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Sibel Health: designing vital-sign sensors for delicate skin

Close-up of an infant’s foot wearing one of Sibel’s ANNE sensors

Sibel’s monitors don’t require any adhesive tape to stick them to the delicate skin of premature babies.Credit: Northwestern University

Sibel Health is a spin-off from Northwestern University in Evanston, Illinois.

When Shuai Xu, a dermatologist at Northwestern University’s Feinberg School of Medicine in Chicago, Illinois, first placed one of his company’s soft sensors on a premature infant, he felt sure that the research was on the right track. The sensors, which monitor vital signs such as heart rate, blood oxygenation and blood pressure, were small, flexible and light enough to stick to the fragile skin of a baby boy who was so small that he could lie in Xu’s hand. Born at 28 weeks, the child was draped in the wires of conventional monitors. Seeing the electrocardiogram (ECG) reading coming instead from the wireless sensor profoundly affected Xu, he says. “This kind of technology is really going to change the world,” says Xu, now chief executive of Sibel Health in Niles, Illinois. “It’s going to help a lot of these premature infants.”

After his medical degree at Harvard University in Boston, Massachusetts, Xu pivoted to a seemingly unrelated field. He began postdoctoral research in the laboratory of John Rogers, an engineer and materials scientist at the Evanston campus of Northwestern who is responsible for a wide range of developments in flexible electronics. (Sheng Xu, who worked as a postdoc in Rogers’ previous lab, is the co-founder of Softsonics, another finalist in the Nature Research Spin-off Prize.) Xu says that the most important innovation in Sibel’s monitoring device is that it can attach to a premature infant without the adhesive normally used to stick leads to skin. “They’re essentially born without mature skin, so any kind of perturbation of that skin is going to cause injury leading to infection and even death,” he says.

The key to avoiding adhesive lay in making a sensor system that was soft and flexible. The team built its sensors and electronics, such as ECG electrodes and a Bluetooth wireless transmitter, on flexible printed circuit boards, and linked those boards with thin copper wires — 50 to 100 micrometres wide and only 5 micrometres thick, bent in the shape of a serpent. These interconnections made it possible to fold the linked circuit boards over one another so that they took up less area and could fit onto a newborn. Layers of silicone gel above and below the circuit board isolate the electronics. The whole device is enclosed in a form of silicone that bends and stretches easily. Power can be supplied either by a tiny battery, or wirelessly through an attached antenna. A second, similar sensor can wrap around the baby’s ankle and attach to their foot, or be stuck to the bottom of the foot. That sensor contains red light-emitting diodes to measure blood volume and oxygenation.

Because the sensors are very flexible, a baby’s normal movements don’t cause strain between the device and the skin, and there are no wires to pull against. Instead of the adhesive tape normally used for ECG leads, a hydrogel, which is mostly water, provides both electrical conductivity and sufficient adhesion to the skin.

Improving infant care

There were challenges to designing the system that went beyond materials science, Rogers says. The researchers had to tackle computing questions, such as how to synchronize the readings between the chest and foot sensors, and make it simple to use in a clinical setting. “You had to write a graphical user interface that looked exactly the same as the interface the nurses are used to engaging with,” he explains.

Rogers and Xu are optimistic about their progress. For one thing, their system provides information that conventional premature-infant monitors don’t, such as blood pressure. Sibel’s system compares the time difference between pulses recorded by the chest and foot units, and uses that to extrapolate blood pressure. A drop in blood pressure can be the first sign of an infection.

Xu says that the system could also enable the monitoring of innovative biomarkers such as crying patterns, which can be measured by accelerometers in the sensors. Patterns of crying can indicate a baby’s level of pain, or information about their neurological development, he says. All the information the sensors collect is stored, allowing researchers to try to develop predictive algorithms for vital signs.

Prakeshkumar Shah, a neonatologist at Mount Sinai Hospital in Toronto, Canada, who is not involved with the company, says that Sibel’s system could make it easier to include the family in the baby’s care. Freeing the infant of wires “allows the baby not to be stuck in one place”, he says. Studies show that ‘kangaroo’ parenting, in which parents interact with the baby by talking and holding the infant close to their skin, can lead to more rapid weight gain and reduce the length of stay in the intensive-care unit, as well as reducing re-admission rates and parental anxiety, he explains.

Shah says he would be willing to introduce the sensor at his hospital, if the cost were reasonable and if the medical team were comfortable with it. He’d also like to see the researchers expand the range of babies on whom they validate their system. A report1 this year looked at using the sensors on premature infants with vital signs in a normal range, which Shah says covers about 85% of patients. But it will be important, he says, to show how well the technology works with babies whose blood pressure or oxygen levels drop well below the normal range.

Sibel hopes to receive approval to use the system in both the United States and Europe by September, although this could be delayed as a result of the coronavirus pandemic. The company is already selling sensors for research purposes in 17 countries worldwide. The sensors could be particularly popular in low- and middle-income countries that cannot afford a lot of expensive monitoring equipment, Rogers says, because they can be used with smartphones. That can reduce the cost of monitoring from US$60 to less than $0.10 per day, he says.

Sibel, which was founded in 2018, has 20 employees and has filed international applications for 5 patents. The company does not disclose exact funding figures, but Rogers estimates that it has probably received “more than $10 million”.

Shah hopes the company will be successful because its technology has the potential to allow families to have invaluable interaction with premature infants in a way that the most sophisticated current medical equipment does not. “It will not only allow us to be wireless,” he says. “It will also allow us to be human.”


This article is part of Nature Outlook: The Spinoff Prize 2020, an editorially independent supplement produced with the financial support of third parties. About this content.

Updates & Corrections

  • Correction 09 July 2020: An earlier version of this profile erroneously referred to Xu as the chief operating officer.

  • Update 21 July 2020: This article has been updated to reflect the fact that Sibel Health won The Spinoff Prize.


  1. 1.

    Chung, H. U. et al. Nature Med. 26, 418–429 (2020).

    PubMed  Article  Google Scholar 

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