Under Your Skin Project Report

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<ul><li><p>markwilsons157386</p><p>imitations of life</p><p>underyourskin </p></li><li><p>Using our own microanatomy as </p><p>inspiration, Under Your Skin attempts to </p><p>artificially recreate capillary refill. It explores </p><p>manufacture methods and processes that </p><p>allow for an anatomically accurate simulation </p><p>of this physiological phenomenom.</p><p>projectstatement</p><p>contact | markwilsonnz33@gmail.comcoach | markthielenTU/e</p></li><li><p>The aim of this project is to create a product </p><p>that could be used in medical training </p><p>scenarios. It looks at product systems </p><p>and services surrounding existing medical </p><p>simulation products and attempts to find </p><p>ways to design or redesign aspects to </p><p>ultimately improve the effectiveness of </p><p>medical simulation training.</p><p>introduction</p></li><li><p>Medical simulation is used as a method of </p><p>education for training health professionals </p><p>in their various medical fields. Its main </p><p>purpose is to reduce the number of </p><p>accidents that could occur in patient </p><p>diagnosis, surgery, prescription, or </p><p>general practice.</p><p>It is important that products used in </p><p>medical simulation succeed in creating </p><p>an experience that is as realistic as </p><p>possible. The more life-like and realistic </p><p>the experience is, the more effective and </p><p>valuable the training becomes.</p><p>Currently, there are very few products that </p><p>convincingly simulate capillary refill. They </p><p>lack realism, consequentially hindering </p><p>the sense of realism simulation products </p><p>aim to achieve.</p><p>medicalsimulation</p></li><li><p>Capillaries are the smallest blood vessels in </p><p>our body. When our skin in pressed, blood </p><p>is squeezed from these vessels and, due </p><p>to circulation, this blood is restored. This </p><p>phenomenon is called capillary refill. It is </p><p>seen as a change of colour in the surface </p><p>of your skin generally from yellow/white </p><p>to red/purple. Our bodys circulation can </p><p>be easily affected by our physiological or </p><p>pathological. By observing the capillary </p><p>refill time (CRT) health professionals </p><p>are able to make quick assessments of </p><p>this condition using no equipment. For </p><p>example, a person who has lower blood </p><p>pressure will have a higher CRT once their </p><p>skin is pressed.</p><p>This type of test is commonly conducted </p><p>during neonatal examinations. A small </p><p>amount of pressure is applied to the </p><p>sternum, forehead, or ankle for five </p><p>seconds, and the CRT is observed. The </p><p>test conductor is then able to quickly </p><p>assess the general health of the baby.</p><p>capil laryrefill</p></li><li><p>After exploring existing products that simulate </p><p>capillary refill, it was quickly apparent that </p><p>the lack of realism needed to be addressed. </p><p>The products adopted various techniques </p><p>such as RGB LEDs to simulate a change in </p><p>skin colour. Fake hard-plastic bodies with </p><p>glowing chests left a lot to the imagination, </p><p>detracting from what is supposed to be a </p><p>realistic experience.</p><p>existingproducts</p></li><li><p>Inspiration for this project was taken from our </p><p>own bodies. Through examining the systems and </p><p>mechanisms within skin, and by observing it from </p><p>a sensory perspective, we are able to build an </p><p>understanding and knowledgebase to design with. </p><p>Using this knowledge, we will be able to produce </p><p>the most life-like simulation products.</p><p>designinfluence</p></li><li><p>The skin is the largest organ of your </p><p>body. Its primary functions include </p><p>providing protection against invasions of </p><p>microorganisms and regulation of body </p><p>temperature. Skin itself is fundamentally </p><p>comprised of three layers: the epidermis, </p><p>the dermis, and the subcutis. The </p><p>epidermis is the outer most layer of skin, </p><p>providing a waterproof barrier and the </p><p>colour of our skin tone. The average </p><p>thickness of this layer ranges between </p><p>0.05mm over our eyelids, to 1.5mm on </p><p>the soles of our feet and palms on our </p><p>hands. The dermis contains various </p><p>tissues and structures such as connective </p><p>tissue, hair follicles, sweat glands, and </p><p>capillaries. The thickness of this layer </p><p>ranges between 0.3mm at our eyelids, to </p><p>3.0mm on our backs. The deepest layer of </p><p>skin is called the subcutis or hypodermis. </p><p>It is comprised of connective tissue and </p><p>fat cells.