Nanopatterning for medical applications

Nanotechnology appears in popular culture as a cure for everything from cancer to balding. In science nanotechnology is an umbrella term for a variety of structures and molecules used in optics, MEMS, materials, chemicals and some biological systems.

In this new blog series, we shall explore nanopatterning (the engineering of nanoscale structures on surfaces), its prevalence in nature, manufacture and application to medical devices.

Drawing inspiration from nature

Figure 1 – Sunset moth scales macro by Johan J.Ingles-Le Nobel, Cropped, CC BY-NC-ND 2.0

Nanoscale structure plays a fundamental role in numerous biological systems, and in some cases has developed to aid an organism’s survival and proliferation. Nanostructures can impact on the wetting and optical properties of a surface as well as their molecular interactions. Adjusting the spacing and morphology of these structures can change how they behave in contact with solids, liquids, biomolecules and how they catalyse certain chemical reactions. Organisms rely on these structures to stay clean, aid communication, and promote or prevent adhesion. The presence of ordered micro- and nanoscale structure appears to the human eye as iridescence created by the selective scatter of certain wavelengths of light.

Dry adhesion

While the exact mechanisms of adhesion differ, the feet of various tree frogs, insects and lizards rely on nanoscale and microscale structure to cling to and climb vertical or inverted surfaces. Perhaps the most famous climbers that rely on adhesion are geckos. Gecko climbing ability comes from millions of hair or setae on their feet which experience Van der Waals interactions with the substrate [1]. Individually the interactions are weak but collectively give the gecko the adhesive force necessary to hold up to four times its own weight. These setae evolved from tiny hair-like growths present on the bodies of all geckos [2]. Generating setae involves lengthening these hairs and splitting the tips to produce micro- and nanoscale hierarchical structures. Curiously, researchers have found that several gecko species developed these adhesive abilities independently when faced with an environment where climbing aided survival, losing them again over time when the environment changed [2].

Figure 2 – Gecko’s secret power by Matteo Gabaglio, Annotation, Order, CC BY-SA 3.0

In the last 20 years, the adhesive strength, reusability and non-fouling properties have attracted increased interest in gecko-inspired adhesives. Manmade micro- and nanoscale hierarchical patterns produced by embossing, casting or roll-to-roll printing have resulted in several tape and patch analogues. As popular as this topic has been, it has not been without its challenges. In addition to difficulties in manufacturing, gecko mimetic adhesives experience poor adhesion to wet and contaminated surfaces [3]. Water disrupts the surface interactions which is also the reason why PTFE (which exhibits weak Van der Waals dispersion forces) is one of few materials that a gecko can’t climb on [4].

Wet adhesion

For wet adhesion it makes more sense to look to water dwelling organisms. Mussels create an adhesive containing a tyrosine residue called DOPA, which has seen increased attention. DOPA and similar coatings are key to allowing nanopattern based adhesives to work in wet conditions. The structure of DOPA allows mussels to form strong and reversible bonds with a variety of substrates [5]. Mussels use this to anchor their pads to rocks and withstand significant punishment from tides and currents. Researchers have so far used DOPA and analogues in an attempt to develop improved surgical adhesives, particularly for amniotic sac repair[6]. Some have combined this with the gecko adhesive above to produce all-purpose hybrids named “Geckel” [7]. These hybrid surfaces consist of a microstructure coated in mussel mimetic adhesive to achieve adhesion in wet or dry conditions. As with any novel technology, achieving a robust product and scalable process has likely limited its implementation. Alternative adhesive-free-adhesives for wet conditions look to the octopus for inspiration. Although an octopus sucker is far larger than the other features we have discussed, its design has been the inspiration for many micro- and nanoscale mimics. Octopodes use suckers as muscular-hydrostats where the internal volume is increased to generate low pressure (≤ 2.7 bar below ambient pressure when submerged) [8]. The octopus vulgaris differs from other species in that it utilises a ball in cup morphology to maintain adhesion and resist shear [9].  Its unique morphology creates two regions of low pressure with the ball protrusion sealing the two volumes and mechanically locking the sucker configuration.

