Craniobot & See-Shells

Type: Other Hardware Development,

Keywords: Robotic Surgery, Polymer Skull, Cranial Procedure

Robotic platforms for automated cranial microsurgery and transparent polymer skulls for neural interfacing

We have developed (1) robotic platforms for automated cranial microsurgeries. (2) transparent polymer skulls for cortex-wide neural interfacing. (1) is currently being setup at multiple groups and we are helping these groups beta test. (2) is being shared via material transfer agreement to several groups at the NIH, Stanford, MIT, Johns Hopkins, UC Boulder and Princeton. We provide starter kits – with fully assembled implants, and raw materials for making dozens more. We hope to use STTR funds soon to be provided by the BRAIN Initiative to develop commercial versions of both.

* Craniobot – a robotic surgery platform that utilizes principles of computer numerical control (CNC) machining to perform a wide variety of automated cranial procedures
* Utilizes a low force contact sensor to profile the skull surface and uses this information to perform micrometer-scale precise milling operations within minutes
* Soft robotic grippers along with motorized scalpels could automate the excision of scalp, vacuum graspers could automate the bone excision process, implant holders could be programmed for automatically positioning the implant, and integrated fluidic circuits could be utilized for application of fast-curing cement during implantation
* Engineering a suite of tools that enable access and interface with large parts of the cortex at high spatial and temporal resolution
* Automated surgical tools will empower the neuroscience community to deploy new neurotechnology in ever increasingly complex procedures
* See-Shells – transparent polymer skulls that allow long-term optical access to 45 mm2 of the dorsal cerebral cortex in the mouse
* Digitally designed, morphologically realistic
* Demonstrate the ability to perform mesoscopic imaging, as well as cellular and subcellular resolution two-photon imaging of neural structures up to 600 µm deep
* Allow calcium imaging from multiple, non-contiguous regions across the cortex
* Perforated See-Shells enable introducing penetrating neural probes to perturb or record neural activity simultaneously with whole cortex imaging
* Can be inexpensively fabricated using desktop prototyping tools, providing a powerful tool for investigating brain structure and function
* Can be implanted using methodologies adapted from standard cranial window implantation procedures
* Can be chronically implanted for long durations (>300 days)
* Ca2+ imaging can be performed at both mesoscale and cellular resolution from populations of neurons spread across millimeters of the cortex during awake, head-fixed behavior
* Allow optical access to a large part of the dorsal cerebral cortex for high-resolution structural and functional imaging
* Provide optical access to ~1 million neurons from the cortical surface
* Chronic imaging over 48 weeks provides the opportunity for very long-term studies of brain development, plasticity and learning, disease processes, and evaluation of new therapies
* The See-Shells methodology can be adapted to build customized implants derived from computed-tomographic (CT) scans of the skull, enabling imaging of neural activities across centimeters of the non-human primate (NHP) cortex
* Several aspects of the design and fabrication of the See-Shells are widely adoptable and highly flexible
* All extracellular recording data were post-processed using custom MATLAB scripts

* Automatically performing four types of cranial procedures: circular craniotomies of a desired diameter and location, craniotomies of arbitrary shapes as specified by the user, surface milling for skull thinning and drilling pilot holes for bone anchor screw implantation
* Performing circular craniotomies for coverslip implantation, large craniotomies for implanting transparent polymer skulls for cortex-wide imaging access and skull thinning for intact skull imaging
* Demonstrated wide-field Ca2+ imaging with simultaneous intracortical microstimulation and electrophysiological recordings
* Using See-Shells to combine wide-field Ca2+ imaging with in vivo patch clamping methodologies to record from single and multiple neurons will help us to better understand how mesoscale network activity influences sub-threshold membrane potential dynamics in individual neurons
* Used perforated See-Shells to perform intracortical microstimulation

* Mice

* Used for surgeries on adult mice of ages 8–16 weeks
* High-quality mesoscopic Ca2+ imaging in the awake animal has been performed in mice implanted with See-Shells for 48 weeks, the longest period tested to date
* See-Shells could also be engineered for optical interfacing with complex and mobile anatomical structures such as the spine
* Engineering See-Shells embedded with these miniaturized lens-less imaging systems offers the possibility of monitoring the activity of the whole cortex during freely moving behaviors

* Can be set up in <2 weeks using parts that cost <$1,500
* Easily adapted for use in other small animals
* Can be performed on mice of other ages as well as on other small animals such as rats
* Craniobot is useful when performing large craniotomies, particularly in regions of the skull where there may be vasculature and also for skull-thinning operations
* Open source
* G-code programming language used by the Craniobot can be harnessed to incorporate additional capabilities and perhaps automate the entire surgical procedure
* MATLAB environment
* Custom Graphical User’s Interface
* Customized to fit a variety of skull morphologies and allow for sub-cellular resolution structural imaging
* Easily adapted to include perforations for penetrating stimulation or recording probes
* Optical imaging with See-Shells can be combined with other modalities

* May not significantly enhance the speed of the procedure overall in comparison to manual procedures due to surface-profiling step
* Stereotax: fine adjustments to the relative heights and position of the bite bar and nose cone with respect to ear bars is tedious, as there is no adjustment screw mechanism
* Primary limitation will be skull growth in the postnatal period
* Imaging across the whole field of view (FOV) simultaneously at high resolution is currently not possible

* Rynes et al. 2020, Assembly and operation of an open-source, computer numerical controlled (CNC) robot for performing cranial microsurgical procedures, Nature Protocols 15:1992–2023

* Ghanbari et al. 2019, Cortex-wide neural interfacing via transparent polymer skulls, Nature Communications 10: 1500


Suhasa Kodandaramaiah, Assistant Professor


University of Minnesota Twin Cities



Mark Thomas (UMN)
Mar Harnett (MIT)
Timothy Ebner (UMN)
Sarah Swisher (UMN)
Lyudmila Vulchanova (UMN)
Daryl Gohl (UMN)
Roarke Hortsmeyer (Duke)
Weiland Huttner (Max Planck, Dresden)