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:

Probing circulating tumor cells in microfluidics. Circulating tumor cells (CTCs) are important targets for study as we strive to better understand, diagnose, and treat cancers. However, CTCs are found in blood at extremely low concentrations; this makes isolation, enrichment, and characterization of CTCs technically challenging. Recently, the development of CTC separation devices has grown rapidly in both academia and industry. Part of this development effort centered on microfluidic platforms, exploiting the advantages of microfluidics to improve CTC separation performance and device integration. In this Focus article, we highlight some of the recent work in microfluidic CTC separation and detection systems and discuss our appraisal of what the field should do next.
{"Chemical": []}