Figure 3 A.) Suckers of octopus by Steve Lodefink, Suckers of octopus by Steve Lodefink, CC BY 2.0. B.) Illustration of sucker adhesion mechanism of Octopus vulgaris.

Octopus mimetic surfaces produced by vacuum casting use microscale suction cups (~ 100 μm) with a similar ball in cup morphology to generate suction [10]. This approach has seen some applications targeting skin but so far appears limited to working on flat surfaces and generating relatively weak vacuums. Some commercial materials such as REGABOND micro-suction foam are aimed for the general consumer market and work on a similar principle [11].

Repulsion

Some plants use micro- and nanoscale texture for an alternative purpose, the “lotus effect” being the most famous example. The lotus effect arises from the ability of micro- and nanostructures to amplify the natural tendency of a surface, making hydrophobic materials superhydrophobic. A lotus leaf has arrays of hydrophobic waxy hierarchical micropillars on its surface [12]. The high roughness and low contact area of these pillars forces water droplets to adopt a Cassie-Baxter state where air is trapped below the fluid meniscus. To reduce the Gibbs free energy of the system the water droplets adopt a highly rounded shape. This allows them to slide off and pick up dirt in the process, keeping the leaves free of debris. The springtail takes this effect further with a cuticle that has a re-entrant or overhanging surface structure [13]. These structures resemble nanoscale mushrooms which pin the fluid line to prevent even low surface tension fluids from fully wetting the surface in what is referred to as oleophobicity. The springtail uses this for survival creating an air trap around its body when submerged. Both superhydrophobicity and oleophobicity are found in industry, often finding use in semipermeable membranes and self-cleaning coatings. The surface energy and morphology of the of the coating material dictate the degree of nonwetting. These structures are still vulnerable in high pressure applications where the structures or the film of air can collapse.

Figure 4 – The springtail cuticle has been used as inspiration for manmade re-entrant omniphobic surfaces A.) Springtails. B.) Springtail submerged in water. C.) Springtail submerged in oil. Scale bars: 1 mm. Image from R. Hensel et al. [13], CC BY-NC 3.0.

A very different, and potentially more robust approach is used by the pitcher plant. In these plants a microporous surface is used to retain a lubricating fluid film. The films are created when water or nectar becomes locked into microscale textures in the surface of the plant creating a continuous layer of lubrication. The film is immiscible in the oil on the insect’s feet resulting in a surface that easily shears away on contact and very low friction. Unlucky insects which land on the plant’s lip end up sliding down into the plants digestive fluid to become a snack. The film is replenished by capillary effects which redistribute fluid across the film surface. The advantage of this arrangement is the immiscible fluid is incompressible unlike the air used by the lotus leaf and allowing it to serve in higher pressure applications.

Figure 5 A.) Sarracenia pitcher anatomy by Noah Elhardt, Sarracenia pitcher anatomy basic, marked as public domain. B-E.) Microstructure of N. gracilis waxy surfaces. Scale bars shown. Image from Bauer et al. [14], CC BY 4.0.

Pitcher plant mimetic surfaces have been named “slippery liquid-infused porous surface(s)” or SLIPS. These surfaces can be tailored and often use a lubricant which is immiscible in the target substance. The porous substrate consists of open interconnected pores to retain the lubricating fluid. While evidence of industrial application is limited, it is a promising route to stain-resistant coatings for optics.

Optical effects

Certain organisms use micro and nanostructures to produce iridescence that makes the rest of the animal kingdom pale by comparison. While many rely on chemicals for coloration, using microscale structures is called structural coloration or physical colour. Butterflies use this effect for visual communication to find mates or scare away would-be predators. The most famous example is the Morpho butterfly native to Latin America [15]. The Morpho is an underwhelming (but well hidden) shade of brown with its wings closed but a bright iridescent blue when they open. The blue iridescence comes from tiny chitin gratings on the surface of a butterfly’s wings [3]. The layering of these structures causes diffraction and constructive interference of visible light waves according to Bragg’s law, producing the visual perception of a very intense colour [17]. The angle at which the butterfly is observed changes the colour we perceive the wings to be, shifting from blue to copper when viewed at an angle. The papilionidae family of butterflies use similar architectures combined with fluorophores to harvest NIR light to create luminescence [18].

