INVESTIGATION OF SKIN LACERATION THRESHOLD UNDER A SPECIFIC CONDITION: BLADE PENETRATION TEST ON PORCINE SKIN

Skin lacerations are not fatal but constitute one of the most common injuries in daily life. There is a need, therefore, for measures to prevent skin lacerations caused by accidents; however, since only a few engineering studies have been undertaken, the threshold of skin laceration is still unclear. In this study, the thresholds of skin laceration under moderate loading rate are proposed according to the results of penetration tests on porcine skin using a knife or blunt blade. In the tests, a sharp blade (knife) and blunt blade with an edge having a small radius of curvature were applied to the external surfaces of dorsal and ventral porcine skin specimens. Penetration tests using sharp blades showed that the average rupture load was 39.0[Formula: see text]N for dorsal skin and 36.0[Formula: see text]N for ventral skin. On the other hand, the results of the penetration tests using the blunt blade were statistically analyzed by ordinal logistic regression, because the rupture load could not be defined precisely based on the load sequence data. The regression curves show that the rupture loads for a 50% probability were within the range of 123.7[Formula: see text]N to 214.4[Formula: see text]N for dorsal region skin and 80.1[Formula: see text]N to 160.0[Formula: see text]N for ventral region skin.

ANALYTICAL SOLUTIONS IN THE MODELING OF THE LOCAL RF ABLATION

Coupled mathematical models for the radiofrequency (RF) ablation performed in biomedical sciences have been developed based on the bioheat transfer theory. The heat exchange problem is important to be analytically studied in order to control the size of the necrosis zone caused by RF ablation. This lesion size in the tissue may be predicted by the knowledge of the internal tissue temperature. We propose an analytical solution for the Pennes heat transfer equation in bi- and tri-region domains, applicable to the RF ablation of cancerigeneous tissue — a clinical relevant problem. The model consists of two partial differential equations describing the spatio-temporal interactions between the electric and thermic effects. The aim is to find simple algebraic expressions of analytical solutions that may allow to generate quantitative results which in turn may be interpreted (including uncertainties). The dependence of the temperature as function of the electrothermal parameters in both diseased and surrounding healthy tissues is pointed out. Two cases, namely the tumor–tissue and tumor–tissue–skin systems, are graphically computed, and important findings include the fact that the presence of tissue with smaller value parameters protects somehow healthy cells. Moreover, the graphical representations are conducted to highlight the link of the profile of current density distribution in the physiological problem with the (neither oval nor circular) shape of the temperature isoclinic lines.

Prediction methods of skin burn for performance evaluation of thermal protective clothing

Most test methods use skin burn prediction to evaluate the thermal protective performance of clothing. In this paper, we reviewed different burn prediction methods used in clothing evaluation. The empirical criterion and the mathematical model were analyzed in detail as well as their relationship and limitations. Using an empirical criterion, the onset of skin burn is determined by the accumulated skin surface energy in certain periods. On the other hand, the mathematical model, which indicates denatured collagen, is more complex, which involves a heat transfer model and a burn model. Further studies should be conducted to examine the situations where the prediction methods are derived. New technologies may be used in the future to explore precise or suitable prediction methods for both flash fire tests and increasingly lower-intensity tests.

EFFICIENT DATA AND POWER TRANSFER FOR BIO-IMPLANTED DEVICES BASED ON ASK MODULATION TECHNIQUES

This paper presents a fully integrated system for implanted micro-system devices with efficient power and data transfer based on amplitude shift keying (ASK) modulation techniques. A proposed efficient class-E power amplifier is presented. The design presents a full transcutaneous inductive powering system to transfer power and data from an outside human body to implanted devices such as implanted microsystems to stimulate and monitor the nerves and muscles with low band frequency of 13.56 MHz according to the industrial–scientific–medical (ISM) band to avoid the tissue damage. A novel ASK demodulator powered with 1.9 V is proposed with a power recovery system. The modulation index is 13% and the modulation rate 7.3% with data rate 1 Mbit/s, and with power efficiency 66%. The system has been designed using 0.35-μm fabricated CMOS technology. The mathematical model is given and the design is simulated using OrCAD PSpice 16.2 software tool and for real-time simulation, the electronic workbench MULISIM 11 has been used to simulate the class-E power amplifier.

QUANTIFICATION AND THE UNDERLYING MECHANISM OF SKIN THERMAL DAMAGE: A REVIEW

Skin thermal damage is the most common thermal trauma in civilian and military communities. Besides, advances in laser, microwave, and similar technologies have led to recent developments of thermal treatments for diseases involving skin tissue aiming at inducing damage precisely within targeted tissue structures without affecting the surrounding healthy tissue. Pain sensation accompanying thermal damage is also a serious problem for burn patients. Therefore, it is of great importance to quantify the thermal damage in skin tissue. In this review, we detail the progress of the state-of-the-art mathematical models and experimental methods for the quantification of thermal damage (both heat damage and cold damage) and the general development of thermal treatments in tissue engineering. This could enable better understanding of the underlying mechanisms of skin thermal damage and the optimization of clinical thermal therapies.

A multi-scale view of skin thermal pain: from nociception to pain sensation

All biological bodies live in a thermal environment, including the human body, where skin is the interface with a protecting function. When the temperature is out of the normal physiological range, skin fails to protect, and the pain sensation is evoked. Furthermore, in medicine, with advances in laser, microwave and similar technologies, various thermal therapeutic methods have been widely used to cure disease/injury involving skin tissue. However, the corresponding problem of pain relief has limited further application and development of these thermal treatments. Skin thermal pain is induced through both direct (i.e. an increase/decrease in temperature) and indirect (e.g. thermomechanical and thermochemical) ways, and is governed by complicated thermomechanical-chemical-neurophysiological responses. However, a complete understanding of the underlying mechanisms is still far from clear. In this article, starting from an engineering perspective, we aim to recast the biological behaviour of skin in engineering system parlance. Then, by coupling the concepts of engineering with established methods in neuroscience, we attempt to establish multi-scale modelling of skin thermal pain through ion channel to pain sensation. The model takes into account skin morphological plausibility, the thermomechanical response of skin tissue and the biophysical and neurological mechanisms of pain sensation.

Strain rate sensitivity of skin tissue under thermomechanical loading

There have been limited studies addressing the thermally dependent mechanical properties of skin tissue, although this can contribute to a variety of medical applications. To address this, an experimental study on the tensile behaviour of pig skin tissue under different thermal loading conditions and different mechanical stretching rates was performed. The results indicate that there is a significant variation among skin tensile behaviours under different temperatures and loading rates, which is correlated with dermal collagen denaturation. The Ogden model was used to summarize the effect of the strain rate and the temperature upon the measured constitutive response through two parameters (alpha and mu). These results can be used in future models to improve clinical thermal treatments for skin tissue.