Abstract
A transparent and penetrable cranial window is essential for neuroimaging, transcranial injection and comprehensive understanding of cortical functions. For these applications, cranial windows made from glass coverslip, polydimethylsiloxane (PDMS), polymethylmethacrylate, crystal and silicone hydrogel have offered remarkable convenience. However, there is a lack of high-strength, high-transparency, penetrable cranial window with clinical application potential. We engineer high-strength hybrid Titanium-PDMS (Ti-PDMS) cranial windows, which allow large transparent area for in vivo two-photon imaging, and provide a soft window for transcranial injection. Laser scanning and 3D printing techniques are used to match the hybrid cranial window to different skull morphology. A multi-cycle degassing pouring process ensures a good combination of PDMS and Ti frame. Ti-PDMS cranial windows have a high fracture strength matching human skull bone, excellent light transmittance up to 94.4%, and refractive index close to biological tissue. Ti-PDMS cranial windows show excellent bio-compatibility during 21-week implantation in mice. Dye injection shows that the PDMS window has a “self-sealing” to keep liquid from leaking out. Two-photon imaging for brain tissues could be achieved up to 450 µm in z-depth. As a novel brain-computer-interface, this Ti-PDMS device offers an alternative choice for in vivo drug delivery, optical experiments, ultrasonic treatment and electrophysiology recording.
Highlights
Studies on brain functions face a natural barrier that the brain is tightly protected underneath the skull
The locking parts were inserted into the gap between skull bone and brain tissue, and firmly fixed a Ti-PDMS cranial window to cranium without screws
No bubbles were observed in the window region. These results prove that our fabricating processes for the Ti-PDMS windows are highly effective
Summary
Studies on brain functions face a natural barrier that the brain is tightly protected underneath the skull. FMRI provides an excellent aid for the study of psychiatric disorders [3,4]. For two-photon experiments and fluorescence measurements, cranial surgery is performed in installation of many novel brain-computer-interfaces (BCIs) [27,28,29,30,31,32,33]. For these applications, a transparent artificial cranial window with good mechanical strength may play an important role
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