A neural colloid, commonly referred to as simply a colloid and sometimes with the portmanteau neuroid, is a class of human-implantable multielectrode arrays (MEAs) primarily designed to wirelessly read and stimulate neural activity in the brain. The name stems from the method used to administer the electrodes, which involves suspending them in a colloid and injecting them into the body, after which they migrate to different parts of the brain.
First designed in 2015 as an implantable polymer mesh studded with electrodes to sample individual neurons and treat neurological disorders, colloids in their current form were developed by Endoptic and entered widespread use with the international adoption of G6 in 2041. While many medical, commercial, and military applications exist, the most common colloid is the line of G6-BASIC colloids in use by G6, representing over 65% of all implanted colloids.
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The development of neural colloid technology was enabled by several key advances in brain-computer interfaces (BCIs) and implantable medical devices (IMDs). Its first iteration was devised in 2015 by a team of physicists, neuroscientists, and chemists at Harvard University working on brain-injectable electronics. Using a syringe-implanted macroporous mesh of conductive polymer threads with electrodes at their intersections, the team was able to both monitor and stimulate activity from a large number of individual neurons in the brains of mice. 
In the early 2020s, a research group at UC Berkeley led by Yang Peidong further refined the implant design by introducing the use of short-range visible light to network the electrodes together in the brain, as well as a wireless method of data transmission using high-frequency radio telemetry. These advances eliminated the need for a conductive mesh or a physical BCI connection that leads outside of the cranium, resulting in a more flexible multielectrode array (MEA) configuration with increased spatiotemporal resolution and a higher signal-to-noise ratio.
Colloids in their modern form were developed by Endoptic, which was founded in 2027 by Spencer Hagen, previously a member of the UC Berkeley research group. In 2030, a breakthrough in AlphaFold-enabled protein targeting led Endoptic to devise an electrode implanting method that did not involve a needle injected into the target region of the brain. By coating the electrodes in synthesised proteins so they bind to relevant tissue and suspending them in a colloid, they would migrate to specified parts of the brain via the circulatory system after intramuscular injection. 
Additionally, the protein coatings allowed for the electrodes to persist within the body for an entire lifetime without the need for bulk enclosures, which also reduced the electrodes in size. Subsequent trials in animal models relevant for human translation indicated that Endoptic’s implantable MEAs revealed rich neural data hidden by traditional approaches such as extracranial electroencephalography (EEG) and conventional electrocorticography (ECoG).
In 2031, long-term biocompatibility trials of the MEAs in animals resulted in cases of cerebral small vessel disease (CSVD), which were attributed to the blockage of capillaries in the brain by the electrodes. As a result, Endoptic reached out to Parisa Mirkarimi, whose research at Stanford University had resulted in the development of flexible artificial pseudoplastic (FLAPP), a polypyrrole-based nanomaterial that can mimic the folding properties of red blood cells (RBCs). Mirkarimi joined Endoptic in July 2031 and worked with Hagen’s research and technological development (RTD) team to produce FLAPP nanomaterials for the company’s MEAs.
In 2032, Endoptic joined Zhupao Campus and began human trials for its neural colloid MEAs, so named for the implant’s administration method. The trials drew widespread media attention due to the involvement of Efrim Waite, who had volunteered to be the first human subject of a colloid implant and livestreamed the process on August 1st 2032, with Hagen personally administering the colloid. This led to an influx of requests from Waite’s fans to sign up to Endoptic’s human trials, which drew ire from the medical community, as colloids were still the subject of biocompatibility tests in animals at the time. In several interviews, Waite has expressed the belief that colloids are a highly beneficial technological development, stating that “colloids, rather than interstellar travel, are mankind’s only chance to see what lies beyond the primeval muck.” 
In 2034, Zhupao was faced with calls to pull its support of Endoptic after it was reported that the Chinese Communist Party (CCP) and Huawei had been testing early designs of implantable MEAs on detainees in the Xinjiang concentration camps. This had resulted in numerous cases of CSVD in the camps, which initially went unnoticed due to similar medical and psychiatric issues arising from the mistreatment of detainees. In a joint statement with Hagen, Xu Shaoyong claimed that Endoptic had no involvement with the CCP’s activities in the camps, stating that Endoptic only worked with consenting volunteers for their trials with colloids.
In 2036, Endoptic was incorporated as a subsidiary of Zhupao, which officially unveiled colloids as a new class of implantable MEAs and “the biggest paradigm shift in consumer technology since smartphones.”  On October 25th 2036, Xu personally injected a colloid while on stage and pinged a live connection to his cerebral cortex, claiming that the audience was “witnessing [his] consciousness down to the level of individual neurons.” Xu also praised the advancements in neurotechnology and “the fundamental understanding of the human mind” that colloids had enabled, and congratulated Hagen for “the democratising of brain augmentation.”
In 2038, colloid technology was approved by the Therapeutic Products Directorate (TPD) as a Class II “intermediate-risk” IMD, allowing Zhupao to partner with select physicians and hospitals across Canada to apply colloids to the neurostimulative diagnosis and treatment of various neurological disorders. Following the shutdown of Neuralink after it was linked to the spread of Cariappa-Muren disease (CMD) in the United States (US), the Food and Drug Administration (FDA) expedited its approval process for colloids in November 2039.
