Joel Segal

A novel technique for the production of electrospun scaffolds with tailored three-dimensional micro-patterns employing additive manufacturing

Electrospinning is a common technique used to fabricate fibrous scaffolds for tissue engineering applications. There is now growing interest in assessing the ability of collector plate design to influence the patterning of the fibres during the electrospinning process. In this study, we investigate a novel method to generate hybrid electrospun scaffolds consisting of both random fibres and a defined three-dimensional (3D) micro-topography at the surface, using patterned resin formers produced by rapid prototyping (RP). Poly(D,L-lactide-co-glycolide) was electrospun onto the engineered RP surfaces and the ability of these formers to influence microfibre patterning in the resulting scaffolds visualized by scanning electron microscopy. Electrospun scaffolds with patterns mirroring the microstructures of the formers were successfully fabricated. The effect of the resulting fibre patterns and 3D geometries on mammalian cell adhesion and proliferation was investigated by seeding enhanced green fluorescent protein labelled 3T3 fibroblasts onto the scaffolds. Following 24 h and four days of culture, the seeded scaffolds were visually assessed by confocal macro- and microscopy. The patterning of the fibres guided initial cell adhesion to the scaffold with subsequent proliferation over the geometry resulting in the cells being held in a 3D micro-topography. Such patterning could be designed to replicate a specific in vivo structure; we use the dermal papillae as an exemplar here. In conclusion, a novel, versatile and scalable method to produce hybrid electrospun scaffolds has been developed. The 3D directional cues of the patterned fibres have been shown to influence cell behaviour and could be used to culture cells within a similar 3D micro-topography as experienced in vivo.

Rapid manufacturing of non-assembly complex micro-devices by microstereolithography

This paper introduces a non-assembly manufacturing case with microstereolithography technology. The design and manufacturing process of a pneumatic thrust bearing is described, and a special tessellation method is developed to further improve the capability of the manufacturing system thus bigger products can also be easily manufactured. Implemented in a layer-by-layer fashion, stereolithography has been used for the rapid manufacturing of complex devices, and it avoids the expensive assembly process in the traditional manufacturing. This paper presents that microstereolithography can produce high-resolution products with intricate details, small openings, and smooth surfaces. The potential of the microstereolithograhy technique is explored for the rapid manufacturing of small and complex objects.

A review of research into the effects of rapid tooling on part properties

Rapid prototyping technologies have introduced a new generation of rapid tooling processes. Many of these rapid tools have been used for injection moulding where the thermal properties of the tool material are critical to the quality of parts produced. Rapid tools are often made from materials with substantially different thermal properties than conventional metal tools. Engineers wishing to make use of these technologies to produce technical prototypes must be aware of the effect this will have on final part properties. Some previous research has been undertaken in this area. Reviews the work done in the field of rapid tooling used for injection moulding. The review shows that, whereas a range of techniques and final part materials has been studied, the results obtained are incomplete and often unexplained. The authors draw conclusions as to why this is so and go on to identify areas for further work that will be pursued.

A 3D bioprinting exemplar of the consequences of the regulatory requirements on customized processes.

Computer-aided 3D printing approaches to the industrial production of customized 3D functional living constructs for restoration of tissue and organ function face significant regulatory challenges. Using the manufacture of a customized, 3D-bioprinted nasal implant as a well-informed but hypothetical exemplar, we examine how these products might be regulated. Existing EU and USA regulatory frameworks do not account for the differences between 3D printing and conventional manufacturing methods or the ability to create individual customized products using mechanized rather than craft approaches. Already subject to extensive regulatory control, issues related to control of the computer-aided design to manufacture process and the associated software system chain present additional scientific and regulatory challenges for manufacturers of these complex 3D-bioprinted advanced combination products.

Improving umbilical cord blood processing to increase total nucleated cell count yield and reduce cord input wastage by managing the consequences of input variation

BACKGROUND AIMS With the rising use of umbilical cord blood (UCB) as an alternative source of hematopoietic stem cells, storage inventories of UCB have grown, giving rise to genetically diverse inventories globally. In the absence of reliable markers such as CD34 or counts of colony-forming units, total nucleated cell (TNC) counts are often used as an indicator of potency, and transplant centers worldwide often select units with the largest counts of TNC. As a result, cord blood banks are driven to increase the quality of stored inventories by increasing the TNC count of products stored. However, these banks face challenges in recovering consistent levels of TNC with the use of the standard protocols of automated umbilical cord processing systems, particularly in the presence of input variation both of cord blood volume and TNC count, in which it is currently not possible to process larger but useable UCB units with consequent losses in TNC. METHODS This report addresses the challenge of recovering consistently high TNC yields in volume reduction by proposing and validating an alternative protocol capable of processing a larger range of units more reliably. RESULTS This work demonstrates improvements in plastic ware and tubing sets and in the recovery process protocol with consequent productivity gains in TNC yield and a reduction in standard deviation. CONCLUSIONS This work could pave the way for cord blood banks to improve UCB processing and increase efficiency through higher yields and lower costs.