</p><p>anatomy</p></li><li><p>Its the blood vessels and capillaries in your </p><p>dermis that are squeezed and emptied </p><p>when pressure it applied to your skin. </p><p>The lack of blood creates a yellow/white </p><p>spot where pressure was, which quickly </p><p>refills depending on your various factors. </p><p>The upper normal limit for refill time in </p><p>newborns is 2 seconds. A prolonged refill </p><p>time can indicate various health issues </p><p>such as shock or dehydration. The longer </p><p>the time taken for capillaries to be refilled, </p><p>the more serious the state of health can </p><p>be assumed.</p><p>capil laries</p></li><li><p>In order for products that simulate skin </p><p>to achieve suspense of disbelief, they </p><p>must replicate qualities of real human </p><p>skin. These qualities can be defined and </p><p>categorised as sensory relationships we </p><p>have with our skin. There are only two </p><p>senses used in observing capillary refill </p><p>time: sight and touch. By observing skin </p><p>visually, we recognise it by its colour and </p><p>surface texture including small details </p><p>such as wrinkles, hairs, or pores. We </p><p>can detect what part of the body areas </p><p>of skin is by observing its shape and </p><p>contours, which is determined by what </p><p>lies underneath it (bones, organs, etc.). </p><p>By observing the tactility of skin through </p><p>touch, we can feel what lies beneath it </p><p>and we can estimate how thick it might </p><p>be. We can detect the temperature, and </p><p>the softness and elasticity as it reacts to </p><p>our touch. Its colour changes when we </p><p>apply and release pressure. All of these </p><p>factors and qualities make skin both </p><p>dynamic and static, making it very difficult </p><p>to simulate.</p><p>sensoryobservation</p></li><li><p>It are these intrinsic qualities of skin that can be implemented </p><p>to induce suspense of disbelief. They are key to providing </p><p>an effective empirical experience through a mirror of reality.</p></li><li><p>Microfluidics defined as the study of </p><p>flows that are simple or complex, mono </p><p>or multiphasic, which are circulating in </p><p>artificial microsystems. I briefly explored </p><p>microfluidic mechanics in an attempt </p><p>to discover methods or systems I could </p><p>design with.</p><p>I learnt about a method using a silicone </p><p>called polydimethylsiloxane. This type of </p><p>material could be treated with plasma to </p><p>make it hydrophilic or hydrophobic. This </p><p>means that artificial capillary action such </p><p>as self-filling capillaries could be created </p><p>using microfluidic mechanics. However, </p><p>although it was possible to create idyllic </p><p>micro-channels, fabrication methods </p><p>required relatively advanced machines. I </p><p>instead decided to move on to exploring </p><p>fluidic behaviours for myself by observing </p><p>trial-and-error iterations with manageable </p><p>fabrication techniques.</p><p>microfluidics</p></li><li><p>Using my new understanding of the </p><p>sensory and mechanical properties of </p><p>skin, I began to think about how I could </p><p>create artificial capillary systems and </p><p>mechanisms. I explored materials and </p><p>their aesthetic and tactile properties, and </p><p>thought of ways I could create products </p><p>that closely mimicked our own anatomy. </p><p>I first looked at comparisons between </p><p>human skin and artificial materials by </p><p>using the Shore scale. This is a scale </p><p>determined using a Shore durometer - a </p><p>small instrument designed to measure </p><p>the hardness of polymers, elastomers, </p><p>and rubbers. Human skin has a Shore </p><p>hardness of about 0 15 on the Shore A </p><p>Scale. I was able to then identify materials </p><p>with similar Shore hardnesses that could </p><p>be used as a starting point for my project. </p><p>Two materials interested me. These were </p><p>TangoPlus and silicone. Because these </p><p>materials are used and manufactured in </p><p>two very different ways, I needed to make </p><p>two clear directions in order to explore </p><p>both.