Conveying Sexual Tension in Writing

I am working on a short story about two physicists working together on a night shift; there is a heightened sexual attraction between them but they can't follow it through due to social awkwardness, and instead the experiment just goes to pot. It's a farcical romantic comedy, with a strong underlying sexual tension to carry it through.

After each draft, I re-read it and asked myself (and willing victims who volunteer to read my stuff) if the tension comes through. One of the earlier drafts it didn't, so I started to think about what makes sexual tension, and how can I put that down in a story effectively. I've managed to do it before in another story told from third person, so maybe it was a perspective thing, as this one is done in first person present.

These are my theories on making the sexual tension work in a story, to really draw you into the page. Maybe the story isn't quite there yet, but I have the ideas on how to do it.

Firstly it's about physical reactions and sensations. The way the body reacts to someone you are attracted to: shortness of breath, hair standing on end, heart rate increasing, shaking, flutters in the stomach. The main thing noticed in sexual attraction are your own physical sensations, how lust affects the body's responses. But it takes two for some sexy tension, and you can't see the heart beat of the other person or see if their stomach tingles, so the next ingredient is body language.

Body language says a lot about what we think and feel. When we are attracted to someone else, we pay a lot of attention to their body and motions. We become uber observant. So, I not only made my character be very aware of her own sensations, but also aware of the other character's body language, and inferring what his intentions are from it.

Thirdly, words. What the character's say to each other and how they say it tells us a lot about the situation, and dialogue is a good device to create tension. Effective dialogue shows us a lot. Dialogue, beats and gestures in a scene can be used effectively in a scene to up the tension, not only sexual tension.

Finally, an especially useful device if you are going for first person: emotions and fantasies. A way I managed to really get the sexual tension through was to throw my character's sexual fantasies during inappropriate moments. This is not only realistic, but making the character yearn and desire something helps the story go on and gives us tension because they want something so badly.

Writing sexual tension is fun! What other devices do you think would work?