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 Its popularity was soon superseded by faster resorbable polymers which had fewer perceived disadvantages associated with long term degradation (up to 3-4 years) and intracellular resorption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

Melt electrospun fibers of poly(ϵ-caprolactone) are accurately deposited using an automated stage as the collector. Matching the translation speed of the collector to the speed of the melt electrospinning jet establishes control over the location of fiber deposition. In this sense, melt electrospinning writing can be seen to bridge the gap between solution electrospinning and direct writing additive manufacturing processes.

Direct writing by way of melt electrospinning

Flexible tubular structures fabricated from solution electrospun fibers are finding increasing use in tissue engineering applications. However it is difficult to control the deposition of fibers due to the chaotic nature of the solution electrospinning jet. By using non-conductive polymer melts instead of polymer solutions the path and collection of the fiber becomes predictable. In this work we demonstrate the melt electrospinning of polycaprolactone in a direct writing mode onto a rotating cylinder. This allows the design and fabrication of tubes using 20 μm diameter fibers with controllable micropatterns and mechanical properties. A key design parameter is the fiber winding angle, where it allows control over scaffold pore morphology (e.g. size, shape, number and porosity). Furthermore, the establishment of a finite element model as a predictive design tool is validated against mechanical testing results of melt electrospun tubes to show that a lesser winding angle provides improved mechanical response to uniaxial tension and compression. In addition, we show that melt electrospun tubes support the growth of three different cell types in vitro and are therefore promising scaffolds for tissue engineering applications.

Design and fabrication of tubular scaffolds via direct writing in a melt electrospinning mode

Melt electrowriting (MEW) is an emerging high-resolution additive manufacturing technique based on the electrohydrodynamic processing of polymers. MEW is predominantly used to fabricate scaffolds for biomedical applications, where the microscale fiber positioning has substantial implications in its macroscopic mechanical properties. This review gives an update on the increasing number of polymers processed via MEW and different commercial sources of the gold standard poly(e-caprolactone) (PCL). A description of MEW-processed polymers beyond PCL is introduced, including blends and coated fibers to provide specific advantages in biomedical applications. Furthermore, a perspective on printer designs and developments is highlighted, to keep expanding the variety of processable polymers for MEW.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/adhm.202001232

Polymers for Melt Electrowriting

Medical robots are invaluable players in non-pharmaceutical treatment of disabilities. Particularly, using prosthetic and rehabilitation devices with human–machine interfaces can greatly improve the quality of life for impaired patients. In recent years, flexible electronic interfaces and soft robotics have attracted tremendous attention in this field due to their high biocompatibility, functionality, conformability, and low-cost. Flexible human–machine interfaces on soft robotics will make a promising alternative to conventional rigid devices, which can potentially revolutionize the paradigm and future direction of medical robotics in terms of rehabilitation feedback and user experience. In this review, the fundamental components of the materials, structures, and mechanisms in flexible human-machine interfaces are summarized by recent and renowned applications in five primary areas: physical and chemical sensing, physiological recording, information processing and communication, soft robotic actuation, and feedback stimulation. This review further concludes by discussing the outlook and current challenges of these technologies as a human–machine interface in medical robotics. 

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Flexible Electronics and Devices as Human–Machine Interfaces for Medical Robotics

Melt electrowriting (MEW) has grown in popularity in biofabrication research due to its ability to fabricate complex, high-precision networks of fibres. These fibres can mimic the morphology of a natural extracellular matrix, enabling tissue analogues for transplantation or personalised drug screening. To date, MEW has employed two different collector-plate modalities for the fabrication of constructs. Flat collector plates, typical of traditional 3D printing methods, allow for the layer-by-layer fabrication of 2D structures into complex 3D structures. Alternatively, rotating mandrels can be used for the creation of tubular scaffolds. However, unlike other additive manufacturing techniques that can immediately start and stop the extrusion of material during printing, MEW instead requires a continuous flow of polymer. Consequently, conventional g-code control software packages are unsuitable. To overcome this challenge, a suite of customised pattern generation software tools have been developed to enable the design of MEW scaffolds with highly-controlled geometry, including crosshatch, gradient porosity, tubular, and patient-specific configurations. The high level of design control using this approach enables the production of scaffolds with highly adaptable mechanical properties, as well as the potential to influence biological properties for cell attachment and proliferation.

Design tools for patient specific and highly controlled melt electrowritten scaffolds

Millions of people worldwide experience disfigurement due to cancers, congenital defects, or trauma, leading to significant psychological, social, and economic disadvantage. Prosthetics aim to reduce their suffering by restoring aesthetics and function using synthetic materials that mimic the characteristics of native tissue. In the 1900s, natural materials used for thousands of years in prosthetics were replaced by synthetic polymers bringing about significant improvements in fabrication and greater realism and utility. These traditional methods have now been disrupted by the advanced manufacturing revolution, radically changing the materials, methods, and nature of prosthetics. In this report, traditional synthetic polymers and advanced prosthetic materials and manufacturing techniques are discussed, including a focus on prosthetic material degradation. New manufacturing approaches and future technological developments are also discussed in the context of specific tissues requiring aesthetic restoration, such as ear, nose, face, eye, breast, and hand. As advanced manufacturing moves from research into clinical practice, prosthetics can begin new age to significantly improve the quality of life for those suffering tissue loss or disfigurement.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1002/adma.202001122

Past, Present, and Future of Soft-Tissue Prosthetics: Advanced Polymers and Advanced Manufacturing.