Figure 6 – A.) Blue morpho butterfly by Gregory Phillips, Blue morpho butterfly, CC BY-SA 3.0. B.) Nanoscale Structures on a Blue Morpho Butterfly Wing Image from Potyrailo et al. [19], CC BY 4.0.

The unique physical, chemical, and optical properties of these structures have led to interest in several industries. Extensive research and development efforts have gone into mimicking these effects for energy harvesting, sensing and photocatalysis [19]. For medical applications they have a role to play in optical biosensing. By coating a grating in environmentally responsive molecules or hydrogels an optical indicator can be constructed. Structures such as this have been coined hydrogel-actuated integrated responsive systems (HAIRS)[20].

We hope that this has been an interesting read. The next edition will discuss the practicality of fabricating these structures, and their suitability for parts used in medical devices.

If you have any questions about micro engineering and smart surfaces, please do not hesitate to get in touch or find me on LinkedIn.

Bibliography

[1]        K. Autumn and N. Gravish, “Gecko adhesion: evolutionary nanotechnology,” Philos. Trans. R. Soc. A Math. Phys. Eng. Sci., vol. 366, no. 1870, p. 1575 LP-1590, May 2008.

[2]        T. Gamble, E. Greenbaum, T. R. Jackman, A. P. Russell, and A. M. Bauer, “Repeated origin and loss of adhesive toepads in Geckos,” PLoS One, vol. 7, no. 6, 2012.

[3]        A. Y. Stark, T. W. Sullivan, and P. H. Niewiarowski, “The effect of surface water and wetting on gecko adhesion,” J. Exp. Biol., vol. 215, no. 17, p. 3080 LP-3086, Sep. 2012.

[4]        A. Y. Stark et al., “Adhesive interactions of geckos with wet and dry fluoropolymer substrates,” J. R. Soc. Interface, vol. 12, no. 108, p. 20150464, Jul. 2015.

[5]        J. H. Waite, “Mussel adhesion – essential footwork,” J. Exp. Biol., vol. 220, no. 4, p. 517 LP-530, Feb. 2017.

[6]        M. Perrini, D. Barrett, N. Ochsenbein-Koelble, R. Zimmermann, P. Messersmith, and M. Ehrbar, “A comparative investigation of mussel-mimetic sealants for fetal membrane repair,” J. Mech. Behav. Biomed. Mater., vol. 58, pp. 57–64, 2016.

[7]        H. Lee, B. P. Lee, and P. B. Messersmith, “A reversible wet/dry adhesive inspired by mussels and geckos,” Nature, vol. 448, p. 338, Jul. 2007.

[8]        J. J. Wilker, “How to suck like an octopus,” Nature, vol. 546, p. 358, Jun. 2017.

[9]        F. Tramacere, L. Beccai, M. Kuba, A. Gozzi, A. Bifone, and B. Mazzolai, “The Morphology and Adhesion Mechanism of Octopus vulgaris Suckers,” PLoS One, vol. 8, no. 6, p. e65074, Jun. 2013.

[10]      S. Baik, D. Wan Kim, Y. Park, T.-J. Lee, S. Ho Bhang, and C. Pang, “A wet-tolerant adhesive patch inspired by protuberances in suction cups of octopi,” Nature, vol. 546, pp. 396–400, 2017.

[11]      “materialdistrict.com.” [Online]. Available: https://materialdistrict.com/material/regabond-s. [Accessed: 05-Sep-2018].

[12]      T. Darmanin and F. Guittard, “Superhydrophobic and superoleophobic properties in nature,” Mater. Today, vol. 18, no. 5, pp. 273–285, 2015.

[13]      R. Hensel, C. Neinhuis, and C. Werner, “The springtail cuticle as a blueprint for omniphobic surfaces,” Chem. Soc. Rev., vol. 45, no. 2, pp. 323–341, 2016.

[14]      U. Bauer, B. Di Giusto, J. Skepper, T. U. Grafe, and W. Federle, “With a Flick of the Lid: A Novel Trapping Mechanism in Nepenthes gracilis Pitcher Plants,” PLoS One, vol. 7, no. 6, p. e38951, Jun. 2012.