On December 8th 2039, Xu announced an agreement between Zhupao and the World Health Organisation (WHO) to manufacture and supply diagnostic colloids for the WHO’s contact tracing efforts to contain the CMD pandemic.  In the press briefing, Xu credited Hagen with spearheading the development of the diagnostic colloids, which were equipped with chemical nanosensors to detect CMD-related breakdown products in brain tissue.  In September 2040, Zhupao revealed a new line of colloids that were being administered in China as part of a series of GPHIN 2.0 pilot programmes. On September 23rd 2040, Xu injected one of the colloids himself and explained that their individual electrodes contained the necessary hardware to support both CMD-specific diagnostic sensors and a means of neurometric identification based on the CEREBRE protocol. 
In March and April 2041, the WHO organised several working groups with Zhupao and the International Telecommunication Union (ITU) to outline the terms of a WHO charter for the international use of G6, including the parameters of the network’s deployment of colloids. In April 2041, Zhupao presented G6-BASIC as a “baseline, opt-in” licensing tier for the implementation of G6, with the stipulation that the network’s colloids may not be exploited for any purpose other than health informatics and biosecurity.
Zhupao’s rollout of colloids was delayed in June 2041 due to the impact of Typhoon 4109, which destroyed Endoptic’s main production facility in Borneo and severely limited the company’s manufacturing capacity until the fall of 2041, when construction on eight new facilities outside Colombo, Sri Lanka was completed. 
In 2045, the Russian government launched a criminal investigation into Pokrov, accusing the company of illegally reverse engineering colloid technology. This was followed by additional civil suits filed by Zhupao, alleging that Pokrov had been developing and selling collocidals since 2042. In a public statement, Yuri Golitsyn denied any wrongdoing and condemned Zhupao for “deliberately misrepresenting the long-term risks of colloid implants.”
In 2047, a rise in cases of CSVD in countries subscribed to G6 was linked to colloids, with every recorded patient having at least one colloid implant. In November 2047, Hagen attributed the surge in CSVD to third-party colloid manufacturers without a license to Endoptic’s FLAPP nanomaterials. As of 2049, approximately 72% of the world population is implanted with at least one colloid, with the G6-BASIC colloid representing over 65% of all implanted colloids.
A neural colloid consists of a network of nanoscale electrodes dispersed through a saline solution, which is typically injected into the deltoid muscle in the upper arm. The electrodes themselves are partially modelled on artificial cells to ensure their biocompatibility, which includes a lipid bilayer coating that acts like a cell membrane. This membrane can be tailored to the recipient’s immune system via a blood sample, allowing it to synthesise and express the cell surface proteins appropriate for the desired implant sites in the brain, such as L1, CD31, the interleukin-1 receptor antagonist (IL-1RA), and the glial fibrillary acidic protein (GFAP).  After injection, the electrodes pass through the circulatory system until they nestle in the vasculature of the brain as directed by the protein coating, which integrates the electrodes into the tissue, suppresses any immune response against them, and allows them to contribute to normal brain function.
The electrodes are shaped like biconcave discoids and measure 8 µm (0.008 mm) in diameter, which allows them to pass through the blood-brain barrier (BBB). They are nanosculpted from FLAPP nanomaterials composed of a light-sensitive elastic polymer, which aids in the actuation of polylobed interlocking shapes so the electrodes can reduce their surface area by folding into each other, matching the stacking configurations of RBCs suspended in blood plasma.  This stacking process, which mimics shear thinning in blood flow dynamics, decreases viscosity and prevents the electrodes from blocking capillaries in the brain, a controversial issue that plagued early colloid designs.
To coordinate the stacking behaviour and synchronise spatial orientation, the electrodes communicate with each other using high-bandwidth light over distances up to 3 cm, the maximum tolerable distance visible light can pass through brain tissue. Their biobatteries are powered by a wraparound chemical film that enables them to oxidise glucose. G6-BASIC colloids are made up of electrodes that have an additional onboard chemical sensor for the detection of CMD-related breakdown products in the brain, even when initially present at only one part in a hundred billion (10−11). 
The wide range of military and civilian applications of colloids are dependent on the external firmware and corresponding privileges that interact with them, as they generally have static hardware following the implant procedure. The firmware and signal processing tools for colloid technology are based on OpenBCI, with colloid-specific modifications made by a collaborative project between Endoptic and an artificial intelligence (AI) research team led by Efua Amankwah-Crouse, who implemented the Pacotti architecture for pattern recognition approaches to localising neural targets and identifying event-related potentials (ERPs). In 2036, Xu credited Amankwah-Crouse with “having provided the leaps forward in AI and software design needed to make colloids work.”
Colloids serve as a key part of treatments for loss of organ and limb function, paralysis, chronic pain, sensory loss, and motor disorders such as essential tremor, Parkinson’s disease (PD), epilepsy, and dystonia. They generally operate by normalising or modulating nervous tissue function and substituting a motor, sensory, or cognitive modality that was damaged as a result of injury or disease.
Neurostimulation had proven its effectiveness as a therapeutic tool for mental disorders before the introduction of colloids, but their use has significantly reduced the medical expenses involved and largely eliminated the trial-and-error process of prescription medications. Colloids are now extensively applied in treatments for, among others, anxiety, depression, loneliness, stress, obsessive-compulsive disorder (OCD), and posttraumatic stress disorder (PTSD).
When pinged by an external reader, a neurometric colloid produces a montage, which can be analysed for individually unique patterns and verified against a stored montage that was recorded during the colloid’s calibration.  Endoptic describes this as a “multifactor authentication process, where a biometric or other initial factor serves as a user name, and the neurometric ping represents the password.” A montage is impossible to fake due to the inherent rhythmic variances in EEG readouts between pings, rendering a replay attack with a static montage useless because it is easily detected as too perfect a match.
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