My research focus can best be described as ‘Beyond the Desktop’ Interaction Design. This concerns understanding how users interact with novel hybrid environments and designing such settings.

There's two parts to this: ‘Beyond the Desktop’ refers to systems that are not sitting on a desktop, not purely screen-based, that are integrated into physical environments, tangible, mobile, or wearable, taking on the form of large interactive displays that users interact with through movement, and that often address non-traditional domains (such as museums, outdoor work, games, etc.). Within this, Tangible Interaction has been at the core of my research pretty much from the beginning. Over time my interests broadened out to Ubiquitous Computing and anything that could be described as related to 'Embodied Interaction'.

Interaction Design refers to a focus on designing (or analysing) interaction that includes aesthetic aspects of the interaction experience as well as functional requirements and the embedding of systems in use situations. In terms of methods and approaches it favours iterative and explorative ways of working.

I am particularly interested in issues of social interaction and collaboration in these contexts. ‘Beyond the Desktop’ systems, which are often mobile, public or tangible, are considered a good candidate for supporting such kinds of social interaction. With my attention on how exactly interface design affords and structures these interactions my work tends to cross boundaries between HCI, CSCW and Interaction Design.

Non-Desktop Interaction in the Heritage and Museum Sector

Over the years I've come to work in several projects related to heritage and museums, specifically evaluating museum installations and thinking about novel ways to engage visitors to historic sites and museums. I've evaluated touchscreen as well as more non-traditional installations and am now moving into being more involved in system design.
 
Children and Technology

As I've been involved in several projects in educational areas, developing and testing applications for children, I might as well list this as one of my research areas, having come into this somewhat by coincidence. Children and families in addition are one of the main user groups in my museum research.

Methodical approach

Especially with novel technologies like UbiComp, we need to have a good understanding of the use context in order to create useful and usable systems. The challenges are often not so much in the technology, but rather in how to integrate it into existing practice or how to create novel practices that make use of the technology. We need to understand the application context as well as the new possibilities.

I guess I am pretty pragmatic and non-orthodox in my appropriation of methods, from User-Centered Design to more ethnographically influenced approaches, field studies, explorative prototyping, and engaging in Co-Design in partnership with users. I have done quite a lot of  'interaction analysis' of video data (as described by e.g. Jordan & Henderson), but also worked with interviews, group discussions, in-situ experiments with users, and integrated statistical data analysis of logfiles in some of my studies.

Further Research Interests 

As mentioned above, I have  a footing in Participatory Design or Co-Design, and have been on the Program Committee for the PDC conference several times as well as published there.

Some years ago, I collaborated with Peter Bittner (Humboldt University zu Berlin) on the question of professional responsibility in SC practice.
See:  Critical Computing 2005 paper A Micro-Ethical View On Computing Practice, IFIP'2002 paper "Responsibility and the Work of IT-Professionals"
Bittner, Hornecker, Twisselmann, Weber. Die berufliche Situation informatisch Handelnder in der ethischen Reflexion GI-Jahrestagung 2003.
I was part of the working group 'Responsibility' (Verantwortung) of the German Society of Informatics (GI ev) which rewrote the GI ethical guidelines
I am a member of the German sibling of CPSR (Computer Professionals for Social Responsibility), the FIfF and spent several years on its board.

My diploma theses investigated the didactics of teaching CS101 in informatics (CS) in Higher Education
(see  diploma thesis (1994, in german)  and  Programmieren als Handwerkszeug im ersten Semester(1998))