[15]      Y. Ding, S. Xu, and Z. L. Wang, “Structural colors from Morpho peleides butterfly wing scales,” J. Appl. Phys., vol. 106, no. 7, pp. 1–6, 2009.

[16]      R. Yan et al., “Bio-inspired Plasmonic Nanoarchitectured Hybrid System Towards Enhanced Far Red-to-Near Infrared Solar Photocatalysis,” Sci. Rep., vol. 6, no. December 2015, pp. 1–11, 2016.

[17]      S. Zhang and Y. Chen, “Nanofabrication and coloration study of artificial Morpho butterfly wings with aligned lamellae layers,” Sci. Rep., vol. 5, pp. 1–10, 2015.

[18]      E. Van Hooijdonk, C. Vandenbem, S. Berthier, and J. P. Vigneron, “Bi-functional photonic structure in the Papilio nireus (Papilionidae): modeling by scattering-matrix optical simulations,” Opt. Express, vol. 20, no. 20, p. 22001, 2012.

[19]      R. A. Potyrailo et al., “Towards outperforming conventional sensor arrays with fabricated individual photonic vapour sensors inspired by Morpho butterflies,” Nat. Commun., vol. 6, p. 7959, Sep. 2015.

[20]      J. M. J. den. Toonder and P. R. Onck, “Artificial cilia.” Royal Society of Chemistry, Cambridge, 2013.

What does ‘rapid’ really mean?

One of the real strengths of working with a consultancy is the ability to increase the size of your team, bring in extra skills and get a project off the ground very quickly.  When you’re behind schedule on a market launch, regulatory submission, or faced with an unexpected verification test failure or recall, this speed can be the difference between successful and unsuccessful outcomes for your project.

So what does ‘rapid’ actually mean?  How fast is fast?  Let’s illustrate with an example of a project Springboard completed recently:

One Wednesday, we received a call from a client already known to us, asking us for help with an urgent problem.  This would require a mix of literature-based scientific research and practical testing in the lab.  Results were needed as quickly as possible, and certainly in time for a meeting three weeks later.

Springboard pulled out all the stops to plan the project and write a detailed proposal within two days, submitting this to the client on Friday morning.  The client was able to send written authorisation the same day, and put parts in the post for next day delivery.

The project leader briefed his team at 10 am on Monday morning.  The team – comprising two PhD-level scientists and a graduate engineer, with technical oversight from one of Springboard’s directors – hit the ground running.  Devices were disassembled and testing began before lunchtime.

The first update call to the client was delivered at lunchtime on Thursday.  This was a 30-slide PowerPoint presentation rich in technical detail, all of which was backed up with either laboratory experiments or cited academic papers.  In discussion with the client’s team members, we agreed the priorities for the next week of research.

Two more updates were delivered before the client’s original deadline, and the client went into their meeting briefed and confident.  A 42-page report, backing up all of the observations and conclusions drawn with full references, followed a week later.

Project timeline

Two days to plan and propose a project.  One week to deliver first results.  One month to deliver a complete project yielding real technical insight to drive policymaking.  No ongoing commitment.  A real illustration of how an agile consultancy can react much faster than a large corporation, and so add real value to urgent development and troubleshooting projects.

Consultancy or manufacturer?

Let us suppose you need a new product developed.  You have 3 choices:

  1. Develop the product entirely in-house.
  2. Contract a consultancy to develop the product for you.
  3. Contract a manufacturer to develop the product for you.

In the past, companies would develop products themselves, entirely in-house.  In recent years, that model has become less common as companies have reduced their internal R&D teams and looked for collaboration to bring new products to market.

In some markets, engineering and design consultancies have delivered development projects as a service.  More recently, manufacturing companies have hired development engineers and set up development labs.   This article discusses the pros and cons of each method.  If you would like to know more, or have any feedback, do not hesitate to get in touch.

