This smart pacifier can also provide more continuous monitoring of sodium and potassium ion levels.
These electrolytes help alert caregivers if babies are dehydrated, a danger for infants, especially those born prematurely or with other health issues.
Researchers tested the smart pacifier on a selection of infants in a hospital, and the results were comparable to data gained from their normal blood draws. They detailed their findings in a proof-of-concept study published in the journal Biosensors and Bioelectronics.
“We know that premature babies have a better chance of survival if they get a high quality of care in the first month of birth,” said Jong-Hoon Kim, associate professor at the Washington State University School of Engineering and Computer Science and a co-corresponding author on the study.
“Normally, in a hospital environment, they draw blood from the baby twice a day, so they just get two data points. This device is a non-invasive way to provide real-time monitoring of the electrolyte concentration of babies.”
Other methods have been developed to test an infants’ saliva for these electrolytes, but they involve bulky, rigid devices that require a separate sample collection.
Using a common, commercially available pacifier, the researchers created a system that samples a baby’s saliva through microfluidic channels. Whenever the baby has the pacifier in their mouth, saliva is naturally attracted to these channels, so the device doesn’t require any kind of pumping system.
The channels have small sensors inside that measure the sodium and potassium ion concentrations in the saliva. Then this data is relayed wirelessly using Bluetooth to the caregiver.
For the next step of development, the research team plans to make the components more affordable and recyclable. Then, they will work to set up a larger test of the smart pacifier to establish its efficacy.
Kim said development of this device is part of a broader effort to help make NICU treatment less disruptive for their tiny patients.
“You often see NICU pictures where babies are hooked up to a bunch of wires to check their health conditions such as their heart rate, the respiratory rate, body temperature, and blood pressure,” said Kim. “We want to get rid of those wires.”
Along with Kim, co-authors on this study include researchers from Georgia Institute of Technology, Pukyong National University and Yonsei University College of Medicine in South Korea as well as WSU.
Pacifier Design: The pendant Drop The pacifier device aims to provide continuous, real-time measurement of glucose in the infant’s saliva. To achieve real-time monitoring, it is necessary a continuous and unidirectional flow of saliva on the sensor’s surface. Therefore, a commercial pacifier was needs to be modified to transport saliva from the infant’s mouth to the sensor, located on the back of the pacifier, without any backflow.
The design was constrained by the pacifier geometry, the human saliva production rate and the use of safe materials. The saliva transport was made by a small Polyvinyl chloride (PVC) tube placed inside the pacifier nipple connecting the pacifier tip (in contact to the mouth) to the back of the pacifier (where the sensor is located).
Therefore, the pacifier geometry defined the tube length, which was set to 3.6 cm, the distance from the pacifier tip to the sensor location. Once the tube length was defined, its diameter was selected to provide an adequate flow rate. The flow rate is determined by the saliva production rate which for a human is on average 0.3 mL/min if unstimulated and a maximum of 7 mL/min if stimulated1.
Since the expected flow rate is very low, the tube diameter is also expected to be small, therefore viscous effects and capillarity are expected to be dominant on this scale. To meet the unidirectional constant flow to the sensor, we need to provide a mechanism to drive the saliva flow to the sensor while avoiding backflow to the infant’s mouth.
Given the low flow rate dominated by capillarity and viscous effects, and the geometric limitations, a suitable design was inspired by the Pasteur pipette and by the pendant drop tensiometry method (Figure S4). The Pasteur pipette can generate a unidirectional flow, provided that the fluid displacement is larger than the critical droplet size, by means of the compression and release of its bulb.
An important distinction between the proposed design and the Pasteur pipette is the fact that while for the pipette, the fluid enters and leaves the pipette interior by the same orifice, the pacifier device requires the flow to enter by one side and leaves the device on the other end (See the conceptual design in Figure S4,b).
Once the pacifier is inserted in the infant’s mouth it is the bulb. The parcel of fluid displaced to the sensor must not return to the infant’s mouth. Thus, the presented shape is necessary to prevent backflow from the sensor end. From the pendant drop tensiometry we know that droplet size can be controlled by a needle outlet geometry, material and fluid properties.
A maximum droplet volume can be estimated by (Equation 1), where Vmax is the droplet maximum value Dn is the outlet diameter, Y is the surface tension, Δp is the difference between the droplet fluid density and the surrounding fluid density and g is the gravitational acceleration 2. Based on the conceptual design (Figure S4,b), we defined a prototype design to test the concept (Figure S4,c). Based on the material readily available on the lab, we defined the prototype.
A flexible PVC tube with an internal diameter of 1.5 mm and 3.6 cm long was used as a base construction. To reduce the internal volume and increase the stiffness on the sensor end three polystyrene pipette tips were cut and inserted in the PVC tube reducing the cross-section. The final pipette tip was cut to produce a droplet with the volume, estimated using equation (Equation 1), less or equal half the volume of fluid displaced from de bulb compression. The prototype (Figure S4,d) total length is 3.6 cm, the bulb length is 1.8 cm resulting in I a bulb volume of 31.8 mm3, the tip diameter is 0.5 mm resulting in a droplet of11.6 mm3 for water.
More information: Hyo-Ryoung Lim et al, Smart bioelectronic pacifier for real-time continuous monitoring of salivary electrolytes, Biosensors and Bioelectronics (2022). DOI: 10.1016/j.bios.2022.114329