Following high profile, life changing long term mental illnesses and fatalities in sports such as skiing, cricket and American football-sports injuries feature regularly in national and international news. A mismatch between equipment certification tests, user expectations and infield falls and collisions is thought to affect risk perception, increasing the prevalence and severity of injuries. Auxetic foams, structures and textiles have been suggested for application to sporting goods, particularly protective equipment, due to their unique form-fitting deformation and curvature, high energy absorption and high indentation resistance. The purpose of this critical review is to communicate how auxetics could be useful to sports equipment (with a focus on injury prevention), and clearly lay out the steps required to realise their expected benefits. Initial overviews of auxetic materials and sporting protective equipment are followed by a description of common auxetic materials and structures, and how to produce them in foams, textiles and Additively Manufactured structures. Beneficial characteristics, limitations and commercial prospects are discussed, leading to a consideration of possible further work required to realise potential uses (such as in personal protective equipment and highly conformable garments).

Value streams for collected post-consumer textiles continue be analyzed within the global challenge to develop and employ commercially viable, yet ethical and sustainable strategies within the fashion industry. Upcycling is an existing strategy applicable to fashion production, with discarded materials used to design and create higher value products, keeping them in productive use for longer. A number of very small, niche upcycling enterprises have emerged in the UK. These brands have succeeded in creating stylistically relevant and commercially successful fashion styles utilizing waste textile materials. The advantages of scaling these enterprises up are not only environmental, but also economic and social, thereby creating a sustainable and innovative business model for UK led fashion production. Due to high levels of three key metrics of carbon, water and waste, UK government agency WRAP (Waste & Resources Action Programme) has identified textile products as priority materials for reuse and recycling. Upcycling enables a sustainable design option for reuse techniques to be employed for greatest economic and environmental benefit, in which used clothing and textiles are sourced for the production of newly designed fashion products. This paper identifies the key differences between standard fashion design and production processes and upcycled fashion design and production processes, in order to aid the development of large-scale fashion upcycling in the UK, and contribute to a circular economy.

Silicone is a synthetic polymer widely used in the biomedical industry as implantable devices since 1940, owing to its excellent mechanical properties and biocompatibility. Silicone biomaterials are renowned for their biocompatibility due to their inert nature and hydrophobic surface. A timeline illustration shows critical development periods of using silicone in varied biomedical applications. In this review, silicone properties are discussed along with several biomedical applications, including medical inserts, speciality contact lenses, drains and shunts, urinary catheters, reconstructive gel fillers, craniofacial prosthesis, nerve conduits, and metatarsophalangeal joint implants. Silicones are prone to microbial infections when exposed and interactions with the host tissue. As in the case of medical inserts, the development of specific antimicrobial strategies is essential. The review highlights silicone implants' interaction with soft and bone tissue and various antimicrobial strategies, including surface coating, physical or chemical modifications, treating with antibiotics or plasma‐activated surfaces to develop the resistance to bacterial infection. Finally, 3D printing technology, tissue engineering, regenerative medicine applications, and future trends are also critically presented, indicating the silicone's potential as a biomaterial.

Poisson's ratio (ν) is the negative ratio of the lateral-to-axial strain of a material under compression or tension and ranges between À1 and þ0.5 for 3D isotropic materials, according to elasticity theory, [1] and À1 and þ1 for 2D isotropic materials. [2] Auxetic materials (and structures) have a negative Poisson's ratio (NPR) as they expand laterally when stretched and contract laterally when compressed. [3] Auxetics can have enhanced properties including increased resistance to indentation and increased energy absorption under compression. [4,5] They also exhibit synclastic curvature, [3,6] which could improve the conformability of clothing to the body. Such properties make auxetics ideal candidates for enhancing personal protective equipment (PPE) in sport, [7] such as those used in rugby, [8] American football, [9] or snow sports. [10] Head injuries, for example, still frequently occur in sport despite developments in helmet technology and increased user uptake. [11,12] Shear thickening materials are often used in sporting PPE products, such as snowboard back protectors, but their ability to limit impact forces can change with temperature. [13] Approximately 4.5 million people are treated in EU hospitals for sports-related injuries annually, [14] at a cost of €2.4 billion (%£2 billion), [15] which could be reduced with more effective protection and better regulation. Better fitting, more comfortable, and higher-performing auxetic PPE has the potential to increase participation in sport and improve general well-being, both physically and mentally. [16] In addition, a more active population could reduce healthcare costs, particularly as National Health Service providers spent %£900 million on addressing health issues related to physical inactivity in the UK in 2009/2010. [17] There are also social health benefits of practicing a sport with others. [18] Bailly et al. found that snow-sport participants with an injury that was not to the head were less likely to be wearing a helmet than those without an injury, [19] challenging the concerns of Wilson that sporting participants who wear PPE take more risks. [20] Although auxetic systems can be found in nature, [21] research into these materials has typically focused on manmade products like open-cell foam, which was first manufactured by Lakes using thermomechanical techniques that combined compression and heating. [3] Auxetic foam fabrication has also been investigated by Chan and Evans. [4,22] Scarpa et al. were the first to report the dynamic response of auxetic open-cell foam, highlighting its potential in crashworthiness applications. [23] More recently, this potential was demonstrated further; open-cell auxetic foam reduced the peak acceleration of drop tower impacts (energies up to 5.6 J) by two to three times, compared with its conventional

A finite element model of an impact test on a soft tissue simulant, used as part of a shoulder surrogate, was developed in Ansys© LS-DYNA®. The surrogate consisted of a metal hemicylindrical core, with a diameter of 75 mm, covered with a 15 mm thick relaxed muscle simulant. The muscle simulant consisted of a 14 mm thick layer of silicone covered with 1 mm thick chamois leather to represent skin. The material properties of the silicone were obtained via quasi-static compression testing (curve fit with hyperelastic models) and compressive stress relaxation testing (curve fit with a Prony series). Outputs of the finite element models were compared against experimental data from impact tests on the shoulder surrogate at energies of 4.9, 9.8 and 14.7 J. The accuracy of the finite element models was assessed using four parameters: peak impact force, maximum deformation, impact duration and impulse. A 5-parameter Mooney-Rivlin material model combined with a 2-term Prony series was found to be suitable for modelling the soft tissue simulant of the shoulder surrogate. This model had under 10% overall mean deviation from the experimental values for the four assessment parameters across the three impact energies. Overall, the model provided a repeatable test method that can be adapted to help predict injuries to skin tissue and the performance/efficacy of personal protective equipment.