Development strategy Pros Cons
In-house
  • Knowledge stays in-house.
  • Limited IP leakage (other than employees leaving, indiscretions etc.).
  • Lower cost if, and only if:
    • Team and facilities are already in place, and
    • Recruitment, training, site and maintenance costs are not in your budget, and
    • Your team is fully utilised on productive projects at all times.
  • Limited to the skillset of the existing team.
  • Psychological inertia due to historical products and constraints.
  • Large expense of keeping the team when they are not fully utilised.
Consultancy
  • Highly skilled people available. This can make all the difference between a device passing tests and getting to market on time, or languishing in endless cycles of fire-fighting modifications. Removing even one redesign-revalidate cycle can easily save far more money than using a low-fee-rate manufacturer.
  • Flexible team structures.
  • Best option for an impartial view of which technologies would work best.
  • Impartial as to which manufacturer to use: consultancies are the best option if you intend to have more than one manufacturing source for risk mitigation.
  • Some consultancies, particularly those that specialise in your industry, will have relevant up-to-date experience from other projects.
  • Can have high fee rates (particularly those with > 100 employees).
  • Might not have experience in manufacturing. You can ask who will be working on the project, and what their experience is.
  • Consultancies with internal projects might save the best ideas for themselves. Springboard does not have internal projects.
Manufacturer
  • Fee rate can appear lower than consultancies.
  • Sometimes, deep knowledge of a given manufacturing process.
  • Good at making incremental changes to existing products, but not at innovating new products.
  • It will be very difficult to transfer manufacture to another party because the design will be optimised
    for their processes, and there will be no documentation or data necessary for transfer to another company.
  • Manufacturing costs will be high because they will need to recover their costs and make more profit than otherwise to make up for Net Present Value, and their risk.
  • Most manufacturers are trying to build up their own IP portfolio. This might mean they save the best ideas for themselves, or put some of their IP into your product.
  • Limited to the skillset of the existing team.
  • Psychological inertia due to knowledge of their existing processes. For example, if the company is very experienced with aluminium tooling, can you guess what your tools will be made from, even if steel tooling would have been a better option?

How to find the best contract R&D partners

“Most of us understand that innovation is enormously important.  It’s the only insurance against irrelevance”

Gary Hamel

“Innovation requires the ability to collaborate and share ideas”

Bill Gates

Innovation is critical to all businesses. We live in a knowledge-driven economy and, especially in medical devices and drug delivery, giving patients the benefits of new and better products is clearly beneficial for all concerned: patients, payers, healthcare authorities, pharmaceutical companies, and medical device manufacturers.

Collaboration is more important than ever to manage technical risks and build on the best talent available throughout the development process.  But there are very few sources of good information on how to find the best companies to collaborate with.  This article gives an insight based on many years of experience in the field.

We hope that it is helpful and perhaps even interesting!

Working together

Step 1: Consider the pros and cons of working with external experts

Collaborating with external experts works best when you and the relevant stakeholders within your organisation (particularly the development team) see the value.

In some cases, there’s reluctance to collaborate, but it can lead to projects not working very well due to the limits of the skills, capability and equipment of your own development team.

In other cases, where you just want more people in your office or labs to work under your own supervision, a lone contractor may be more appropriate than an external R&D partner. Using contractors is a different mind set from working with external R&D companies because typically the latter will take on leadership to overcome hurdles in the way, and display a greater degree of autonomy on reaching a solution.

It is misleading to compare quotes to salaries. This is a common temptation, but when you consider the salary of yourself or your staff, you are not including pension, bonus, National Insurance, premises, training, recruitment costs, computers, software licences, under-utilisation, lab equipment, lab space, insurance, accounting and legal support and so on. If you add up those things for your internal team, you will find the market rate for R&D work. The quotes from potential partners should match this: they should be the market rate after all. When coupled with rapid and reliable progress on solving a valuable problem, the cost-effectiveness should be clear.

If you and your team do see the value in an external collaboration, move to Step 2…

Step 2: Think about what you’re asking for

What is it that you need?  This will inform what you’re looking for in an external partner.

When it comes to specifying the size and shape of a project, there are 3 competing factors:

  • Quality.
  • Time.
  • Cost.

Typically, you can optimise a project for any 2 of the above.

Step 3: Find out from peers who is good

Reputation is everything. A really good innovation partner will have a good reputation which others in your field will know about.  If you don’t know who to ask, maybe former colleagues at another company can help [Springboard has gained many clients this way].  You can always get in touch and ask us!

