How micro-AM produces next-gen precision medical devices

Andreas Frölich, CEO, Horizon Microtechnologies explains how micro-AM produces next-generation precision medical devices.

Recent advances in the precision and accuracy of the micro-additive manufacturing (micro-AM) technology have opened up the use of 3D printing in application areas where its relative lack of precision and repeatability until today had formerly made its use redundant. The technology today is also much speedier, making its use viable in commercial applications. However, micro-AM is somewhat restricted due to the fact that most parts produced on it are made from plastics. This article will review how this limitation can be overcome, and what this means for the use of micro-AM in medical applications, and more specifically in the manufacture of microfluidic devices, microneedle arrays, and miniaturised medical tools. 

Why Micro-AM? 

Micro-AM offers several significant advantages in medical applications due to its unparalleled precision and versatility. One of the primary benefits is its ability to produce highly intricate and complex geometries at a microscale, which is essential for creating devices with the fine details required for some medical applications. Micro-AM enables the production of detailed structures with high accuracy, which would be challenging to achieve with traditional manufacturing techniques. 

In addition, micro-AM is advantageous due to the fact that in more recent times, materials have become available for use on micro-AM machines that have passed the relevant tests for skin irritation and sensitisation, toxicity, cytotoxicity, pyrogenicity, and in vitro haemolysis. They are also sterilisable and are permissible for non-implantable medical applications. Micro-AM also facilitates the customisation of devices to fit specific patient needs, leading to more personalised and effective treatments. The ability to rapidly prototype and iterate designs also speeds up the development process, allowing for faster innovation and time-to-market for new medical technologies. 

Micro-AM plays a crucial role in the consolidation of part production by enabling the integration of multiple components into a single build, thus eliminating the need for complex assembly processes. This capability is particularly beneficial in medical applications, where the precision and reliability of devices are paramount, and it not only enhances the structural integrity and performance of devices but also reduces the risk of leaks or failures that might occur at assembly junctions. This consolidation of parts streamlines manufacturing processes, reduces production costs, and accelerates the time-to-market for innovative medical devices. 

Applications & enhanced functionality  

Horizon Microtechnologies integrates the design and development of 3D microparts with a complete microfabrication production process under the same roof. The company combines its micro-AM expertise with proprietary coating technologies like non-metallic conductive (HMT-Conductive), environmentally resistant (HMT-Protect), and metallic (HMT-Metal). 

These coatings enhance the functionality of microstructures, including plastics and ceramics, driving innovation in applications such as microfluidics, microneedles, and miniaturised surgical tools. 

Microfluidics 

The traditional fabrication of microfluidic devices is often cumbersome due to the need for multiple complex and precise processes such as photolithography, etching, injection moulding, imprinting, and bonding of different materials, which are not only time-consuming but also prone to errors and misalignments, and in the case of bonding an inability to withstand high pressure. These conventional methods require cleanroom environments and sophisticated equipment to achieve the necessary microscale features, making the production costly and less accessible.  

Horizon offers a streamlined solution using micro-AM, integrating the entire fabrication process into a single step followed by coating. This approach enables the design and precise printing of intricate microfluidic structures in a single build, reducing production time and complexity. It supports rapid prototyping and customization of designs, enhancing efficiency and innovation in microfluidic device development. 

Additionally, micro-AM facilitates the prototyping of short-run injection moulding inserts, reducing product development timelines and accelerating time to market. 

Furthermore, Horizon's HMT protect coating can produce a closed layer on microfluidic channel surfaces, whether they are 3D printed, machined, or injection moulded. This separation between the liquid in the channel and the substrate material is advantageous, particularly in enhancing fluid flow for samples ranging from micro-litres to femto-litres. It effectively prevents cross-contamination, crucial for maintaining the integrity and accuracy of results in microfluidic applications where capillary forces or surface tension drive liquid movement. 

For pressure driven microfluidics bonded devices are often inappropriate due to their inability to withstand high pressure as mentioned above, making micro-AM a preferred production technology. 

Micro-needles 

The traditional method of fabricating microneedles, e.g. for transdermal drug delivery, typically involves complex, labour-intensive processes such as lithography (which also requires costly capital equipment), etching, moulding, micro-machining, and laser drilling all of which can be time-consuming, costly, and difficult to scale. These methods also often lack the precision needed to create microneedles with optimal geometries for consistent drug delivery, leading to variability in performance and effectiveness.  

Through the utilisation of micro-AM technology, Horizon provides a solution characterised by precision, scalability, and cost-effectiveness. This technology enables the direct fabrication of microneedles featuring intricate designs and precise dimensions, ensuring consistent quality and performance. Horizon has achieved successful printing of microneedles with internal channels as small as 100 µm. Additionally, the technology allows for the introduction of precise, miniature holes in the needle's side walls. 

Furthermore, Horizon offers coatings such as HMT-Conductive for applications requiring electrical conductivity sensing, and HMT-Protect to optimise fluid flow and prevent cross-contamination between the liquid and the plastic substrate. These enhancements are crucial for maintaining the integrity and accuracy of fluid handling in microfluidic and sensing applications. 

Miniaturised surgical devices 

Horizon has found the use of micro-AM for creating miniaturised surgical instruments crucial due to its ability to consolidate parts and reduce assembly efforts. Traditional manufacturing methods often involve the production and assembly of numerous small, intricate components, which can be labour-intensive and prone to errors. Micro-AM allows for the production of complex, integrated instruments in a single step, minimising the need for assembly and thereby reducing the risk of misalignment or mechanical failure. This integration not only streamlines the production process but also enhances the reliability of the instruments. 

Micro-AM excels in creating geometries that are unachievable with conventional machining techniques, and it enables the creation of intricate structures and fine details necessary for advanced surgical tools. These unique geometries can include internal channels and complex surface textures essential for the functionality of some instruments used in minimally invasive procedures. This capability is particularly beneficial for devices attached to the end of endoscopes or catheters, where space is limited, and precision is paramount. 

In applications where instruments are used inside a patient during operations, the benefits of micro-AM are profound. The ability to produce highly specialised, patient-specific tools enhances surgical outcomes by improving precision and reducing the risk of complications. Instruments such as micro-graspers, forceps, or cutting tools can be custom-designed to fit the anatomical and procedural requirements, ensuring greater efficacy and safety. Additionally, the reduced size and increased functionality of these instruments facilitate less invasive procedures, leading to quicker patient recovery times and reduced healthcare costs.