Problem 1: In conventional static or rocking 3D culture systems, nutrients and oxygen reach cells mainly by diffusion, which is too slow to penetrate thick tissues (>200 μm). This leads to necrotic cores and poor viability or maturation. By generating a controlled pressure gradient across the tissue, the invention drives convective perfusion (bulk flow) through the tissue block or hydrogel. This allows continuous exchange of nutrients, gases, and signaling molecules deep inside, extending viable tissue thickness and lifespan. Problem 2: In certain tissues, fluidic cues also shape tissue organization and function. Most organoid or 3D culture systems lack physiologically relevant interstitial flow, an important mechanical cue for morphogenesis, endothelial alignment, and extracellular matrix remodeling. The pressure-driven perfusion creates interstitial shear forces and gradients similar to those in living tissues, improving differentiation and structural organization. Problem 3: Many bioreactors rely on imprecise or uncontrolled flow rates and pressures that do not guarantee a stable or known pressure difference across the tissue. For example, gravity fed microfluidic apparatuses which generate pressure differentials have their pressure gradient constantly changing because the difference in fluidic column height changes as the fluid equilibrates. Rocker based "perfusion" systems have a similar problem because rocking is inherently oscillatory and causes the involved forces to be constantly changing. Problem 4: Capillary to tissue pressure gradients in vivo are on the order of 10-15 mmHg. This is 10 or more times higher than generated by gravity fed or rocker perfusion systems. We anticipate needing a larger pressure gradient for perfusion in thicker tissues as well, since we seek to perfuse tissues much thicker than normal intercapillary distances. In our system, we have successfully generated gradients as high as 200 mmHg (limited by tissue integrity, not by our fluidic actuators.) Problem 5: Surgical specimens or organ slices can’t easily be perfused with microfluidic chips, which are typically designed for engineered scaffolds. By using two fluidic compartments sandwiching any tissue-containing block or hydrogel, the system can adapt to irregular natural tissue samples, not just engineered constructs. Problem 6: Self-contained culture systems with pressure gradient generation within a closed device (such as gravity and rocker devices) often make it difficult to monitor metabolites, oxygen, or pH dynamically. Because fluid continuously circulates through defined compartments, it can integrate inline sensors (e.g., pressure, oxygen, conductivity, FTIR) for real-time monitoring and feedback control.Problem 7: Traditional perfusion systems often require high media volumes or continuous replacement, increasing reagent costs and diluting secreted factors of interest. This design  allows for a closed fluidic loop circulation system minimizes media consumption while maintaining exchange efficiency. The ability to adjust flow and pressure allows optimization for either steady-state homeostasis or accumulation of secreted products.