You may already know that a company’s name being well-known correlates strongly with its marketing budget, and not necessarily with the quality of its work.

It is about the people, not the brands.  We have found that the most important ingredient in successful development projects is the quality of the people.  Two qualities stand out as being vital:

  • Their technical and project management ability; and (no less)
  • Their ability to communicate and work with you (and you trust them).

Really good engineers and scientists will be able to use the right technique and equipment even if they have not used exactly the same things before.  On the other hand, it could be folly to expect mediocre engineers and scientists to develop market-leading high performance, usable and safe products, or fix non-trivial technical problems.  Perhaps ask yourself this provocative question: “How many opportunities do I have to get this project right?”

There is sometimes a downside to really capable people: they can be arrogant and therefore not so good to work with.  The best way to assess this is Step 4…

Step 4: Talk with the potential partners

It is worth spending the time to speak with potential partners because a website or word-of-mouth cannot give the full picture about the quality and attitude of the people actually working at the potential partner company.  By definition, case studies on websites will be very old because they have to be outside of confidentiality terms.  Therefore, the people that developed those devices might not be working at that company anyway.

Talking with the company can help you assess:

  1. Would I want to work with these people?  Are they listening to me?
  2. Are they capable people who I trust to deliver the project successfully?
  3. Do they understand the constraints of the project?

Here is a list of common pitfalls to watch for:

  1. Be aware of the A-team/B-team.  You might be talking to some experienced, capable people during the negotiation and planning, only to find that you get a completely different set of people working on the project once it starts.  You can minimise this risk by seeking assurances about who would be working on the project: the partner should be able to at least be sure of the project leader.
  2. Ensure the correct incentives.  If the potential partner has internal projects, it will be wanting to secure its own IP.  If it has experience in your field, it is probably going to want to secure its own IP in your field.  Development contracts can say that IP will belong to you, but perhaps you do not want an incentive for people working on your project to keep the best ideas for their company.  The best way around this is to use a partner which does not have internal projects at all.
  3. Location is almost irrelevant.  If you work for a leading multinational organisation, you probably want to find the best team in the world to deliver your projects – why not?  The probability of having an excellent team available down the road is slim.  If you do, that’s great!  If you do not, it does not tend to matter these days whether they are 500 miles away or 1,500.  Weekly web conferences cover most project updates, and regular face-to-face meetings are easy in this age of cheap and convenient air travel.
  4. Size is important, but maybe not how you think.  A partner who is too small (one or two people) might not have the breadth and depth of the skills that you need, and you would be at the mercy of any one person being sick or taking holiday when you need them most.  A large partner will prioritise their largest projects. If your project is many millions of dollars in each phase, great! if not, you might find you are not at the front of the queue for resources if you use large partners.
  5. Will the rest of your company treat your partner well?  You may have found the right partner who you trust and you’re really keen go get a great project going. It helps the relationship, and therefore chances of success, if your procurement department agrees to reasonable payment terms, and your accounts department fulfils its obligation to pay on time.

Step 5: Decide who you want to work with

This may be the hardest step.  There are any number of approaches to come to a decision…

Factors such as trust in the people, and your belief in their ability to deliver are hugely important.  Therefore, a spreadsheet of metrics (beloved by procurement departments) is probably not the best way to decide between potential partners.

Perhaps the best way is to think about which partner you would prefer to have a long-term business relationship with, and see if their match to the current project need is good enough.

 

We hope that you have found this post helpful!

If this post has teased any thoughts or questions, please either write a comment below, or get in touch.  We would love to hear from you.

 

Strategies for faster R&D: Break it into manageable steps

When Edmund Hillary and Tenzing Norgay climbed Everest for the first time in 1953, they didn’t just take a giant leap for the top. Rather, they conquered the 8000 meter giant in a series of 10 centimetre steps with manageable milestones along the way.

Everest

An R&D analogy is a company who had spent years developing a new biopsy product in which a rotating blade advanced over a needle used as an anchor. The samples were small and unreliable, so customers were losing confidence. They had tried a bigger motor, sharper blade, different shape, but to no avail. Generation 4 was on the market but still too few customers.

