MIT researchers discovered that laser light in a multimode optical fiber can spontaneously self-organize into a highly focused 'pencil beam' under two precise conditions: zero-degree entry angle and near-maximum power. This counterintuitive phenomenon — where increased power reduces chaos rather than amplifying it — enables 3D biomedical imaging of the human blood-brain barrier 25 times faster than current gold-standard methods. The technique requires no fluorescent cell tags and can track drug absorption at the cellular level in real-time, potentially accelerating development of therapies for Alzheimer's, ALS, and other neurodegenerative diseases. The work is published in Nature Methods.
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