UNIFEED: An Ultrasonic Milk Homogenizer for Enhancing NICU Nutrition

Introduction: Preterm neonates (24-36 wks of gestation) are incubated in NICUs until developed enough to go home. A critical factor in neonate health and outcome is the nutrition they receive, via mother’s expressed milk. Half of the nutrition in the milk comes from its 5-10% volumetric fat content (Ballard & Morrow, 2013). For best outcomes, the fat content should be delivered to the neonate continuously and uniformly throughout each feed cycle (30 - 45 min long). However, in the current standard of care, the milk fat separates out and accumulates at the top in the enteral syringe during the feed cycle, as a result, it is not delivered to the neonate consistently (Brooke & Barley, 1978). Our goal is to homogenize the milk effectively, providing consistent fat delivery, better feeding tolerance, and fewer interruptions, thus improving neonatal nutrition.
We developed an electromechanical device that has a built-in small-volume ultrasonic homogenizer. A peristaltic pump routes the raw milk through the ultrasonication zone at the appropriate volumetric rate, so that the output milk is fully homogenized i.e. fat globules in the raw milk in the 50 - 100um range are broken down to the 5-10 um range. At this size, the globules remain ‘in-solution’ in the body of the milk and don’t separate out during the feed cycle. An infrared heater warms the milk to 38oC (a universal feed-prep requirement). A microcontroller coordinates pump frequency, enables sampling delivery at different locations, and controls the time delay module for preparing samples at the outlet.

Materials and

Methods: The design of the milk homogenization system integrates five key components: reservoir, pump, chamber, temperature control, and electronics. The reservoir features a recirculation sprayer and one-way valve to maintain fluid integrity. A peristaltic pump ensures contamination-free fluid movement with a controlled flow rate of 2.25 mL/s. The 10ml homogenization chamber uses an ultrasonic probe operating at 28kHz frequencies, crafted from 2024-T351 Aluminum for its suitability in ultrasonic welding and durability. Temperature control is managed by platinum resistance temperature detectors (RTDs), with potential cooling solutions for heat generated by the ultrasonic transducer. The entire system is operated by a Raspberry Pi microcontroller, which coordinates subsystems via a serial user interface and manages power through relays. For iterative testing, the system is mounted on a modular vertical pegboard with aluminum extrusions, facilitating component interchangeability and streamlined data collection (Figure 1b).
We first examine fat particles in milk under a microscope at 1000x magnification, following a method from Wu et al. (2000). We established a baseline by examining minimally processed unhomogenized cow’s milk and conventionally homogenized whole milk. We ran the device with 100mL of raw cow’s milk circulating at 20% pump speed, taking samples at priming, 15, 45, and 90 minutes. We further tested ultrasonic treatment of milk after 15, 45, and 90 minutes sonication and heating, and microscopic images were taken right after the treatment, 5 minutes after, and 10 minutes after the treatment. The size of fat particles was measured using ImageJ through the analysis of the microscopic images.

Results, Conclusions, and Discussions: This project aims to enhance NICU outcomes by improving infant nutrition and addressing global issues of premature births and infant mortality. We created a prototype for non-recirculating measurement of fat particle distribution using non-invasive homogenization. While the prototype design was feasible, challenges in optimizing the sonication time and temperature control arose during prototyping. Despite deviations from specifications, the test bench proved valid and modular.
The results showed particle breakdown starting at 15 minutes, with increasingly smaller particles over time. However, uniform homogenization was not achieved even after 180 minutes, indicating the need for design optimization. We observed reduced particle size 10 minutes after the sonication, compared to the size observed right after the sonication. For a 15-minute sonication and 10-minute waiting time, a 76% reduction of particle size was achieved, while a 79% reduction was achieved with a 90-minute sonication. Therefore, a time-control module can be integrated into the system to minimize the processing time.
Temperature testing revealed that the ultrasonic transducer alone raised the milk's temperature to a steady state of approximately 38°C without additional heating. This range is suitable for NICU facilities (36-37°C). The unintended heating effect, due to inadequate loading on the transducer, could potentially cause damage over time. Future designs should incorporate a heatsink and fan for better cooling while maintaining necessary heating effects. Further testing is required to determine if additional heating or cooling measures are necessary.
In conclusion, our project has made significant strides toward developing a milk homogenization device to improve neonatal nutrition in NICUs. Despite challenges in optimizing the ultrasonic probe and transducer, we successfully created a functional prototype that partially homogenizes milk, ensuring better fat distribution. Initial testing demonstrated the system's potential, with observable fat particle breakdown and suitable temperature maintenance for NICU settings. However, uniform homogenization was not fully achieved, highlighting areas for further design refinement. Moving forward, efforts will focus on optimizing the ultrasonic probe, increasing transducer power, and ensuring the system's affordability and accessibility to address healthcare disparities. With continued development and testing, our device holds promise for enhancing neonatal care and reducing complications associated with premature births.

Acknowledgements (Optional): We would like to thank Dr. Arlene Spilker, PhD, DNP, NP, and Dr. Ish Gulati, MD, Neonatologist, for their invaluable and unwavering clinical feedback and insights, which have greatly contributed to the advancement of this project.