Instead of leaping immediately for a whole new design, we broke the challenge down into a series of steps. How strong is the anchor force? How big is the cutting force? Which is larger? These could be measured simply on a standard piece of laboratory apparatus called a tensometer. When the graph was plotted, we could see that the cutting force was far greater than the anchor force, so the device was just recoiling every time it fired.

So the next steps were: how can I make the cutting force smaller? How can I make the anchor force larger?

Breaking down the problem into steps like this means you then spend your time solving the right problem. It might feel that pausing to do a sequence of scientific experiments adds time compared to aiming straight for the whole answer, but in reality it is often possible to find a much quicker route to success. If every step is in the right direction, you’ll arrive at the answer. But if you spend time solving the wrong problem, no matter how elegantly, you get nowhere.

This is an approach we’ve done for our clients many times over, and the savings can often be measured in years.

Please contact Keith Turner if you think we could help you or if you would like to be alerted to the next strategy.

Strategies for faster R&D: Save tooling for later

There’s a great quote by Thomas Edison when asked if he felt like a failure because of all his failed attempts to invent the electric light bulb. “Young man, why would I feel like a failure? And why would I ever give up? I now know definitively over 9,000 ways that an electric light bulb will not work. Success is almost in my grasp.”

Lightbulb

And not one of those 9,000 prototypes was made on a production line.

A situation that our clients commonly find themselves in goes a bit like this. “Yes, I know it’s not quite working yet but time is running out before the product launch next April and so we have to commission the tooling now. Management aren’t willing to let the launch date slip.”

It brings to mind a medical project in which the disposable part had been pushed through to injection moulding. The trouble was that revisions to the design were still being made. It was possible to modify the tool, but each time that happened, it took six weeks to get the next parts released before they could be tested.

Earlier in the same project, we had been prototyping the disposable component on our CNC mill. You could do a test, modify the CAD, set the mill running overnight and test the next iteration the next day.

Short development cycles demand flexibility, and for this it helps to delay tooling until you know the design works in all respects except for those specifically dependent on tooled properties. Even if you need 100 parts for a clinical evaluation, perhaps they can be machined? It might cost $10,000 and some planning ahead in validation, but that’s child’s play compared with a 12 month delay to a multi-million dollar programme.

There’s a whole suite of prototyping methods available today, such as additive methods (SLA, 3D printing, SLS, vacuum casting…) and subtractive methods (machining, laser cutting, EDM…), not to mention various ways of sealing, bending and so on.

In the next article we look at how to break down a daunting, complex problem into a series of manageable steps.

Please contact Keith Turner if you think we could help you or if you would like to be alerted to the next strategy.

Strategies for faster R&D: Change one variable at a time

 

When the Wright brothers were trying to make their great aeronautical leap forward, they didn’t just throw feathers and motors at the problem to see what happened. Rather they tried to determine which of the three key challenges to mastering flight was most critical: wings, engines or control? Looking at the effect of changing one variable at a time helped them to determine that the critical weakness was in control, meaning that they could innovate in this aspect and set the way to their landmark achievement.

Wright brothers

It brings to mind a project where we were developing a cryosurgery probe to kill breast tumours by freezing. We had a functioning system that worked off a heavy gas cylinder but had recently made the exciting discovery that a simple 1 litre flask could be used to drive the probe directly from liquid nitrogen. This was easier to use, smaller, and cheaper, and so a sure-fire commercial advantage for our client. However, when we scaled our new technology up to full size it didn’t work. It wasn’t just slow, it was completely hopeless, and failed to get even remotely cool to the touch. Yet the only difference was the size.

But was it? The new flask was bigger, that’s true. But actually, the bung that sealed it was also a larger diameter. It was also deeper. And it was a different material. And the dip tube was longer to reach to the bottom of the larger flask.

On reflection, there was quite a lot different about the new system, and we had changed it all at once. This meant we didn’t know which thing we had to change to resolve the problem. There was a deadline approaching, and it was tempting to just jump to the end and try stuff in the hope it would work, but with planning we figured that we had a chance to solve the problem in two weeks by starting with the working miniature system and changing one feature per day until we had created the large system. 10 days, 10 features- surely one of those would be the key?