Expansion Reservoirs in Cell Culture SystemsMost cell culture systems incorporate an expansion reservoir to allow media exchange - the removal and replacement of culture media—without drying out the cells.This function is implemented in various ways, depending on the system design:Conventional culture systems (e.g., wells, flasks, and basic bioreactors) use the culture chamber itself as an expansion reservoir. These chambers hold excess liquid media, which can be gradually removed and replaced. As liquid volume changes, it is balanced by air entering or exiting the chamber.Circulating fluidic systems (e.g., perfusion bioreactors) typically include a dedicated inline expansion reservoir. In these systems, part of the media is actively circulated through the system (“circulation pathway”), while another part remains static in the reservoir. Media is exchanged from the non-circulating volume, with air compensating for the volume change.Flexible bag systems and air-free flexible chamber systems (including recirculating setups) also support media exchange, but instead of displacing air, the flexible container itself changes shape to accommodate volume changes. Despite their differences, all of these systems share key characteristics:- They support variable liquid volumes during media exchange.- They require separate actuators (e.g., pumps or valves) for draining and refilling media. We define all these systems as cell culture systems that rely on an expansion reservoir.Challenges of Expansion Reservoir-Based Systems Mechanical and Control Complexity:Using separate mechanisms for draining and refilling media increases system complexityMultiple actuators must be precisely controlled and synchronized, which introduces more potential points of failure.Media Dilution and Wastage:To avoid drying out the sample, the system must hold both:A minimum media volume to support the biological sampleAdditional dead volume (e.g., in pumps, sensors, and tubing) that must remain wettedIn systems with large dead volumes, this can exceed the minimum required for biological homeostasis, leading to dilution of both:Endogenous substances (e.g., signaling molecules, hormones, biomarkers), which may affect cell behavior or impair data accuracyExogenous additives (e.g., nutrients, growth factors), which are costly and may be wasted.Reduced Sensitivity of Analytical Measurements:Diluted media lowers the concentration of analytes (e.g., metabolic byproducts, gene expression markers), reducing the sensitivity of diagnostic readouts. If some old media remains in the system during exchange, it may delay detection of biological changes.Physical Bulk and System ComplexityExpansion reservoirs add to both the physical size and operational complexity of the apparatus, which can reduce efficiency, increase cost, and complicate system management.Air-Related IssuesIn systems where liquid volume is balanced by air volume, air introduces several risks:Air bubble formation (e.g., from surface exposure or in expansion tanks) can:Disturb gas concentrationsCause local precipitation or concentration of solutesPhysically disrupt cells, sensors, or fluid flow (e.g., by turbulence, blockage, or altered mixing).Evaporation and osmotic imbalance occur when:Air space humidity is insufficient to prevent evaporation or airflow is great enough to cause loss through advectionTemperature or pressure changes affect relative humidity or gas solubility.Gas concentration control is difficult:It either requires active feedback with gas lines and actuators to manage air composition in the dead space, orContinuous air replacement, which increases complexity and promotes further evaporation through water vapor loss due to advection.Other physical parameters that expansion reservoir based systems struggle to control:Fluid Pressure:Having an expansion reservoir, which inherently involves equilibration of the internal pressure of a system with some surrounding environment makes it impossible to maintain the fluid pressure of the entire media compartment of a cell culture system at a pressure other than that of the expansion reservoir.Therefore, to achieve fluidic pressures other than this expansion reservoir pressure, more complicated methods of establishing fluid pressure must be used, such as ones which use active pumping and fluidic resistors or that require repletion of a gravity-pressurized reservoir.In fluid systems, achieving elevated or reduced pressures is crucial for controlling the flow and behavior of fluids within a model, especially when working with fluidic resistors and circulation pumps. Fluidic resistors are components that impede the flow of fluid, and by varying the resistance, they help regulate pressure within a system.When paired with circulation pumps, they provide a dynamic way to maintain or adjust pressure levels. However, using this setup introduces complexity in pressure control. To achieve and maintain the desiredpressure, a pressure feedback control system becomes essential.This system monitors the pressure within the circuit and adjusts the pump's speed or resistance in real time to ensure the pressure stays within the desired range.Without this feedback loop, fluctuations in pressure could lead to inefficiencies or system malfunctions.Pressure feedback control itself adds complexity because it often requires sophisticated sensors, controllers, and algorithms to keep the pressure stable.These systems need to react quickly to changes in fluid dynamics, such as those caused by variations in fluid temperature, viscosity or flow rate.Moreover, the system must be calibrated to handle different conditions, such as varying load demands or system wear over time.Additionally, there is the risk of overpressure, which can occur if the pressure exceeds safe operating limits.In such cases, components like pressure relief valves or bypass lines become critical.Pressure relief valves open when pressure exceeds a certain threshold, allowing excess fluid to be diverted to prevent damage to the system.Bypass lines, on the other hand, allow fluid to flow around the system or around particular components to relieve pressure buildup.Both overpressure relief mechanisms add extra layers of complexity to the design and operation of the system. They must be carefully designed and sized to ensure proper operation under all possible conditions.Without them, there's a significant risk of damaging pumps, resistors, or other sensitive components due to excessive pressure, which could lead to system failure or safety hazards.Elevated or reduced pressures can be achieved in models containing fluidic resistors paired with circulation pumps however these require added complexity in pressure feedback control and may require additional complexity in overpressure relief and/or bypass line components to avoid damaging overpressure events.In a more complex design for expansion reservoirs, elevated or reduced pressures can be achieved in models containing an airliquid interface by simultaneous pressurization/depressurization of the air compartment as well as the liquid compartment, however this alters the relationship between gas partial pressure and gas molar concentration, requiring added complexity in gas provision feedback controlThe difficulty of these approaches is problematic because certain biological processes and tissues require specific pressure conditions that are not at ambient levels, and if these pressure conditions can't be modeled accurately, it is difficult to simulate real-life conditions of certain organ tissues.Some tissues experience pulsatile (regularly changing or "pumping") pressures, such as blood flow through arteries, or even pressure that changes dynamically over time due to body processes.These fluctuating pressures are important for mimicking real physiological conditions. Vascularized tissues (tissues with bloo vessels) rely on pressure gradients (differences in pressure) to function correctly. For example, blood pressure helps circulate nutrients and oxygen throughout tissues.

