Researchers at the University of Twente’s TechMed Centre have developed a soft robotic mini-tablet that can measure acidity in the stomach in real time and, on command, collect gastric fluid for laboratory analysis. The technology, called SeroTab, is intended as a less invasive alternative to existing diagnostics for gastrointestinal complaints. In future, the tablet could therefore contribute to faster triage, earlier detection and more targeted treatment of gastrointestinal disorders.
Gastrointestinal diseases represent a major burden of care worldwide. At the same time, diagnosis is often complex. GPs and primary care providers usually have limited resources, whilst advanced diagnostic methods such as endoscopy, CT or X-ray examinations are costly, invasive and not always immediately available. It is precisely here that a compact, swallowable diagnostic technology can offer added value.
Smart materials
The SeroTab stands out because the tablet contains no built-in electronics. This is important because traditional capsule technology often faces limitations regarding miniaturisation, battery power, biocompatibility and passive movement through the gastrointestinal tract.
Instead, SeroTab combines soft robotics, magnetic control, responsive materials and ultrasound. The tablet has a soft, biocompatible casing and can be guided through the stomach using an external magnet. Its movement is inspired by the gliding motion of penguins through viscous environments. Magnetic forces cause the tablet to bend slightly with the anatomy, enabling it to pass through obstacles and mucosal folds more easily.
This active positioning is a key difference from existing capsule endoscopy, where capsules mainly move passively with peristalsis. SeroTab can be directed to a specific area in the stomach and anchored there for local measurement and sampling.
Combining functions
The core of the technology lies in the combination of two functions: rapid on-site pH measurement and sampling of gastric fluid for subsequent molecular analysis. Gastric pH is clinically relevant, as changes are associated with conditions including reflux disease, gastric ulcers, gastritis, infections and potentially gastric cancer.
The tablet contains a pH-sensitive hydrogel. As soon as gastric fluid reaches the internal chamber, this hydrogel swells depending on the acidity. Small biocompatible metal markers in the gel make it possible to track the volume change using ultrasound. This allows the pH to be read without electronics within a physiologically relevant range of pH 2 to 7.
In addition, the tablet can absorb gastric fluid into an internal reservoir of up to approximately 35 microlitres. This is achieved via an actuator made of shape-memory polymer, a material that returns to its original shape after external activation. Activation takes place wirelessly via radio-frequency heating. The change in volume creates negative pressure, causing gastric fluid to be drawn into the chamber via a microchannel. A Tesla valve helps prevent backflow and leakage.
Results in animal models
The researchers tested SeroTab in laboratory setups, ex vivo pig organs and live animal models. In rabbits, it was demonstrated that the tablet can be swallowed, magnetically positioned, remotely activated and tracked using ultrasound.
A key part of the study was measuring pH changes following the administration of omeprazole, a proton pump inhibitor that inhibits gastric acid secretion. The SeroTab was able to detect the medication-induced rise in pH, from approximately pH 2 to pH 6. According to the researchers, clear changes in the hydrogel’s volume were visible within ten minutes, which were sufficient for pH determination, although the full experimental procedure in the animal model took approximately seventy minutes.
After removal of the tablet, the hydrogel was used for mass spectrometry. This detected the omeprazole component and 42 related metabolites, including amino acids and bile acid-related compounds. The analysis revealed changes in, among other things, bile acid and tryptophan metabolism, pathways associated with gastric acid regulation and interactions with the microbiome.
Potential for precision diagnostics
The potential added value of SeroTab lies not only in pH measurement, but primarily in the diagnostic workflow model that the technology enables. A rapid local pH measurement can serve as an initial indicator. If this is abnormal, the collected sample can then be analysed in depth for metabolites, biomarkers or other molecular signals.
This could be relevant for early screening, monitoring of treatment and personalised care. In patients taking proton pump inhibitors, for example, the technology could help to better monitor the effect of medication and potential metabolic side effects. In other gastrointestinal diseases, local molecular sampling may contribute to earlier detection of pathological processes.
For healthcare, the promise of a less invasive, outpatient diagnostic approach is particularly interesting. Instead of immediately referring patients to burdensome or costly procedures, a swallowable robotic tablet could potentially assist with triage and decision-making in primary or secondary care in the future.
No clinical application yet
At the same time, SeroTab is still in the early stages of translation to the clinic. The current results are based on animal models and experimental setups. Further miniaturisation, safety studies and research into natural passage through the gastrointestinal tract are required before application in humans is conceivable.
The clinical workflow also needs to be simplified. The current prototype approach still requires the coordinated use of magnetic control, radiofrequency heating and ultrasound. The researchers therefore see potential in integration with robotic positioning, AI-supported image recognition and possibly wearable ultrasound technology.
If these steps are successful, SeroTab could develop into a new type of diagnostic platform: a soft, electronics-free robot that measures locally, takes targeted samples and makes molecular information available without traditional invasive procedures. The technology thus fits into a broader movement towards earlier, more precise and patient-friendly diagnostics in gastrointestinal care.
