Photonics of the future

A new generation of medical devices might be closer than people imagine. Until recently, wireless medical devices were futuristic solutions, but today all kinds of sensors are deeply integrated into the average person’s daily life. Indeed, the applicability of consumer electronics shows that novel medical devices do not always require the development of brand new technology. Rather, progressive technological advancement, miniaturisation and integration are enabling new solutions for a wide range of medical disorders and diseases.

Microfluidic devices for diagnostics and testing, stem cell differentiation and maturation control, surfaces with antibacterial or hydrophobic properties, and dental, hip and knee implants, along with spine plates with cell-guiding properties – these are a few of the many functionalities that can be achieved using lasers for surface micro and nanostructuring. Additionally, laser texturing introduces manufacturing benefits like risk and cost reduction, alongside numerous design advantages. Laser surface structuring can be achieved by either thermal or non-thermal processes.

More traditional thermal processes increase the absorption of laser radiation and remove unnecessary material through vaporisation or thermal decomposition. However, these processes can also lead to melting or thermal degradation of the material. Modern ultra-fast lasers allow non-thermal processing to obtain the same results without undesirable thermal effects. For implants in particular, surface topography can markedly influence biological responses such as cell adhesion, cell orientation and cell motility, all of which ultimately impact interactions with tissue. Companies such as Microrelleus, along with several EU initiatives for the production of functionalised metallic surfaces, are focusing on using laser surface structuring to precisely design and alter surface topographies and ensure implants deliver the best clinical outcomes. For example, Laser4surf, FemtoSurf and others are developing solutions for improving the osseointegration of medical implants and reducing their long-term failure rate. These approaches to supporting integration by tissue ingrowth can enhance the mechanical stability of implants.

A big challenge associated with medical implants or intravascular devices is the risk of bacterial infection and biofilms. These can lead to implant revision surgery. To reduce the risk of infection, hospital environments must be made as antiseptic as possible, ideally by using materials that inhibit the fixation of bacteria and avoid the formation of bacterial biofilms.

The level of bacteria adherence depends directly on the physical and chemical composition of the surfaces. As such, while antibiotics and antibacterial coatings are used to reduce infection risks, surface structuring offers an alternative (or additional) solution. Surface structures comprising spikes, laser-induced periodic surface structures (LIPSS) and nano-pillars can reduce bacterial retention by up to 99%. A system based on multi-beam processing techniques, enabling direct laser interference patterning to create LIPSS, is being developed within the EU-funded project LAMpAS. Using high resolution (200nm–200μm) and thin-diskbased ps-lasers delivering up to 1.5kW at MHz-level repetition rates, LAMpAS offers a complete laserbased surface-texturing system solution aiming at high throughput (up to 1–5m2/min) manufacturing of antibacterial surfaces. Given the advantages they bring in fighting bacteria and lessening the need for antibiotics, laser micro and nanostructuring will become more widely used within healthcare in the coming years. The reliability and development potential of laser technology makes it a very promising technology to sustainably tackle such issues.

Lasers for surgery

Depending on the wavelength, medical lasers can be used for ophthalmologic surgeries, photodynamic therapies for cancer, cosmetic and dermatological treatments, dental procedures, general surgery, cardiovascular photoablation and more. Each procedure has its own set of requirements and technical parameters. For surgical systems, the pulse duration could range between nanoseconds and milliseconds depending on the types of pulse and operations. The spot-size also has to be minimised to prevent damage to the surrounding tissue. However, dermatological applications that target deeper layers of the skin require larger spot sizes and, in such cases, flat-beam lasers are preferred over those with Gaussian beam profiles.

In all of these applications, lasers offer multiple advantages. Not only are they precise and fast, but the heat produced during laser activation can act as a steriliser, reducing the risk of infection. Furthermore, laser heat seals blood vessels, resulting in less bleeding and swelling, and potentially speeding up recovery. In general, medical procedures exploiting lasers are also less time-consuming and minimise damage to healthy tissue due to the reduction of the required incision size. On the other hand, laser systems are currently still not fully accepted among the medical community. The use of lasers requires additional training, and strict safety precautions make some medical staff reluctant to make use of the technology. Additionally, laser equipment is often bulky and expensive, and not all health insurance providers cover procedures performed with lasers.

Biolitec, DEKA Medical, Fotona, LISA Laser, Modulight, NKT Photonics, Philips, Quanta and many other companies are devoted to changing that by further improving lasers and systems for surgical, dermatological, and other applications. Future laser technologies for medical applications will reduce the cost and size of the equipment. Additionally, laser surgery tools could acquire extra sensing functionality – for example, by optical spectrometry. Such auxiliary features could lead to the development of a ‘smart knife’ to cut out diseased tissue without so much as touching the healthy tissue surrounding it.

