Hartvigsen har hatt flere lengre forskningsopphold ved utenlandske universiteter: Department of Computer Science, University of Twente, Nederland (1994–95), Faculty of Medicine, Munich University of Technology(høst 2006), Center for Health and Technology, University of California Davis / UC Davis (2011-2012), ITACA, Technical University of Valencia (2017-2018), Health Informatics Centre, Karolinska Institutet, Stockholm (2021–2022) og Department of Health Science and Technology, Aalborg Universitet, Danmark (juni 2022).