Live cell microscopes are bulky, limiting costly incubator space. The type and number of light sources is also limited by space constraints inside the incubator. Incubator stage-top microscopes are generally either thermally or gas-inefficient and/or contain limited space for samples, often with constraints on the physical format of samples. Further, placing heat-generating light sources inside an incubator disrupts the temperature and humidity regulation inside the incubator by providing a localized point source of heat not under control of the incubator environmental feedback controller.Additionally, electronics placed inside the warm, humid and acidic environment of a cell culture incubator suffer accelerated wear and corrosion. Either equipment lifecycles are reduced or construction of these devices is more costly.

Cell culture plates are an essential tool for cell biology research. They are used to grow cells in a controlled environment, which allows for study of the effects of different conditions on cell growth and development. The plates are typically made of plastic or glass and may have one or more wells, each of which can hold a small amount of cell culture media. The media provides the cells with the nutrients the cells need to grow and divide. Cell culture plates may be used in incubators to grow cells in a controlled environment. The incubator provides the cells with the necessary conditions for growth, including a constant temperature, humidity, and atmosphere.Conventional cell culture plates are susceptible to evaporation, which causes increased osmolarity of cell culture media. This in turn causes unrealistic growth of cells as well as potential differences between wells due to uneven evaporation. In addition, evaporation causes increased concentration of the salts involved in electrical signaling of electrically active cell types, changing the ionic gradients across the cell membrane, thereby affecting all characteristics of the initiation, transmission (and computation) in electrically active cells such as cardiac or neuronal cells.It is also difficult to maintain desired dissolved gas concentration with standard cell culture plates. This generally requires use of a compressed gas system, which uses gas regulators, sensors that are expensive and have limited lifetimes, and feedback control as well as a glove box for culture and/or handling.An incubator is used to maintain the desired temperature of the cell culture plates, but the incubator impedes access to the cultures for feeding, for microscopy, etc. Furthermore, observation equipment for use inside an incubator needs to be designed to resist incubator conditions (e.g., body temperature heat and humidity). Incubators also take up significant space and packing of incubators in a laboratory is space-inefficient relative to the form factor of the cell culture plates. As the number of cell culture plates in a single incubator increases, the ability of the incubator to perform its function decreases, since there is a minimum number of times an incubator may be accessed per week per cell culture vessel. However, every time the incubator is accessed, it is unable to perform its functions for a prolonged period of time, e.g., over 30 minutes.A further technical problem is that cell culture devices that use an air gap for gas exchange have an increased risk of microbial contamination via that air gap. This makes it difficult to perform manual cell culture experiments over the course of months without contamination. In addition, cross-contamination is more likely if multiple different experiments are being performed in the same laboratory. Thus, there is a need for cell culture vessels and systems that overcome these problems. 

Researchers at the University of California, Davis and Stanford have developed an AI-driven virtual patient platform designed to enhance clinical reasoning skills in emergency medicine learners through dynamic, interactive, and adaptive case simulations.

Cancer inununotherapy heightens the immune system's ability to recognize a cancer and destroy the cancer cells, as opposed to more traditional compounds that directly inhibit the cancer's ability to proliferate. Cancer immunotherapy can provide good responses, even in advanced stages of cancer. Some current immunotherapies include cancer vaccines, antibodies, T cell infusions, and checkpoint blockade therapy. Malignant tumors often co-opt immune suppression and tolerance mechanisms to avoid immune destruction. Immune checkpoint blockade removes inhibitory signals of T-cell activation, which enables tumorreactive T cells to overcome regulatory mechanisms and mount an effective antitumor response. Accordingly, immune checkpoint blockade inhibits T cell-negative costimulation in order to unleash antitumor T-cell responses that recognize tumor antigens.However, only a subset of patients respond to current cancer immunotherapies, and it is difficult to predict which patients will respond. To increase the number of patients who benefit, combination therapies are being used. Cancer vaccine in combination with checkpoint blockade therapy is a promising approach to increasing the antitumor immune response. But, cancers typically have specific mutations (private mutations) in a person or individual tumor and cancer vaccines based on private mutations may be prohibitively expensive and inhibit widespread adoption of this approach. 

A soft, implantable electrical access port enables repeatable, direct connections between implanted bioelectronic devices and external instruments.

A highly selective method for producing P-chiral phosphorus(V) compounds, eliminating complex purification steps while enabling the development of pharmaceuticals, agrochemicals, and other bioactive molecules.