OK, if the UV light is all absorbed by the plastic bottle then would an INTERIOR reflective layer be better? Perhaps the stainless water bottles REI sells may be the way to go. Anything that can increase the SteriPen's effectiveness would likely help us.
I think we need tests on this before we say SteriPen knows all.
Yes, an interior reflective layer would increase the lifespan of the UV light. Stainless steel bottles would probably increase the effectiveness and drop the required treatment time.
On another note, why do you feel the SteriPen needs to be more effective? I'm fundamentally a skeptic (edit: by nature) myself. I've read over their lab results and, having done similar work in the lab myself, I was convinced right there. Their tests were done properly and could be replicated by anyone who can dilute + plate out bacteria on agar plates and count them. (Harder than it sounds, I don't miss microbiology work at all.) I've read the lab-work of some pretty questionable products and the difference is obvious.
It's also not just their research - there is a very, very large body of research on using UV light and sunlight to disinfect water in general. I'm talking thousands of lab-hours and beyond that in work-hours, not to mention all the people relying on it to get clean water.
If you have more specific questions, the research exists to answer them. How do we know the report isn't falsified? Well, I had written a four-paragraph summary of why scientific research is valid. I removed it in the interests of everyone's eyeballs, and if you really want to know, I'll tell you later <img src="/forums/images/graemlins/grin.gif" alt="" />
(edit) The beauty of science is that if you really doubt the SteriPen's claims, you can test them yourself or pay to test them, then trumpet your results all over the news.