Softness is based on a combination of structure and formulation, and currently available softest version is RealDoll UltraSoft 5.0 that contains customized silicone (Shore A hardness range of 00-10, 20-30 industry standard). Elastic modulus at chest level reaches down to 0.05MPa (on the border with 0.03-0.08MPa that adipose tissue in humans shows). Pressure test shows that the depression depth is 12mm under the 500Pa pressure (the normal silicone model is 5-8mm), the rebound time is 1.2 seconds (the actual skin is about 0.8 seconds), and the degree of simulation touch is increased to 94%. The three-year, $23 million model, which will account for 62% of the premium soft model market when it hits the roads in 2023, has material science breakthroughs.
It centers around Japanese firm EXDOLL’s HyperSilky V2, which uses nanoscale aerogel filling technology (98% porosity) to reduce silica gel density from 1.15g/cm³ to 0.68g/cm³, but still retain a tear strength of 5MPa (national standard minimum requirement of 1.5MPa). Dynamic mechanical analysis of the hip area showed loss factor (tanδ) of 0.12 at frequency of 10Hz, getting to the level of 0.08-0.15 for human soft tissue, and the error rate for tactile feedback was as low as 3%. However, this model comes with a price as high as 85,000 yuan because material cost is 220% more than in traditional products.
User employed measurement data to ascertain the softness. WM Doll’s PlushPro was third-party blind tested (sample population 1,200 individuals) and 83% of subjects rated its feel as “significantly better” than a live skin simulator (baseline measure ΔE < 1.5). The silicone formula in this model contains 12% liquid silicone oil (viscosity 350cSt), and the surface friction coefficient is 0.15 (dry) to 0.08 (wet), which is approaching the range of 0.2 to 0.3 human skin. However, maintenance is expensive and the special care oil of ￥600 needs to be applied every month to prevent leakage of silicone oil.
Technological advancements improve life and flexibility balance. Chinese company Jinsanrobot’s BioFlex 3.0 utilizes self-healing silica gel (92%/24 hours crack healing rate), Shore hardness level 00-15 adjustable, along with Mr Joint (5ms response time), to achieve pressure sensitivity of ±0.1N. Experimental results show that under 100,000 extrusion tests (50N/time pressure), the hip deformation rate is as low as 3% (15-20% of traditional models) while motor power consumption increases by 18W/h.
Economic analysis shows that the ultra-soft model is more costly in terms of maintenance. UltraSoft 5.0 annual care costs approximately ￥4,500 (￥1,200 for traditional models) because of the necessity of using the incubator (25±0.5 ° C) for 8 hours a week to avoid hardening. User research shows that despite its 3-5 times higher price than the base model ($98,000 vs. $25,000), it has a 41% repeat buy (industry average 12%) and a customer satisfaction NPS measure of 78.
Compliance to laws affects material choice. The EU REACH regulation requires VOC emissions of soft silica gel to be < 50μg/m³, resulting in a recall of 15,000 sets of non-compliant products (120μg/m³) by a manufacturer in 2022. Compliant versions such as Sinthetics’ CloudTouch, which is FDA 21 CFR 177.2600 certified, are selling points for their flame retardancy (self-extinguishing time < 2 seconds) and biodegradation rate (85% degradation in 5 years), but their UV resistance is compromised (color change period ΔE > 3 is reduced from 5 years to 2 years).
Severe cases reveal material limitations. In 2023, a user stored UltraSoft 5.0 at a -20℃ environment for 48 hours, causing the silicone hardness to rise from 10 to 45 (permanent damage), and the maintenance cost increased to 32,000 yuan. As a result, manufacturers launched intelligent temperature-control apparel (￥8,500/set), maintaining the surface temperature between 20-40℃ through the graphene heating film (power 25W), which reduced the likelihood of low-temperature embrittlement by 98%.
Emerging trends are bio-fusion materials. The rpsexdoll lab tests “living skin” with 30% collagen, which generates interest for its instant softness (Shaw level 00) and self-healing property (1mm incision healing /72 hours), but costs as much as $12,000 a month (requires a special nutrient solution). Its prototype, displayed at CES 2024, demonstrated dynamic vascular pattern changes under 50N pressure (response time 0.8 seconds), but after mass production, the power consumption was 45W (standard model 5W), and commercialization is still a challenge.