising platform for the production of longer-term degradable implants which may be manipulated physically, chemically and biologically to possess tailorable degradation kinetics to suit a specific anatomical site. This review will discuss the application of PCL as a biomaterial over the last two decades focusing on the advantages which have propagated its return into the spotlight with a particular focus on medical devices, drug delivery and tissue engineering.

The return of a forgotten polymer : Polycaprolactone in the 21st century

Vaccine cold chain management and cold storage technology to address the challenges of vaccination programs

The aim of this paper was to design and fabricate a novel composite scaffold based on the combination of 3D-printed polylactic acid-based triply periodic minimal surfaces (TPMSs) and cell-laden alginate hydrogel. This novel scaffold improves the low mechanical properties of alginate hydrogel and can also provide a scaffold with a suitable pore size, which can be used in bone regeneration applications. In this regard, an implicit function was used to generate some gyroid TPMS scaffolds. Then the fused deposition modeling process was employed to print the scaffolds. Moreover, the micro computed tomography technique was employed to assess the microstructure of 3D-printed TPMS scaffolds and obtain the real geometries of printed scaffolds. The mechanical properties of composite scaffolds were investigated under compression tests experimentally. It was shown that different mechanical behaviors could be obtained for different implicit function parameters. In this research, to assess the mechanical behavior of printed scaffolds in terms of the strain-stress curves on, two approaches were presented: equivalent volume and finite element-based volume. Results of strain-stress curves showed that the finite-element based approach predicts a higher level of stress. Moreover, the biological response of composite scaffolds in terms of cell viability, cell proliferation, and cell attachment was investigated. In this vein, a dynamic cell culture system was designed and fabricated, which improves mass transport through the composite scaffolds and applies mechanical loading to the cells, which helps cell proliferation. Moreover, the results of the novel composite scaffolds were compared to those without alginate, and it was shown that the composite scaffold could create more viability and cell proliferation in both dynamic and static cultures. Also, it was shown that scaffolds in dynamic cell culture have a better biological response than in static culture. In addition, scanning electron microscopy was employed to study the cell adhesion on the composite scaffolds, which showed excellent attachment between the scaffolds and cells. 

In vitro static and dynamic cell culture study of novel bone scaffolds based on 3D-printed PLA and cell-laden alginate hydrogel

Phase change materials (PCMs) have become a research hotspot in the field of energy storage due to their high energy storage density. Fruits and vegetables have the characteristics of perishability, temperature sensitivity, and cross-regional transportation, which makes their transportation and distribution technical requirements higher. Traditional mechanical refrigeration is prone to temperature fluctuation and high carbon emission during transportation. Therefore, PCMs has great application potential in the cold chain transportation of fruits and vegetables, and its application will help improve food safety and save energy. This paper analyzes the characteristics of fruit and vegetable cold chain logistics, and introduces the composition of the cold storage box, summarizes the application and research of phase change cold storage technology in cold chain transportation. A summary analysis including the refrigeration, temperature control, heat insulation, and energy-saving effects of PCMs, points out the research prospects of transportation equipment and problems that need to be solved, and provides a reference for building a more complete and efficient cold chain transportation system for fruits and vegetables in the future. 

Research progress of cold chain transport technology for storage fruits and vegetables

Effect of the raster orientation on strength of the continuous fiber reinforced PVDF/PLA composites, fabricated by hand-layup and fused deposition modeling

The fused-deposition modeling (FDM) process is carried out at an elevated temperature, preventing the addition of biological factors, drugs, bioactive compounds, etc, during fabrication. To overcome this disadvantage, a 3D interlinked porous polylactic acid (PLA) scaffold was fabricated by FDM, followed by the embedding of a polycaprolactone (PCL) scaffold into the pores of the PLA at room temperature, yielding a PLA-PCL scaffold. In addition, PLA-PCL scaffolds with nanohydroxyapatite (PLA-PCL-nHAP) and multiwalled carbon nanotubes (PLA-PCL-MWCNT) were also fabricated. Here, the FDM-fabricated PLA scaffold functions as the structural component, whereas the embedded PCL scaffold acts as the functional component, which provides a the ability to functionalize the scaffolds with the desired chemical or biological materials. The embedding process is straightforward, cost effective, and does not require sophistication. A mechanical characterization of the scaffolds suggests that the Young's modulus of the PLA-PCL scaffold (16.02 MPa) was higher than that of the FDM-fabricated PLA (9.98 MPa) scaffold, by virtue of embedded PCL matrix. In addition, finite element analysis showed that the von Mises stress on a mandible with scaffolds was 4.04 MPa, whereas for a mandible with a defect, it was 6.7 MPa, confirming the stress distribution efficiency and mechanical stability of these scaffolds. Furthermore, field emission-scanning electron microscope analysis implied the presence of interlinked porous structures with pore diameters of 50 µm to 300 µm. X-ray diffraction results revealed an increased crystallinity (%) in the embedded models (PLA-PCL, PLA-PCL-nHAP and PLA-PCL-MWCNT), compared to a PLA printed scaffold. Additionally, Raman analysis revealed that the embedding process did not cause chemical alterations in the polymeric chains. In vitro analysis with human osteoblasts demonstrated the osteoconductive nature of the scaffold, which supported mineralization. In brief, the advantage of our model is that it helps to overcome the difficulties of manufacturing a filament with the desired additives for FDM, and offers the ability to incorporate the desired concentrations of heat-labile bioactive molecules during the embedding process at ambient temperatures.

