Inclusive vibrotactile feedback design for touchscreen home appliances: optimising comfort and certainty across diverse user groups

Touchscreens have transformed digital interactions, but the absence of physical feedback may disadvantage users with reduced tactile sensitivity. This study investigates vibrotactile feedback for touchscreen home appliances to enhance comfort and certainty across young adults (18-55) and late middle-aged and older users (55+), highlighting inclusive design for multigenerational smart-home environments. Using a washing machine touchscreen , 32 participants experienced 28 vibration conditions varying in duration, intensity, and frequency. Mixed ANOVAs indicated significant main effects of all three parameters on certainty (all <i>p</i> < .05). Comfort ratings in the 18-55 group were influenced by intensity and frequency (both <i>p</i> < .05), while the 55+ group showed reduced parameter sensitivity. Settings around 100-200 ms, 0.55-0.70 g, and ∼230 Hz jointly maximised certainty and comfort across groups. This study demonstrates how parameters adjustments can optimise usability for late middle-aged and older users, fostering inclusivity in touchscreen interaction.