You will be shown an abstract from a biomedical research paper. Given this abstract, your task is to extract all unique entities of the following types: ["Chemical"].

Please return the output as a JSON object of the format: {"Chemical": ["Arsenic", ...]}. The keys should be entity types and values should be lists of extracted entities belonging to the corresponding type. If you cannot find entities belonging to a specific type, the value should be [].

Only output the JSON object and do not include any additional text.

Abstract:

A new perfluoropolyether-based hydrophobic and chemically resistant photoresist structured by two-photon polymerization. Two-photon polymerization technology has been used to fabricate submicrometer three-dimensional (3D) structures using a new polyfunctional perfluoropolyether-based resist, which is a polymer intrinsically hydrophobic and chemically resistant. The fluorinated resist was designed and synthesized in this work and successfully employed to fabricate woodpile structures in various experimental conditions. This is the first demonstration of the capability to fabricate hydrophobic and chemically resistant 3D structures with submicrometer resolution and arbitrary geometry.
{"Chemical": ["perfluoropolyether"]}