Facile manufacturing of fused-deposition modeled composite scaffolds for tissue engineering-an embedding model with plasticity for incorporation of additives.

Being thermosensitive, Vaccines need storage at specific temperatures of 2-8 °C, and Vaccine Cold chain Carriers are the most widely utilized instruments to carry out rural vaccination drives in Low-income hot climate countries. Several developed designs for the carrier have reported superior performance, but their actual penetration into rural community medicine is limited due to reasons of cost and utility. Thus, the scope for improvement in the design is significant and it is also pertinent to quantify the effect of design features on the performance. Taking shared features possessed by such superior designs, the work presents the impact of geometry, vertically stacked vaccine tray assembly and usage of Phase Change Materials(PCM), on the final passive cooler assembly. A fabricated New Design with given features is cross-compared and analysed with a Market(Original) Design of the same scale and storage capacity. Analysis performed takes a scientific inclination towards Engineering and Insulation aspects of the Vaccine Box. It uses Conjugate Heat Transfer model(CFD simulations), Geometry analysis, experimentally derived Insulation R-values and Temperature monitoring to accomplish this. Secondly, the work presents a systematic design approach to improve upon the conventional design, PCM selection is made using DSC(Differential Scanning Calorimetry) testing, and Material of Construction(MOC) selection is made using Ashby plots based on the results of the simulations. Overall the Fabricated New Design gives an improvement of ≈ 16 % in R-value and ≈ 17 % improvement in the retention time of the specific temperature range, over the conventional (Original) Design.

Enhancing the insulation capability of a vaccine carrier box: An engineering approach

Human health is one of the most important concerns for the governments around the world. Global organizations such as WHO (World Health Organization) and PATH (Program for Appropriate Technology in Health) have considerable interest in organizing vaccination programs and its cold chain delivery. The problem predominantly persists in Lower-middle income countries like India where due to inadequate infrastructure and lack of consistent Power supply, significant losses occur in the cold chain. Improvements are required to prevent the loss of costly and precious vaccines during the cold chain. India lacks a reliable power supply and the resulting power cuts interrupt the cold chain, leading to a loss of vaccine potency since they are not within the temperature range of 2–8 °C. This paper studies the current VCB (vaccine carrier box) and cold chain design through the aid of Computer modelling and simulations. Also a novel experimental setup to examine insulation R-value has been devised and studied. Based on this a new design approach is utilized to model a thermoelectric system and early designing is done through the aid of 3-D printing.Copyright © 2016 by ASME

Design and Analysis of an Efficient Vaccine Cold Chain Box

Grip strength is the function of musculotendinous action across the finger joints and varies while dealing objects of varying size and shape Increasing object size requires greater effort by the fingers to grip The main objective of this study is to analyse the variation in grip and pinch strength exerted on objects of various sizes and shapes in a short span of time OpenSim 33 is open-source musculoskeletal modelling software used for performing simulations in a dynamic environment The generic wrist model in OpenSim has movements on index finger and thumb only, for study purpose Objects of various sizes were designed and imported in OpenSim This study determines the joint moments exerted by the fingers during grip activities Original model was modified and custom joints were placed in the proximal and distal phalanx joints of the fingers This allowed the finger segments to undergo translational and rotational movements Coordinates of the custom joints were adjusted to provide constraints in the joint movement to hold the objects in position For grip strength, objects of various sizes and shapes were imported to OpenSim Simulation was carried out for gripping the objects for a specified time period The force generated by the synergistic movements of finger segments was compared among grip and pinch of different objects This method is used to determine the grip and pinch strength by handling objects of different shapes and sizes under the influence of time

Analysis of grip and pinch strength using inverse dynamics simulation technique.

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Facile manufacturing of fused-deposition modeled composite scaffolds for tissue engineering-an embedding model with plasticity for incorporation of additives.

Enhancing the insulation capability of a vaccine carrier box: An engineering approach

Design and Analysis of an Efficient Vaccine Cold Chain Box

Analysis of grip and pinch strength using inverse dynamics simulation technique.