On day 1, we machined a new bung for the small flask out of the same material as we were using for the scaled-up system. It worked perfectly. On day 2 we scaled it up to the larger diameter- still great. On day 3 we extended the dip tube- still chugging along nicely. On day 4 we machined a deeper bung… nothing. A complete failure to freeze. It was now a simple deduction that the deep mass of rubber was sinking heat into our cryoprobe and preventing it from freezing. We added insulation around the tube as it passed through the bung and made ourselves a perfectly working full-size system. All in less than a week, which means we still had time to write the final report for our client who was visiting the next week.

This technique is widely used in science, and is particularly powerful when you have one prototype that you know works, but can’t figure out why another comes up short. If changing one variable at a time does not reveal the problem, there is probably one or more interactions between the variables. We can use techniques in a field of engineering called Design of Experiments to reveal them, but that is a subject for another day.

In the next article we look at how to speed up the development cycle by saving tooling until later.

Please contact Keith Turner if you think we could help you or if you would like to be alerted to the next strategy.

Strategies for faster R&D: High speed video

When the world’s fastest men competed for the 100m Olympic gold medal in Athens, 2004, four athletes crossed the line in a blur. But the event organisers didn’t just squint and pick a winner. Rather, they used high speed video to slow down the motion and changed the method of observation so that it became clear that the new champion was Justin Gatlin.

Olympics

It brings to mind a project I once worked on where we were trying to control air flows inside a dry powder inhaler. The powder kept ending up in the wrong place, and nobody knew why. We had tried different geometries, but to no avail. Finite element modelling hadn’t helped either.

“You can’t see what’s going on because it’s opaque”, people said. Well, true to a point, but with only a little effort it was easy to prototype transparent parts and set up a video camera at 2000 frames per second to visualise the particles. It was beautiful, and you could see each particle whirling about on its journey from the hopper to its final resting place stuck on the side wall. It soon became apparent that the problem started as the particles crossed a particular join in the moulding. This enabled us to focus our attention on that particular problem spot, and we soon found a leak. It was then a simple engineering job to seal the leak and recover the performance that was expected.

We have used high speed video on numerous projects at frame rates over 100,000 per second. Sophisticated techniques can be used to quantify stresses in moving parts and relate their behaviour to material properties. There are also more sophisticated variations, such as stroboscopes and particle image velocimetry, which uses pulsed lasers to visualise the movement of particles over tens of microseconds.

Have you ever had your prototype working, only to see it do something unexpected in its next iteration? In the next article, we look at a technique for staying at the best performance.

Please contact Keith Turner if you think we could help you or if you would like to be alerted to the next strategy.

Strategies for faster R&D: Critical Observation

Nearly 200 years after its inception, Darwin’s theory of evolution still lives as one of science’s greatest breakthroughs. Yet Darwin made this monumental advance in understanding without the use of any computer, internet, or modelling software. He used direct, critical observation and a sceptical mind.

Darwins finches

It brings to mind an occasion when I was trying to work out why an ink-jet filter was blocking. The blue pigment sludge that built up on the filter over 30 minutes was causing the printhead to fail way short of its 100 day lifetime target. We had tried all the obvious things: bigger holes, shaking the mesh, scraping it clean, measuring the reduction in flow-rate, but all without success.

Because the pigment particles were only 1 micron across, we found it hard to work out what was going on. But is it really that difficult? There was a microscope on the bench next door and one of those swan lights that lets you change the illumination angle. With some new brackets and a special transparent cap, it was possible to set the filter up and running on the microscope and watch the particles. As they approached the mesh, some would stick to the wire material. Then the next would stick to the first particle, and another until long chains were formed that bridged the hole and it blocked. Then I tested a mesh with smaller holes and to my amazement, it actually took longer to block. As the particles approached the small holes, they sped up to get through the restriction, rather like a rapid in a river. All this extra speed caused them to dislodge other stuck particles and prevent blockage.

So the answer was to make the holes smaller, not bigger! And it was understood simply by looking very carefully.

In a modern lab there are all sorts of ways to help you look. Optical microscopes, electron microscopes, laser strobe systems are just a few of them.

In the next article, we look at one particularly useful way to assist critical observation.

Please contact Keith Turner if you think we could help you or if you would like to be alerted to the next strategy.