Science for Society: How a bracelet drives harassers away by spreading a sickening smell

Scientists work day in, day out to find solutions to a variety of problems. From new medicines to smart agricultural techniques; our research helps society move forward. But this is not always immediately visible. In the Science for Society section, we share stories about impactful innovations, products, and ideas to show that science works!

A truly sickening, disgusting smell to chase harassers away, activated by a small button on your bracelet: thousands of women all over the world already wear it to keep themselves safe. Sexologist Charmaine Borg of the Faculty of Behavioural and Social Sciences played a crucial role in its development.

Imagine this: a young woman leaves the club after a fun night of partying. Walking home, she hears footsteps behind her drawing closer and closer. Nobody else seems to be around. All of a sudden, an arm aggressively grabs her and tries to pull her into a dark alleyway. The woman presses a small button on her bracelet and an incredibly disgusting, aversive smell is released. The attacker is repulsed and can do nothing more than step away and retreat. Sounds like science-fiction? Not anymore.

What research lies behind this technology?

It all started with a question sexologist dr. Charmaine Borg and prof. dr. Peter de Jong had: ‘We found that feelings of disgust and sex are closely related and also contradictory. We found that, without any previous arousal, female test subjects react with disgust when shown sexual stimuli. However, this changes when women are already sexually aroused. Our conclusion: sexual arousal weakens women’s natural disgust response.’

The research gained a lot of attention. Borg was approached by innovator Roel van der Kamp, the founder of Invi. He had seen the statistics on sexual violence and was shocked at the numbers. Even though sexual violence comes in many forms and degrees of severity, he wanted to do something to provide some level of protection. Borg: ‘Reading our research, he wondered whether a disgusting smell could have a potential negative impact on sexual arousal. The other way around, so to say. My then supervisor and I already had a model in our minds where this could be true.’

Borg and her colleagues, inspired and encouraged by Van der Kamp, conducted a new study. Borg: ‘In this new research experiment, we let test subjects get an erection, after which one group would be given several puffs of a very aversive smell and the other a series of puffs of a neutral solvent. The smell that was used was created with chemistry professors and with American military experts that Roel came in contact with after the initial design of our study was completed. We discovered that this aversive smell alone, even when highly diluted, almost immediately kills the erection.’

How does the bracelet work?

The results gave both Borg and Van der Kamp the confidence that a bracelet that would spread an undiluted version of the aversive smell upon pressing a button could protect those wearing it. The Invi bracelet, available in different colours and styles, is worn like a regular bracelet. A button on a small metal canister releases the aversive smell, forcing those close by to take distance and alerting others further away to the fact that something is going on.

Used around the world

Van der Kamp is promoting the bracelet around the world, especially to women that have been sexually violated before. Borg: ‘Studies show that those women are more likely to be violated again. The bracelet gives them a certain confidence and feeling of safety they didn’t have before.’ The Dutch Sexual Assault Center now offers it to victims. NGOs in Burundi, Congo, and other places are doing the same. Over ten thousand bracelets have been sold so far.

Looking ahead, Borg envisions expanding this line of research to explore the broader psychological and physiological effects of wearing the bracelet. She has recently been in contact with Van der Kamp aiming to investigate whether it positively influences posture, self-perception, and assertiveness—factors that could contribute to reducing the risk of further victimization. Borg: ‘By integrating insights from psychophysiology and behavioural science, future studies could provide empirical evidence on how wearable interventions like the Invi bracelet enhance personal empowerment and resilience.’

Empowerment

Borg is happy about how it is going: ‘I was happy to be able to design a study that helped the development of the bracelet and, ultimately, the protection of women around the world. Of course, most types of sexual violence don’t occur in dark alleyways. However, it still provides some level of protection.’ Furthermore, those that wear the bracelet feel safer. Borg: ‘We often get emails from women who say that the bracelet has given them their confidence back, which is great. Actually, researchers in Rotterdam are now looking into the confidence the bracelet might give those who wear it. And we have heard stories of the bracelet being effectively used in non-sexual violent attacks as well, which is very promising.’

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