Smart medical stocking using memory polymer for chronic venous disorders

TL;DR: This work aims to investigate and design a smart compression stocking using shape-memory polymer that allows externally controlling the pressure level in the wrapped position on the leg using external heat stimuli.

About: This article is published in Biomaterials.The article was published on 2016-01-01 and is currently open access. It has received 56 citations till now.

Summary

Summary

• Social inclusion, an essential element in the process of making friends, is recognised as a basic human right in the United Nations Convention on the Rights of Persons with Disabilities (United Nations General Assembly, 2006) in Article 19 on ‘Living independently and being included in the community’ and Article 30 on ‘Participation in cultural life, recreation, leisure and sport’.
• For people with access to the internet and with online skills, this has enabled a wider group of social contacts beyond those typically limited by geographical boundaries.
• Social exclusion and loneliness remain serious issues for people with a learning disability and much more needs to be done to realise their right to a full life in the community.
• This article suggests that specific support should be targeted to overcome the barriers identified above that prevent people living full and safe lives in their communities.
• Journal of Applied Research in Intellectual Disabilities, 17, 191-197.
• In Community; Practical lessons in supporting isolated people to be part of community, Stockport: HSA Press.

Figures

Fig. 2 – DMA results of the SMPU filament.

Fig. 1: Nonlinear relation between pressure and stocking circumference.

Table 1. Details of the stocking.

Fig. 5 – Pressure variation at different levels of strains (T= 40ºC).

Fig. 4 – (a) Pressure variation at different levels of temperature (13% strain). (b) Comparison with theoretical prediction using Eq. (7).

Fig. 6 – Pressure variation over time at different levels of strain and temperature. (a) Top -low strain level 5.85%, (b) Bottom - high strain level 20.27%.

Fig. 7 – Pressure variation during sequential heating and cooling of the stocking up to 5 cycles (C1-C5: individual cycles). Each cycle includes heating of the stocking for 30 min in heated chamber (T = 40ºC), and then cooling down for another 30 min at room temperature (T = 23ºC).

Fig. 3 – Set-up for pressure measurement

Table 2. Maximum recovery stress Δσ (104 Pa) generated by the stocking upon activation at different levels of temperature and strain

Table 3. Maximum level of extra pressure ΔP (in mmHg) generated by the stocking upon activation at different levels of temperature and strain

Frequently asked questions

Q1. What have the authors contributed in "Smart medical stocking using memory polymer for chronic venous disorders" ?

This work aims to investigate and design a smart compression stocking using shape-memory polymer that allows externally controlling the pressure level in the wrapped position on the leg. The authors then presented a case where such a stocking is developed using a blend yarn consists of selected shape-memory polyurethane and nylon filaments. 

Q2. What are the future works mentioned in the paper "Smart medical stocking using memory polymer for chronic venous disorders" ?

Future work in SMP should be done to examine several other factors, e. g., different SMPs, hard segment content, etc. 

Q3. Why can't a stocking be easily developed?

Because of the internal stress and heat stimuli connection of SMPU materials,stockings with massage effect can be easily developed if a programmed heating source is incorporated into the system. 

Q4. What is the key to achieving a desired pressure level?

If the authors can find a material whose internal stress σ can be easily adjusted in such that it can compensate the deviations of thepressure from the initially designated level, the authors can then sustain the desired pressure on the leg. 

Q5. What is the effect of the stocking on the pressure drop?

On activating the stocking at greater temperature, the pressure increases to a higher level for the initial period (10 min), and thereafter starts decreasing. 

Q6. What is the way to use a rubber stocking?

To sum up, the authors need a polymer material:1.   whose mechanical properties are sensitive enough to temperature changes of a narrowrange above the human body temperature;   8  2.   It obeys the rubber elasticity theories and, more specifically, follows Eqs. 5c or 6:during use of the stocking, an increase in temperature ΔT will lead to a sufficient increase in internal stress Δσ - hence a, b >0, and parameter b is sufficiently large; 3.   Also the selected material should be easy to process into stockings and comfort towear in contact with skin. 

Q7. What is the main reason why the use of SMP film actuators is not a viable?

The use of SMP film actuators may significantly obstruct the moisture transmission and the permeability of the compression system, and therefore not a viable solution for providing improved comfort to the patients. 

Q8. What is the effect of the stress on the internal stress in a stretched SMPU?

On the other hand, the internal stress in a stretched SMPU under constraint is caused by the entropic elasticity that will facilitate thermal contraction at high temperature. 

Q9. What are the main reasons for the poor quality of life?

Patients suffering from chronic venous disorders, such as leg ulcers, oedema, venousstasis, venous hypertension, etc., are known to have poor quality of life due to continuous discomfort or pain, limited mobility and long recovery time, in addition to a rigorous management plan and thus the financial cost involved [1, 2]. 

Q10. Why did SMPU filaments show a range of transition temperature?

SMPU filaments had shown a range of transition temperature (Fig. 3) due to the fact that not all the switching segments would activate altogether at a fixed temperature point. 

Q11. What is the effect of temperature on the pressure of the stocking?

Table 3 shows that the stocking is able to generate extra pressure up to maximum of 16.2 mmHg by selecting suitable level of temperature and strain. 

Q12. What is the relationship between the pressure and the recovery stress?

Correlation of extra pressure and recovery stress   15  As suggested by Laplace’s law (or Eq. 7), the interface pressure depends on theinternal tension or stress developed in the stocking in the wrapped position. 

Q13. What is the tensile strain in the stocking?

Once the stocking is applied to the leg, a tensile strain in the stocking, ε , is generated and can be calculated as,l s s C C C ε −= (1)Where lC and sC are the original circumferences of the leg and the stocking, respectively, and l sC C> .