Influence of environment on wetting properties of common polymers for Skin-Device Interfaces

Many non-invasive personal healthcare devices suffer from poor, occlusive skin contact. This disrupts physiological interface microclimate and device functionality. Surface engineering can provide multifunctional surfaces which precisely control and regulate microclimates at the skin-device interface. The regulation efficacy through surface engineering is contingent upon both the material and intrinsic surface properties, as well as the topology design. In particular, the wettability plays a crucial role in regulating these microclimate conditions. Before introducing surface engineering for developing innovative skin-device interfaces, the wetting behaviour of the materials needs to be determined. The polymeric materials polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE) are commonly used in non-invasive personal healthcare devices. Existing studies indicate an impact of temperature and relative humidity (RH) on the wetting properties, as characterised by the contact angle (CA). Nevertheless, most studies have been conducted under ambient conditions (20°C and 50% RH), on different materials, or are in disagreement regarding the climate dependence of polymer wettability. This study applies advanced characterisation and evaluation methods to set a reference for the wetting behaviour of the mentioned polymers in their untreated state. A custom climate chamber was designed and built in which temperature and humidity can be separately controlled. In this chamber, droplets can be applied on a surface, after which the CA can be measured using a goniometer. In this controlled environment, the CA of PP, PVC, PE and PDMS substrates was determined as a function of relative humidity (RH 10 to 90%) and temperature (5 to 50°C). The systematic and comprehensive study shows that although the CA is significantly different for almost all polymers, there is no significant dependence of the CA on either humidity or temperature for PP, PVC and PE. The water CA of PDMS exhibits a linear temperature dependency at a constant RH, while the CA measured with diiodomethane suggests a linearly inverse dependence on RH. We conclude that the influence of these climate conditions on the wettability of these polymers is negligible. For improvement of the device- skin interface we will therefore focus on engineering surface engineering strategies for microclimate regulation.Many non-invasive personal healthcare devices suffer from poor, occlusive skin contact. This disrupts physiological interface microclimate and device functionality. Surface engineering can provide multifunctional surfaces which precisely control and regulate microclimates at the skin-device interface. The regulation efficacy through surface engineering is contingent upon both the material and intrinsic surface properties, as well as the topology design. In particular, the wettability plays a crucial role in regulating these microclimate conditions. Before introducing surface engineering for developing innovative skin-device interfaces, the wetting behaviour of the materials needs to be determined. The polymeric materials polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE) are commonly used in non-invasive personal healthcare devices. Existing studies indicate an impact of temperature and relative humidity (RH) on the wetting properties, as characterised by the contact angle (CA). Nevertheless, most studies have been conducted under ambient conditions (20°C and 50% RH), on different materials, or are in disagreement regarding the climate dependence of polymer wettability. This study applies advanced characterisation and evaluation methods to set a reference for the wetting behaviour of the mentioned polymers in their untreated state. A custom climate chamber was designed and built in which temperature and humidity can be separately controlled. In this chamber, droplets can be applied on a surface, after which the CA can be measured using a goniometer. In this controlled environment, the CA of PP, PVC, PE and PDMS substrates was determined as a function of relative humidity (RH 10 to 90%) and temperature (5 to 50°C). The systematic and comprehensive study shows that although the CA is significantly different for almost all polymers, there is no significant dependence of the CA on either humidity or temperature for PP, PVC and PE. The water CA of PDMS exhibits a linear temperature dependency at a constant RH, while the CA measured with diiodomethane suggests a linearly inverse dependence on RH. We conclude that the influence of these climate conditions on the wettability of these polymers is negligible. For improvement of the device- skin interface we will therefore focus on engineering surface engineering strategies for microclimate regulation.Many non-invasive personal healthcare devices suffer from poor, occlusive skin contact. This disrupts physiological interface microclimate and device functionality. Surface engineering can provide multifunctional surfaces which precisely control and regulate microclimates at the skin-device interface. The regulation efficacy through surface engineering is contingent upon both the material and intrinsic surface properties, as well as the topology design. In particular, the wettability plays a crucial role in regulating these microclimate conditions. Before introducing surface engineering for developing innovative skin-device interfaces, the wetting behaviour of the materials needs to be determined. The polymeric materials polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE) are commonly used in non-invasive personal healthcare devices. Existing studies indicate an impact of temperature and relative humidity (RH) on the wetting properties, as characterised by the contact angle (CA). Nevertheless, most studies have been conducted under ambient conditions (20°C and 50% RH), on different materials, or are in disagreement regarding the climate dependence of polymer wettability. This study applies advanced characterisation and evaluation methods to set a reference for the wetting behaviour of the mentioned polymers in their untreated state. A custom climate chamber was designed and built in which temperature and humidity can be separately controlled. In this chamber, droplets can be applied on a surface, after which the CA can be measured using a goniometer. In this controlled environment, the CA of PP, PVC, PE and PDMS substrates was determined as a function of relative humidity (RH 10 to 90%) and temperature (5 to 50°C). The systematic and comprehensive study shows that although the CA is significantly different for almost all polymers, there is no significant dependence of the CA on either humidity or temperature for PP, PVC and PE. The water CA of PDMS exhibits a linear temperature dependency at a constant RH, while the CA measured with diiodomethane suggests a linearly inverse dependence on RH. We conclude that the influence of these climate conditions on the wettability of these polymers is negligible. For improvement of the device- skin interface we will therefore focus on engineering surface engineering strategies for microclimate regulation.Many non-invasive personal healthcare devices suffer from poor, occlusive skin contact. This disrupts physiological interface microclimate and device functionality. Surface engineering can provide multifunctional surfaces which precisely control and regulate microclimates at the skin-device interface. The regulation efficacy through surface engineering is contingent upon both the material and intrinsic surface properties, as well as the topology design. In particular, the wettability plays a crucial role in regulating these microclimate conditions. Before introducing surface engineering for developing innovative skin-device interfaces, the wetting behaviour of the materials needs to be determined. The polymeric materials polydimethylsiloxane (PDMS), polyvinyl chloride (PVC), polypropylene (PP), and polyethylene (PE) are commonly used in non-invasive personal healthcare devices. Existing studies indicate an impact of temperature and relative humidity (RH) on the wetting properties, as characterised by the contact angle (CA). Nevertheless, most studies have been conducted under ambient conditions (20°C and 50% RH), on different materials, or are in disagreement regarding the climate dependence of polymer wettability. This study applies advanced characterisation and evaluation methods to set a reference for the wetting behaviour of the mentioned polymers in their untreated state. A custom climate chamber was designed and built in which temperature and humidity can be separately controlled. In this chamber, droplets can be applied on a surface, after which the CA can be measured using a goniometer. In this controlled environment, the CA of PP, PVC, PE and PDMS substrates was determined as a function of relative humidity (RH 10 to 90%) and temperature (5 to 50°C). The systematic and comprehensive study shows that although the CA is significantly different for almost all polymers, there is no significant dependence of the CA on either humidity or temperature for PP, PVC and PE. The water CA of PDMS exhibits a linear temperature dependency at a constant RH, while the CA measured with diiodomethane suggests a linearly inverse dependence on RH. We conclude that the influence of these climate conditions on the wettability of these polymers is negligible. For improvement of the device- skin interface we will therefore focus on engineering surface engineering strategies for microclimate regulation.