Intelligent medical designs target varied aims

Designers must tackle many issues in an industry to which people entrust their health and, at times, their lives. First and foremost, medical products must perform their functions both reliably and safely. In addition, they must conform to the economic realities in the current health-care system by helping to reduce costs. Finally, products with aesthetic and ergonomic appeal can make a world of difference in comfort levels and in the marketplace.

Faced with these sometimes conflicting requirements, two medical OEMs recently sought help from Ecco Design Inc., an industrial design and product development firm. The New York-based company has a special talent with plastic part design, due partially to principal Eric Chan's 15 years of experience in the plastics industry.

Chan, along with designers Fede Carandini and Jeff Miller, recently completed two medical projects with flying colors. In both cases, the input from Ecco addressed cost, performance, and aesthetics: goals aimed at market success.

Modular Instrument Design
Working with Dentsply International, the largest global producer of ultrasonic dental scalers, Ecco helped update a line of equipment called SPS Scalers and create a new product called the DualSelect Solution Dispenser (Figure 1). The dispenser works with the scaler to deliver medicated solutions. Previously, scalers could only deliver tap water, so dentists had to jury-rig tubes and containers to supply any other liquid. In addition to working independently, the new dispenser couples with any brand of scaler, houses all components, and readily accepts available standard bottles containing medicated solutions. Both products werdesigned for disassembly, with 85 percent of the plastic components marked for recycling classification.

To cut tooling costs, all SPS scalers use a modular housing molded in modified PPO (mPPO) for chemical resistance to blood, medication, and steam sterilization. Different models contain dissimilar internal components, but the housing design accommodates all of them. Also, the three-part housing incorporates several fastening features that had to be assembled in the former design. Ecco's design team also added interlocking features, allowing the three parts to be assembled with only one screw.

For the dispenser housing, also molded in mPPO, designers used a two-shell construction combined with nontraditional molding angles. "This allows the main housing component to be molded in one shot, eliminating assembly steps normally required to fasten the 'floor' of the box to the rest of the housing," says Miller. The front shell contains two angled areas for bottles, which allowed Ecco to design the back shell--a roughly L-shaped piece--with an angle less than 90°. As a result, the back shell could then be molded in one piece.

Within the dispenser is another innovation designed to reduce part count. To ensure that pressurized air and liquid cannot build up unless the polycarbonate shield is closed, Ecco included a safety interlock. Any accidental spill or pressurized release will be contained behind the shield. To activate the interlock, Ecco designed a tapering rib into the clear polycarbonate shield, eliminating the need for another part and making the safety interlock activation user friendly. Notice also the three 'scoops' designed into the top of the scaler (Figure 1). These depressions not only hold the handpiece but also let the dispenser connect and sit on top of the scaler to maximize counter space.

Solid modeling via Pro/E (Parametric Technology) helped Ecco cut its customer's production lead times from 14 to 6 months on this project, says Chan. Scaler sales jumped 45 percent over similar existing products, and U.S. sales for the new dispenser were three times Dentsply's original expectations. In Europe, a new market for the company, sales exceeded projections by 500 percent.

Leg Walker Simplified
Johnson & Johnson Orthopaedic designers wanted to update the first generation of leg walker products. For those unfamiliar with orthopedics, leg walkers are bracing devices used to treat stable ankle fractures, sprains, and other minor injuries to the foot and ankle. Competing products were cumbersome to remove and install as well as being difficult to fit correctly. They provided either stability in a resting position or good curvature for rocking the leg when walking, but never both. They were also aesthetically unappealing, a real minus for gear that patients had to wear in public for as many as six weeks.

Finally, the three-part walkers were costly to manufacture because of the number of parts necessary to provide adjustment and flexibility. These extra items included die-cut and thermoformed straps that tangled easily.

Solving these challenges required a drastic departure from the traditional look of leg walkers. Ecco's design for the Nextep Contour Lower Leg Walker addressed issues of lower manufacturing cost, improved walking and standing performance, simpler installation and removal, and high aesthetic appeal (Figure 2).

Manufacturing costs were lowered in two ways. First, Ecco and J&J chose an unfilled polypropylene for the walker's shell and a TPE for the sole. Former walkers used higher-priced engineering thermoplastics. Second, the new design uses only two molded parts for the shell. Older designs used three, increasing tooling costs. Also, the shell parts can be used for either right or left legs, eliminating additional parts and related tooling.

By reducing the shell to two parts, the new design also makes installation, removal, and fit easier while the molded-in articulated area in front (Figure 3) provides flexible adjustment to allow for different leg sizes and shapes. A simplified fastening system consists of shorter straps that are adjustable with one hand. Increasing the material thickness at the heel and other areas provides both flexible and rigid areas within the same part. For the TPE sole, designers optimized curvature so patients can easily rock the foot for comfortable walking. The sole is also wide, with a low profile, for balance and safety.

Aesthetically, the lined surface pattern makes the walker visually lighter and more appealing. Rather than having a medical look, the Nextep has the appearance of sports gear. Ecco's team considered the fact that most patients wearing the walker are dealing with sports-related injuries. Six oval-shaped vents not only provide cooling and drying functions but also improve the look of the walker.