Cataract surgeries using phacoemulsification (phaco) are standard practice, accounting for the large majority of all cataract surgeries. Reliance on sterilization processes has significant environmental implications, giving its energy and resource intensive nature. This thesis introduces a novel hybrid phaco handpiece design, eliminating the need for sterilization by adding a disposable to facilitate sterile use, combined with a reusable as driver of ultrasound. This product is the first step towards a proposed fully circular system. This project has a focus on reducing impact, while maintaining phaco functionality; it does so by testing for phaco ultrasound characteristics and functioning fluidics while addressing the challenges associated with sterilization. The design emphasizes quick, secure, and sterile assembly in the operating room (OR) while maintaining cost-effectiveness and minimizing environmental impact. The hybrid phaco handpiece achieves its functional design by carefully managing the components responsible for ultrasound and fluidics. The internal sonotrode, driving ultrasound, is split between the disposable and reusable components, connected securely through a threaded interface. Fluidics are managed by splitting off before reaching the reusable part, employing a simple yet effective O-ring design in the disposable product. Maintaining sterility in the OR is a critical aspect of the hybrid phaco handpiece design. Mechanical seals in O-rings provide internal sterile barriers, and a blister pack facilitates sterile interaction between non-sterile and sterile components. The contact-free assembly of the disposable into the reusable ensures a tight connection, validated by a torque ridge that breaks at a specified torque, offering a visual cue for successful connection. This usability design, validated with healthcare professionals, adds safety and fits the quick nature of cataract procedures. The innovative sterile handover method is implemented through the packaging itself, acting as a sterile barrier between different nurses handling the disposable and reusable components. During handover, a pre-attached sterile tube sleeve is unrolled over the non-sterile component. This ensures a seamless and sterile transition during assembly, minimizing the risk of contamination. A comprehensive functional analysis validates the hybrid design, ensuring it meets specifications. Insights gained from this analysis guide further mechanical tuning, particularly in aspects influencing ultrasound characteristics. Beyond functionality, the hybrid phaco handpiece design has environmental implications. By eliminating the need for energy-intensive sterilization procedures and reducing waste from disposable wraps, the design reduces its climate impact by 67% over the entire life cycle. This hybrid phaco handpiece design represents a step towards a circular system in the field of cataract surgeries. Balancing functionality, sterility, and environmental impact, this novel approach not only provides new insight into sustainable phacoemulsification procedures, but also shows the potential of hybrid reusable and disposable products in healthcare.