# Microheater Topology for Advanced Gas Sensor Applications with Carbyne-Enriched Nanomaterials
## 3 Results
It can be noted that the time delay is greater with two orders of magnitude longer than for the case of small meander. When the sensor is heated for desorption, the density of the gas-sensing layer is altered, leading to a modification in its interaction with the SAW. This altered interaction could result in a greater time delay as the SAW propagates through the piezoelectric substrate and the modified gas-sensing layer. This phenomenon can be ascribed to changes in the acoustic impedance or the velocity of the SAW due to the modified surface properties following the desorption cycle. The deviation of \(\tau\) from the initial value was 18.7% at the beginning of the measurement for low concentrations, 35.7% at the end of the measurement for high concentrations, and an average of 25% in the range of 450-600 ppm (with no crossing in the whole range), where the sensor response is linear. The hysteresis is broader than the small meander case, and it can be concluded that there is a weaker degree of recovery in the sensor properties after desorption. The broader hysteresis loop in the high concentration range and the consistent deviation from the initial value could indicate that the gas-sensing layer undergoes non-reversible changes, possibly affecting the interaction between the gas molecules and the sensor surface. These changes in the surface interaction could lead to the observed broadened hysteresis and the non-linearity in the sensor response at higher concentrations. This behavior could be linked to phenomena such as saturation effects or changes in the surface chemistry of the sensor, affecting its response characteristics, which require additional investigation. At higher concentrations, the broader hysteresis loop may indicate that the desorption and re-sorption processes lead to more significant and slow changes in the sensor's surface properties. This can result in a slower recovery to the initial state, causing a broader hysteresis loop in the output transducer's time delay compared to the input transducer. Conversely, at lower concentrations, the narrower hysteresis loop may suggest that the desorption and re-sorption processes have less impact on the sensor's surface properties, leading to a faster and more complete recovery to its initial state. Further studies on the specific surface processes and interactions occurring during desorption and sorption cycles would be needed to elucidate the underlying scientific mechanisms fully  
The power consumption of the large meander microheater is 4.63 mW due to the 2.5-fold higher resistance of the large meander compared to the small one. Figure 5: Time delay and voltage attenuation of the sensor with the small meander topology (**a**) before activating the heater, (**b**) after activating the heater (desorption). Time delay and voltage attenuation of the sensor with the large meander topology (**c**) before activating the heater, (**d**) after activating the heater (desorption). Time delay and voltage attenuation of the sensor with the dense rectangular topology (**e**) before activating the heater, (**f**) after activating the heater (desorption). For the dense rectangular topology, it can be noted that the time delay is the highest among all three types of microheaters (Figure 6c), but with the same order of magnitude as for the large meander. The deviation of \(\tau\) from the initial value is 30% at the beginning of the measurement for low concentrations, 12.1% at the end of the measurement for high concentrations, and an average of 26% in the range of 450-600 ppm (with crossing at 500 ppm), where the sensor response is linear. The hysteresis is broader than in the small meander case, but narrower in the range of high concentrations than in the large meander case. The desorption rate for the rectangular microheater is 0.73 \(\upmu\)s/ppm vs. 0.33 \(\upmu\)s/ppm for the large meander and 0.03 \(\upmu\)s/ppm for the small meander.