Medical imaging techniques such as spectroscopy, optical coherence tomography (OCT) and photoacoustic imaging can also be integrated as supporting techniques during diagnostics, surgery and other decision-making steps in clinical practice. For all these imaging techniques, laser sources play a vital role in data acquisition. Indeed, NKT Photonics’s SuperK supercontinuum white light laser can be found in multiple medical imaging devices.

Equally, the new OCT device introduced by DAMAE Medical uses it to detect skin cancer faster, more costeffectively and without the need for biopsies. Innolas’s robust, fibre-coupled lasers are also integrated in the multispectral optoacoustic tomography system developed and produced by iThera Medical, which can image nearly every region of the body. The first clinical multicentre study for using it to image inflammatory bowel disease is scheduled for the near future.

Another solution using Raman spectroscopy for in vivo skin analysis is offered by RiverD International. It is widely used in product development and clinical testing in the personal care industry, and is turning heads in the pharmaceutical industry due to its unique capability to quantitatively determine the in vivo penetration of materials applied to the skin.

In a combined effort with art photonics and Erasmus University Medical Centre, RiverD is also supporting SurGuide, the Raman-based technology of which will enable inspection of resected tissue during surgery to determine if a tumour has been completely removed in real time. Many other medical imaging techniques are currently being tested for integration into future medical devices for surgery guidance and other medical applications.

For digital health

Currently, most diagnostic tests and physiological monitoring tools are limited to the short-term detection of parameters in the clinical environment. That said, in many cases, continuous measurement of multiple parameters simultaneously over days or weeks of daily life is required for effective diagnosis or the monitoring of recovery after a treatment. On top of that, the personalisation of medical diagnosis and treatment has a growing role in the advancement of healthcare.

The successful implementation of such novel approaches demands, on the one hand, reductions in the complexity, size and cost of instruments and, on the other, faster and more reliable data. Photonics is a key enabling technology in medical sensors and devices, allowing continuous non-invasive monitoring.

For instance, imec has shown that by leveraging the advantages of optical principles with CMOS processing, silicon photonics could revolutionise medical diagnosis. The company’s spectroscopy approach for continuous glucose monitoring, its integrated six-beam homodyne laser Doppler vibrometry system for early detection of cardiovascular diseases, and its on-chip cell-sorter with an integrated lenseless camera are just a few examples. Imec’s spin-off, Spectricity, provides a complete spectrometer the size of a photodiode.

Many hospitals worldwide are already adopting sensor technologies for improved patient care. Wireless sensors help patients with disabilities live without having to make frequent visits to the doctor. In people with heart disease and diabetes, heart activity and glucose levels can be monitored to automatically alert the doctor when there is a problem.

Heart rate and pulse rate measurement technology has come a long way – from strap-on-the-chest solutions to an accurate optical heart rate monitor that takes measurements straight from the wrist. The convenient usability and performance of optical heart rate monitors is the result of long-term scientific research, both on the technology side and on the physiological side. Polar Precision Prime incorporates unique sensor fusion technology and processes information using an algorithm to provide accurate heart rate and pulse rate readings, even in the most demanding conditions. It solves one of the biggest shortcomings of previous wrist-based optical heart rate monitoring devices: inconsistent data from excess movement. And, while currently most medical wearable devices address diabetes, cardiovascular and respiratory diseases, the list of possible applications and benefits of wearable devices is nearly endless. For instance, one could combine behaviour monitoring with weather and pollutant tracking, enabling physicians to accurately assess individual health risks.

The development and production of wearable medical devices requires a combination of expertise from many different fields. Just within photonics, the ecosystem is very scattered, which is a major challenge for end-user companies and manufacturers. Furthermore, the strict regulations within the medical sector slow down the introduction of new solutions. MedPhab’s pilot production line is addressing these challenges and will accelerate the commercialisation of diagnostic devices and instruments for treatments based on photonics with reduced costs. MedPhab’s high-quality infrastructure and extensive know-how is complemented with a globally unique ability to ensure operation in medical settings meets regulations.

Medical sensors, point-of-care devices, medical wearables, smart scalpels and the integration of medical devices with robotic technologies, augmented reality and AI are critical steps towards a new era of digital medicine. Though telemedicine is only just finding its feet, remote monitoring, tracking and consulting are indisputably the future of healthcare, and the future’s arrival is being tremendously accelerated by the present Covid-19 pandemic.

Development of future medical devices involves not only sensor makers and medical wearable manufacturers, but also IT companies, including network, cloud computing, software and AI developers. Lasers are absolutely vital to these developments, from the largest data throughput requirements down to so-called ‘tiny AI’, which is integrated on to a chip.

These views are the author’s own and do not reflect the views of the European Commission or Photonics 21. The projects mentioned have received funding from the EU’s Horizon 2020 research and innovation programme.