Impact of an educational intervention upon the hand hygiene compliance of children

BACKGROUND Hand hygiene compliance is the single most effective way to reduce healthcare-associated infections. Children are notoriously vulnerable to infection as well as acting as conduits to transmission. Based on these observations, the authors formulated the hypothesis that behavioural change which improved childrens hand hygiene compliance would decrease the spread of infectious diseases. AIM To create an educational intervention to induce long-term behavioural change culminating in increased hand hygiene compliance of children, and thus a decrease in the rate of infections. METHODS Focus groups conducted during interactive teaching sessions identified what children felt would help them to increase their hand hygiene compliance. This informed the design of an educational device that was subsequently trialled to measure its effectiveness in increasing hand hygiene compliance. Initial developmental stages were conducted in two schools in the East Midlands with study participants aged 5-8 years; the device was subsequently used in a healthcare setting to assess deployment flexibility. FINDINGS Focus groups indicated that children enjoyed interactive learning, developed knowledge about cross-transmission of infections, and became motivated to encourage others to improve hand hygiene compliance. Microbiological swabbing verified the presence of pathogens on childrens hands and environmental surfaces that could serve as reservoirs of infection, and questionnaires indicated an increase in handwashing following the intervention. CONCLUSION Educational interventions have the potential to increase hand hygiene and reduce the transmission of infections.

Fibre laser metal deposition with wire: parameters study and temperature monitoring system

This paper addresses the development of a laser metal deposition process which consists of a 2 kW Fibre Laser, a CNC table, a wire feeder and a temperature monitoring system. During its development, six infrared pyrometers were tried to compare their performance. The system utilizes two pyrometers to measure both the melt-pool and workpiece (upper layer) temperatures. Experiments have been performed to study the metal deposition parameters with stainless steel 308L wire deposited on stainless steel 304, and good quality metal deposition has been achieved. The results of the parameters study and the development of the temperature monitoring system are presented.

Degradation and Characterization of Resorbable Phosphate-Based Glass Thin-Film Coatings Applied by Radio-Frequency Magnetron Sputtering

Quinternary phosphate-based glasses of up to 2.67 μm, deposited by radio-frequency magnetron sputtering, were degraded in distilled water and phosphate-buffered saline (PBS) to investigate their degradation characteristics. Magnetron-sputtered coatings have been structurally compared to their compositionally equivalent melt-quenched bulk glass counterparts. The coatings were found to have structurally variable surfaces to melt-quenched glass such that the respective bridging oxygen to nonbridging oxygen bonds were 34.2% to 65.8% versus 20.5% to 79.5%, forming metaphosphate (PO3)(-) (Q(2)) versus less soluble (P2O7)(4-) (Q(1)) and (PO4)(3-) (Q(0)), respectively. This factor led to highly soluble coatings, exhibiting a t(1/2) degradation dependence in the first 2 h in distilled water, followed by a more characteristic linear profile because the subsequent layers were less soluble. Degradation was observed to preferentially occur, forming voids characteristic of pitting corrosion, which was confirmed by the use of a focused ion beam. Coating degradation in PBS precipitated a (PO3)(-) metaphosphate, an X-ray amorphous layer, which remained adherent to the substrate and seemingly formed a protective diffusion barrier, which inhibited further coating degradation. The implications are that while compositionally similar, sputter-deposited coatings and melt-quenched glasses are structurally dissimilar, most notably, with regard to the surface layer. This factor has been attributed to surface etching of the as-deposited coating layer during deposition and variation in the thermal history between the processes of magnetron sputtering and melt quenching.

Growth of the chorioallantoic membrane into a rapid-prototyped model pore system: experiments and mathematical model

This paper presents a mathematical model to describe the growth of tissue into a rapid-prototyped porous scaffold when it is implanted onto the chorioallantoic membrane (CAM). The scaffold was designed to study the effects of the size and shape of pores on tissue growth into conventional tissue engineering scaffolds, and consists of an array of pores each having a pre-specified shape. The experimental observations revealed that the CAM grows through each pore as an intact layer of tissue, provided the width of the pore exceeds a threshold value. Based on these results a mathematical model is described to simulate the growth of the membrane, assuming that the growth is a function of the local isotropic membrane tension. The model predictions are compared against measurements of the extent of membrane growth through the pores as a function of time for pores with different dimensions.

Effects of the Cutting Tool Edge Radius on the Stability Lobes in Micro-Milling

This paper investigates the effects of the cutting tool edge radius on the cutting forces and stability lobes in micro-milling. The investigation is conducted based on recently developed models for prediction of micro-milling cutting forces and stability lobes. The developed models consider the nonlinearities of the micro-milling process, such as nonlinear cutting forces due to cutting velocity dependencies, edge radius effect and run-out presence. A number of finite element analyses (FEA) are performed to obtain the cutting forces in orthogonal cutting which are used for determining the micro-milling cutting forces. The chip morphology obtained for different tool edge radii using FEA is presented. It is observed that at large tool edge radii the influence of the ploughing effect become more significant factor on the chip morphology. The results related to micro-milling cutting forces and stability lobes show that by enlarging the tool edge radius the micro-milling cutting forces increase while the stability limits decrease.