Q: What is wrong with the "abstract" field? http://www.jeos.org/index.php/jeos_rp/article/view/12033
I just use the bibtex, that you get when you click "cite this article" and changed the bibtex-Key to "Lipka2012".
\documentclass{article}
\usepackage[backend=biber]{biblatex}
\addbibresource{Test.bib}
\begin{document}
\cite{Lipka2012}
\end{document}

As long as the Abstract is in the Test.bib, Biber fails and gives me the following message:
(CiteTest.aux) (CiteTest.bbl)
Runaway argument?
{This paper reports about hydrogenated amorphous silicon which can be\ETC.
! File ended while scanning use of \field.
<inserted text> 
                \par 
l.6 \begin{document}

? 

So what's the matter and how can I resolve this? Deleting the abstract field would be unfortunate.
The bib entry from the site with the changed bibtex-Key: 
   @Article{Lipka2012,
  author   = {T. Lipka and O. Horn and J. Amthor and J. Müller},
  title    = {Low-loss multilayer compatible a-Si:H optical thin films for photonic applications},
  journal  = {Journal of the European Optical Society - Rapid publications},
  year     = {2012},
  volume   = {7},
  number   = {0},
  issn     = {1990-2573},
  abstract = {This paper reports about hydrogenated amorphous silicon which can be employed as low-loss optical material for small footprint and cost-effective photonic integrated circuits. Basic waveguides, photonic wire based couplers, Mach-Zehnder interferometers, ring resonators and Mach-Zehnder assisted ring resonators were designed, fabricated, and optically characterised. The propagation loss of rib and photonic wire waveguides were determined to be 2 dB/cm and 5.3 dB/cm, respectively. The 90° bending losses of 5 µm curved photonic wires were determined to be 0.025 dB/90°. Three-dimensional tapers, which were fabricated without additional etching steps and were deposited on top of the fabricated photonic wires showed a net coupling loss of 4 dB/port. Multimode 3 dB-splitters were systematically investigated resulting in 49-51% splitting ratios. Mach-Zehnder interferometers that were realised with these splitters showed interference fringe depths of up to 25 dB for both polarisations. Compact ring resonators with 10 µm radius implemented as notch filters and in Mach-Zehnder coupled configurations provided extinction ratios of ≥20 dB and Q-factors up to 7500.},
  keywords = {dielectric thin films; amorphous silicon; integrated optics; photonics; resonators},
  url      = {http://www.jeos.org/index.php/jeos_rp/article/view/12033},
}


A: If all you need to get accomplished is to prevent bibtex (or biblatex) from crashing, simply replace the instance of % in the abstract field with \%. Recall that % is the comment character in TeX/LaTeX. 
If there's a chance that you may need to produce an extended bibliography, in which the abstracts of various publications are shown, it would be a good idea to replace edit the abstract field more thoroughly. E., replace several special characters -- °, µ, and ≥, and probably a few others more -- with terms that LaTeX can process correctly. Also, consider making use of the \SI macro (provided by the siunitx package) to typeset physical quantities and units correctly and consistently.
The following MWE uses BibTeX and the abstract bibliography style, since that's the only bib style I'm aware of that typesets the contents of any abstract fields.

\RequirePackage{filecontents}
\begin{filecontents}{mybib.bib}
@Article{Lipka2012,
  author   = {T. Lipka and O. Horn and J. Amthor and J. Müller},
  title    = {Low-loss multilayer compatible {a-Si:H} optical 
              thin films for photonic applications},
  journal  = {Journal of the European Optical Society---Rapid publications},
  year     = {2012},
  volume   = {7},
  number   = {0},
  issn     = {1990-2573},
  abstract = {This paper reports about hydrogenated amorphous silicon which 
      can be employed as low-loss optical material for small footprint and 
      cost-effective photonic integrated circuits. Basic waveguides, photonic wire 
      based couplers, Mach-Zehnder interferometers, ring resonators and Mach-Zehnder 
      assisted ring resonators were designed, fabricated, and optically characterised. 
      The propagation loss of rib and photonic wire waveguides were determined to be 
      \SI{2}{\deci\bel\per\centi\meter} and \SI{5.3}{\deci\bel\per\centi\meter}, 
      respectively. The \SI{90}{\degree} bending losses of \SI{5}{\micro\meter} curved 
      photonic wires were determined to be \SI{0.025}{\deci\bel}/\SI{90}{\degree}. 
      Three-dimensional tapers, which were fabricated without additional etching steps 
      and were deposited on top of the fabricated photonic wires showed a net coupling 
      loss of \SI{4}{\deci\bel}/port. Multimode \SI{3}{\deci\bel}-splitters were 
      systematically investigated resulting in 49--51\% splitting ratios. Mach-Zehnder 
      interferometers that were realised with these splitters showed interference 
      fringe depths of up to \SI{25}{\deci\bel} for both polarisations. Compact ring 
      resonators with \SI{10}{\micro\meter} radius implemented as notch filters and in 
      Mach-Zehnder coupled configurations provided extinction ratios of $\ge\SI{20}
      {\deci\bel}$ and Q-factors up to~7500.},
  keywords = {dielectric thin films; amorphous silicon; integrated optics; photonics; resonators},
  url      = {http://www.jeos.org/index.php/jeos_rp/article/view/12033},
}
\end{filecontents}
\documentclass{article}
\usepackage{url,siunitx}
\sisetup{per-mode=symbol}
\usepackage[numbers]{natbib}
\bibliographystyle{abstract}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\begin{document}
\cite{Lipka2012}
\bibliography{mybib}
\end{document}

