Enhanced pH sensing with cholesteric liquid crystal-infused sodium alginate actuators

The schematic representation is showing the bending behavior of the SAA and CLC-SAA. The strip for pH 1 (acidic) and pH 14 (alkaline) on the left side. On the right side bending behavior of SAA and CLC-SAA for pH 7. [Display omitted] •Integrated sodium alginate hydrogel with cholesteric liquid crystal for pH sensing.•Extensively investigated the hydrogen bonding mechanism employed for pH sensing.•Demonstrates exceptionally quick bending responses in the millisecond range.•Highly adaptable for applications in soft robotics, the food industry, and various other fields. The present work developed a novel type of soft actuator capable of pH sensing, named CLC-SAA (Cholesteric Liquid Crystal-Infused Sodium Alginate Actuator). This actuator is created by combining sodium alginate hydrogel with cholesteric liquid crystal via an evaporation method. Our study validates the actuation mechanism by observing shifts in the vibrational stretching of carboxylic group bonds through FTIR spectroscopic investigations. Leveraging the weak acidic nature of carboxylic acid in sodium alginate hydrogel, this actuator offers distinct advantages. The CLC-SAA exhibits remarkably rapid bending responses, with fast responses observed of the order of 4 sec to 0.4 sec and bending angles as low as 3° to as high as 18°. This responsiveness is consistent across a wide range of pH values, making it highly adaptable and valuable for applications in medical, chemical, and bio-robotics fields. Such actuation holds significant promise for various applications due to its adaptability and wide-ranging capabilities.