</p><p>concept</p></li><li><p>TangoPlus is used in high-resolution 3D </p><p>printers such as the Connex2. It is a rubber-</p><p>like material that can be fused with varying </p><p>amounts of Vero (another material) to print </p><p>a combine material of any Shore hardness </p><p>value between Scale A 26 and Scale D 86. </p><p>The closest Shore hardness value to skin </p><p>is that of pure TangoPlus, which has an A </p><p>Shore hardness of around 26 28. Pure </p><p>TangoPlus has great elasticity, flexibility, and </p><p>strength, enabling it to be stretched to just </p><p>over two times its length before tearing. It </p><p>is printed clear, but can be coloured using </p><p>pigments or dyes.</p><p>tangoplus</p></li><li><p>Using 3D printing as a method to </p><p>create capillaries has advantages and </p><p>disadvantages. Developments in 3D </p><p>printing technology has allowed for higher </p><p>resolution - and therefore higher detailed </p><p>- prints. I wanted to see how small I could </p><p>create channels to use as capillaries. </p><p>Some printers today can print as small </p><p>as 16microns. The elasticity and freedom </p><p>with form appealed to me, as I would </p><p>be able to rapidly prototype channels </p><p>to explore fluidic behaviour across </p><p>varying compositions, scales, and Shore </p><p>hardness values.</p><p>However, I knew 3D printing has its </p><p>limitations. When printing, a support </p><p>material is used to fill the channels in </p><p>order to lay the TangoPlus down onto </p><p>something before it is cured. This support </p><p>material needs to then be removed after </p><p>printing. This can sometimes be difficult, </p><p>depending on the complexity and size of </p><p>the channels. Limitations of 3D printing is </p><p>very much dependent on the designers </p><p>level of skill with computer-aided design </p><p>software. It is also very expensive.</p></li><li><p>Silicone is a rubber-like material that can </p><p>come in a large variety of Shore hardness </p><p>values from Shore A 00 and upwards. It </p><p>is relatively easy to work with due to its </p><p>flexibility, strength, and ability to be cast </p><p>and moulded. Silicones can also be easily </p><p>coloured using pigments and dyes. These </p><p>factors make it an ideal material to imitate </p><p>human skin.</p><p>Moulding silicone is a relatively easy </p><p>manufacturing method. It cures as a thick </p><p>liquid around any object or mould, picking </p><p>up even the smallest surface textures. </p><p>The level of detail that can be achieved </p><p>with silicone moulding appealed to me. I </p><p>wanted to see how small I could mould </p><p>channels.</p><p>Moulding silicone has a lot of limitations, </p><p>too. The composition of the channels </p><p>would be limited by the manufacturing </p><p>technique. Silicone is also expensive.</p><p>si l icone</p></li><li><p>After numerous sketch-explorations of </p><p>composition, channel size, and layering, </p><p>I designed three small models that I </p><p>would 3D print. Each print would be used </p><p>to demonstrate different properties of </p><p>TangoPlus that I wanted to intentionally </p><p>exploit.</p><p>1 Multi-layered patterningI designed this print to test the behaviour </p><p>of fluid within 1mm channels when </p><p>pressed. By having two layers of tight-knit </p><p>patterns, I was able to demonstrate how </p><p>fluid could be pushed around within the </p><p>channels. On one of the layers I included </p><p>multiple entrances to the pattern to see </p><p>if a change in pressure would affect the </p><p>behaviour of the fluid. The additional </p><p>entrances increased the distribution of </p><p>the fluid when pushing it through the </p><p>channels. They also made the removal </p><p>of the support material from within the </p><p>structure easier.</p><p>3dprints</p></li><li><p>2 CavitiesMy second sample model is designed with </p><p>two cavities that could be filled with fluid. </p><p>These cavities are joined using three small </p><p>channels. The aim of this design was to </p><p>see if a thin layer of TangoPlus would be </p><p>soft enough to push fluid through to the </p><p>second cavity, and whether it had enough </p><p>tensile strength to pull any fluid back </p><p>through when the structure was sealed </p><p>off. This proved semi-successful. A 2mm </p><p>layer of TangoPlus was soft enough to </p><p>easily push fluid through 1mm channels. </p><p>However, when sealed, the material was </p><p>not strong enough to pull the fluid back </p><p>through.