Integrated sensing layer of bacterial cellulose and polyethyleneimine to achieve high sensitivity of ST-cut quartz surface acoustic wave formaldehyde gas sensor.

•A highly sensitive formaldehyde gas sensor was developed based on ST-cut quartz surface acoustic waves (SAWs).•Bacterial cellulose are effective to enhance the sensitivity of polyethyleneimine to formaldehyde and reduce response time.•Key sensing mechanism is the mass loading effect caused by the reversible nucleophilic addition reaction.•The developed SAW sensor has good selectivity and stability.