Smaller, Faster, Cheaper: µ3DP for Medical Devices

BY Jason Bassi

This is part 1 of a 2 part blog series focusing on µ3DP and micro injection molding.

Last fall, Medical Product Outsourcing published an article about medtech and micromolding that made me think about the future of µ3DP for medical devices. “Smarter, faster, cheaper. Those three words have become the unofficial motto of medtech development in recent decades,” wrote Michael Barbella in an article from October 2019. Barbella, MPO’s Managing Editor, also interviewed industry leaders as part of a roundtable discussion about the micromolding industry.

In recent years, a growing number of companies have started offering micromolding services. Yet few of these companies are fully focused in this area. Some describe their services as an additional molding capability. Others are contract manufacturers who specialize in microfabrication and have added micromolding to become fully integrated. Regardless, micro molding services are growing because of innovation-driven demand. In short, more medical device companies want “smaller, faster, cheaper”.

For some perspective, consider other trends in both the molding and microfabrication industries. By eliminating runners, molders reduce the waste of expensive molding materials. Five-axis micro CNC machining and micro sinker EDM support micron-level details with accuracy. There have also been automation-related advancements in the handling, packaging, and inspection of micro components. All of these developments are designed to push the limits and reach the goal of “smaller, faster, cheaper”.

Why is Micro Prototyping Missing?

Yet I rarely hear the medical device industry demand “smaller, faster, cheaper” for prototyping and development. Is it because there isn’t a viable solution? Traditional manufacturing methods such as micro injection molding are expensive and time-consuming. Current 3D printing technologies can reduce costs and timelines, but they can’t produce microscale parts with the resolution, precision, and accuracy that’s required. Meanwhile, the demand for medical device miniaturization grows.

Think about the growth in tiny parts like microneedles, septums, sheaths, sensors, microelectronics, and assembled devices. It’s the result of growing requirements for less invasive surgical procedures, point-of-care applications, and advancements in targeted drug delivery, in-vitro diagnostics, implants, and wearable technologies. All of this requires “smaller, faster, cheaper” – and a search for a standard and a technology that can meet this demand.

Micro Components: Working Standard and µ3DP Solution

For many years, I’ve searched for an industry standard that defines the difference between a micro component and a high-precision mini component. I’ve seen and heard a number of different definitions such as shot size, part size, feature size, and tolerances – just to name a few. For the sake of argument, let’s say that a micro component has the following specifications.

  • From microscopic in size to large enough to fit inside a 1” square or diameter
  • Wall thicknesses of .004” (.102 mm)
  • Features like edges and corners within R.001” (.025 mm)
  • Holes as small as R.002” (0.51 mm)
  • Tip radii of R.0002” (.005 mm)
  • Aspect ratios as high as 250:1
  • Tolerances of ±0.0005” (0.0127 mm).

With specs like these, you can see why micro molders are highly specialized. You can also see why many in the industry think that there’s no easy way to prototype microscale components. Until now.

Boston Micro Fabrication (BMF) has developed a patented process called Projection Micro Stereolithography (PµSL) that 3D prints true microstructures with an ultra-high printing resolution (2µm~50µm) and printing tolerance (±10µm ~ ±25µm). BMF’s 3D printers use projection micro-stereolithography (PμSL), a form of stereolithography (SLA) that incorporates a DLP® light engine, precision optics, motion control, and advanced software.

SLA produces parts in layers using a photochemical process. A photosensitive liquid resin is exposed to light so that polymeric cross-linking and solidification occurs. With PμSL technology, a flash of ultraviolet (UV) light causes the rapid photopolymerization of an entire layer of resin. PμSL technology supports continuous exposure for faster processing.

 

Image 1: Blood Heat Exchanger, Spiral Syringe, Cardiovascular Stent (Left to Right)

The BMF microArch S140 System

Table 1 below contains design features and values for the BMF microArch S140 system. As you can see, this PµSL platform can meet the requirements of micro molding. The Recommended column contains values you can achieve with standard printer settings. The Advanced column contains values that may be achievable with the right design and under optimal conditions. BMF can review design and machine considerations with you and provides advanced users with advice about targeted settings.

Design Feature Recommended Advanced
Maximum part size 94 x 52 x 45 mm3
Minimum part size 1 mm3 0.5 mm3
Minimum feature size 0.05 mm 0.01 mm
Minimum hole diameter (vertical) 0.05 mm 0.04 mm
Minimum hole diameter (horizontal) 0.15 mm 0.1 mm
Minimum wall thickness (supported) 0.05 mm 0.02 mm
Minimum wall thickness (unsupported) 0.1 mm 0.05 mm
Minimum unsupported overhang angle 30° 20°
Maximum bridged overhang length 1.5 mm 5 mm/10 mm (rigid material)
Maximum non-bridged overhand length 0.3 mm 0.5 mm
Aspect ratio for channels 100:1 500:1 for > ø 0.1 mm
Aspect ratio for pins & pillars 40:1 100:1 for > ø 0.1 mm
Minimum feature clearance 0.1 mm 0.05 mm
Recommended channel shape > ø 100 µm rectangular or circular
Recommended channel shape < ø 100 µm circular
Part-to-part spacing 0.1 mm 0.05 mm
Layer height 0.01 – 0.05 mm
Support structure shape cone
Support structure cone top diameter 0.08 – 0.2 mm
Support structure cone base diameter 0.1 mm – 1mm

Table 1: microArch S140 Design Features and Values

PµSL Powers µ3DP for Medical Devices

PµSL technology from BMF provides a demonstrated solution for the prototyping and development of medical devices and components at the microscale. Today, BMF is also seeing a growing number of applications where PµSL technology can be used to cost-effectively manufacture end-use components. Even more opportunities will arise as the material properties and production speeds improve.

Would you like to learn more about µ3DP? Contact BMF to discuss your application.

Interested in learning how Accumold uses PµSL technology for prototyping? Read part 2 here.