Three dimensional (3D) printing and biofabrication technologies are revolutionising medicine with low-cost and novel treatments for complex medical conditions. These approaches differ from traditional treatments by using 3D scanning, computer modelling and 3D printing to automate the production of patient-specific tissue replacement or prostheses using a wide range of materials. One area impacted by this technology is the treatment of congenital maxillofacial conditions such as microtia, a condition affecting the intrauterine development of the auricle (external ear) and with a prevalence of 2.06 cases for every 10,000 births. While not life-threatening, microtia significantly impacts the emotional and psychological wellbeing of the affected child and their parents. Current treatments include the use of prosthetic ears or surgical methods such as autografting rib cartilage or alloplastic implants. Although current options have shown documented success, they are highly dependent on the surgeon's skill and it has been demonstrated that poor quality solutions can further exacerbate negative psychosocial impacts. As such, higher quality, lower cost and more customised options would be welcomed by patients and parents alike. Recent advances in 3D scanning, modelling and printing techniques could significantly benefit the treatment and reconstructive options for children with microtia, leading to improved quality of life.

/pdf/aesthetic-reconstruction-of-microtia-a-review-of-current-3bd4i7cllo.pdf

Aesthetic reconstruction of microtia: a review of current techniques and new 3D printing approaches

Physical disfigurement due to congenital defects, trauma, or cancer causes considerable distress and physical impairment for millions of people worldwide; impacting their economic, psychological and social wellbeing. Since 3000 B.C., prosthetic devices have been used to address these issues by restoring both aesthetics and utility to those with disfigurement. Internationally, academic and industry researchers are constantly developing new materials and manufacturing techniques to provide higher quality and lower cost prostheses to those people who need them. New advanced technologies including 3D imaging, modeling, and printing are revolutionizing the way prostheses are now made. These new approaches are disrupting the traditional and manual art form of prosthetic production which are laborious and costly and are being replaced by more precise and quantitative processes which enable the rapid, low cost production of patient-specific prostheses. In this two part review, we provide a comprehensive report of past, present and emerging soft-tissue prosthetic materials and manufacturing techniques. In this review, part A, we examine, historically, the ideal properts of a polymeric material when applied in soft-tissue prosthetics. We also detail new research approaches to target specific tissues which commonly require aesthetic restoration (e.g. ear, nose and eyes) and discuss both traditional and advanced fabrication methods, from hand-crafted impression based approaches to advanced manufactured prosthetics. We discuss the chemistry and related details of most significant synthetic polymers used in soft-tissue prosthetics in Part B. As advanced manufacturing transitions from research into practice, the five millennia history of prosthetics enters a new age of economic, personalized, advanced soft tissue prosthetics and with this comes significantly improved quality of life for the people affected by tissue loss.

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Advancements in Soft-Tissue Prosthetics Part A: The Art of Imitating Life

Purpose Three-dimensional (3D) facial scanning is an emerging clinical tool to capture external anatomical features for quantitative assessment and treatment in a wide range of clinical settings. Materials and methods In this study, an economical approach for rapid scanning of faces in the clinic was developed and validated to record valuable 3D patient data using smartphone cameras and photogrammetry software. Five novice operators were recruited to watch an instructional video developed on the technique before scanning 20 healthy adult participants. Results The smartphone-based photogrammetry approach produced scans with 1.3 mm (± 0.3 mm) accuracy in comparison to a metrology-rated gold standard device and were 88% (±14%) complete, with no significant difference observed between operators. A moderate to strong intrarater reliability was determined for all novice operators, suggesting that first-use operators can capture consistent scans based on watching an instructional video. Conclusion Smartphone photogrammetry could provide a rapid, non-invasive and economical method to capture patient morphological data for clinical assessment and personalized device manufacture. Inexperienced operators can quickly learn and utilize smartphone photogrammetry to provide accurate and reliable facial scans, essential for future clinical translation. This article is protected by copyright. All rights reserved.

Maureen T. Ross

Papers

Design tools for patient specific and highly controlled melt electrowritten scaffolds

Past, Present, and Future of Soft-Tissue Prosthetics: Advanced Polymers and Advanced Manufacturing.

Aesthetic reconstruction of microtia: a review of current techniques and new 3D printing approaches

Advancements in Soft-Tissue Prosthetics Part A: The Art of Imitating Life

A Method for Economical Smartphone-Based Clinical 3D Facial Scanning.