</p><p>3 Back and ForthThe third sample model was designed </p><p>to see how fluid behaved in varying sizes </p><p>of channels. I wanted to see how thin I </p><p>could get the channels. This model took </p><p>the longest to remove all the support </p><p>material as it was difficult to reach the </p><p>support material trapped at the centre of </p><p>the model. </p></li><li><p>I began exploring with silicone by testing </p><p>different brands, mix types, and Shore </p><p>hardness values. I quickly found that </p><p>silicone quality was important. A lot of </p><p>the cheaper products were 10:1 mixes. </p><p>Even at a relatively low Shore A hardness </p><p>of 20, these silicones were not ideal to </p><p>use as artificial skin. Although they were </p><p>quite strong, they often cured far too hard </p><p>and didnt possess softness similar to </p><p>skin. They also often sweated, leaking </p><p>moisture and oils.</p><p>The best and most realistic silicones were </p><p>from the 1:1 Smooth-On range. Smooth-</p><p>On Dragon Skin and Smooth-On EcoFlex </p><p>20 provided the most realistic artificial </p><p>skin samples. Dragon Skin was strong </p><p>enough to withstand a considerable </p><p>amount of force and was therefore highly </p><p>elastic. EcoFlex 20 was soft and could be </p><p>compressed easily. It felt most like skin </p><p>tissue and would therefore be perfect for </p><p>simulating human skin.</p><p>si l iconemoulding</p></li><li><p>I briefly experimented with layering these </p><p>two silicones. A thin layer of Dragon Skin </p><p>on top of a thicker layer of EcoFlex 20 </p><p>acted in a very similar way to our own </p><p>skin the epidermis and the dermis. This </p><p>led me to the next stage of my process: </p><p>moulding.</p><p>Silicone can pick up extraordinary detail </p><p>whilst retaining the form in which it cures. </p><p>I experimented with moulding silicone </p><p>around varying thicknesses and different </p><p>types of strings, suspending them in </p><p>a shallow dish. I quickly found nylon </p><p>thread to be easiest to work with due </p><p>to its consistent surface. It left perfectly </p><p>smooth and consistent channels inside </p><p>the silicone, and were easy to remove </p><p>without damaging the structure.</p></li><li><p>From here, I developed a method to </p><p>suspend rows of nylon thread evenly </p><p>across a thin sample patch of clear </p><p>silicone. This thread was 0.25mm thin. </p><p>Once the silicone cured and the nylon </p><p>thread was removed, I was able to fill the </p><p>channels with red dye. I could observe </p><p>the behaviour of the fluid within these </p><p>channels when the silicone was pressed </p><p>in different ways. Interestingly, the fluid </p><p>was visibly displaced beneath applied </p><p>pressure, and instantly refilled once it was </p><p>removed. I could recognise potential to </p><p>include mechanical or intelligent systems </p><p>to control the refill time of these channels.</p></li><li><p>Although the refill time of these channels </p><p>cannot yet be controlled, the realistic tactile </p><p>and visual qualities of this type of patch are </p><p>highly effective. This is believed to be the first </p><p>time a product that simulates the change </p><p>of colour in skin using moulded micro-</p><p>channels when pressure is applied has been </p><p>produced.</p><p>f inalproduct</p></li><li><p>The next step to this project would be to </p><p>finalise these silicone patches. Although </p><p>systems to control the time it takes for </p><p>fluid to refill the channels once they have </p><p>been pressed would be essential for a </p><p>product that simulates capillary refill, it </p><p>is as equally important that the silicone </p><p>patch achieves the suspense of disbelief </p><p>through its skin-like qualities.</p><p>The control of refill time has the potential </p><p>to be achieved using mechanical and </p><p>intelligent actuators. This could involve a </p><p>pressure sensor beneath the patch, and </p><p>an adjustable fader that could control </p><p>a small machine to restrict the flow of </p><p>fluid t...</p></li></ul>