Hyung-Sik Kim

Thermal tissue ablation may damage surrounding healthy tissue and cause pain. In this study, tissue ablation with the sequential application of electrical energy-inducing irreversible electroporation (IRE) and electrolysis (EL) (IRE + EL = IREEL) was investigated. An IREEL device was designed to control five output pulse parameters: voltage level (VL), pulse width (PW), pulse interval (PI), pulse number (PN), and pulse tail time (PTT). IREEL experiments were conducted on vegetable tissue. The results indicated that by increasing the VL and PTT, the ablation area increased, whereas the impedance was reduced significantly. Almost no ablation area was observed when only EL or IRE at 500 V and 1000 V, respectively, were applied. The ablation area observed with IRE alone at 1500 V was defined as 100%. In the case of IREEL at 500 V and 1000 V, ablation was induced even with the use of micro-second level PTT, and ablation areas of 91% and 186% were achieved, respectively. For IREEL at a voltage of 1500 V, the ablation area expanded to 209% and the maximum temperature was 48.7 °C, whereas the temperature did not exceed 30 °C under other conditions. A change in pH was also observed in an agar-gel phantom experiment which was conducted to examine and confirm whether IREEL induced electrolysis. IREEL was able induce ablation at low voltages owing to the synergistic effect of applying IRE and EL sequentially. Moreover, the ablation areas at high voltages could be increased compared to the areas observed when IRE and EL were applied independently.

The purpose of this study is to analyze the cognitive characteristics that can be induced by vibration stimuli at two intensities, three frequencies, and five presentation periods. The experiment was conducted on 20 right-handed adult males, and a subjective evaluation was performed using a questionnaire. Regression analysis was performed to observe the parameters affecting cognitive characteristics according to changes in intensity, frequency, and stimulation duration. The regression analysis results showed that the cognitive characteristics affected by changes in intensity, frequency, and stimulation duration were “heavy”, “bold”, “thick”, and “light”. The cognitive characteristics affected by two-variable combinations were “deep”, “clear”, “vibrating”, “dense”, “numb”, “blunt”, “shallow”, “fuzzy”, and “soft”. Cognitive characteristics affected by either intensity, frequency, or stimulation duration were “fast”, “pungent”, “skinny”, “thin”, “slow”, “ticklish”, “tingling”, “prickling”, “tap”, and “rugged”. By observing the cognitive characteristics that can be induced by the combination of intensity, frequency, and stimulation duration, we confirmed that in addition to intensity and frequency, the stimulation duration is an important factor that influences the induction of various cognitive characteristics. The results presented in the study can be used to enhance the utility of haptic surfaces for extended reality applications.