MEMS Technology Summit – Day One – AM (2)

CardioMEMS EndoSure Wireless Pressure Sensor

From the MEMS Technology Summit at Stanford University, here are the highlights from the second morning session on Tuesday October 19, 2010:

Professor Thomas Kenny, Stanford University, Keynote: “MEMS Goes Mainstream, but Where are We Going?”

  • What are we trying to do? Make money – others will cover that topic – and to enable capabilities. But we need to look at how well we have achieved this.
  • Nanotechnology promises are un-fulfilled: There has been lots of hype and promises in the literature for over ten years. But what we are missing is the “technology” side of Nanotechnology. Perhaps Nanotechnology is an oxymoron? If we define technology as the ability to make something exactly the way we want it – repeatedly – we do not have this capability at the nano-scale for many structures. We have some hope of uniformity but not heterogeneity (in terms of number of unique outputs).
  • As a DARPA Program Manager he developed the Tip-Based Nanofabrication (TBN) program with the goal of achieving localized control over nanostructures. They want to develop a tool to reach in and make changes at the nano-scale to provide true nano-scale manufacturing.
  • The IBM Millipede program, which was an inspiration for the TPN program, demonstrated the ability to do nano-scale parallel fabrication using AFM cantilevers. However, IBM lost interest when paramagnetic hard disk drives eclipsed the performance of this high density data storage system. The ever present danger is by the time you have your technology ready others may have passed you by.
  • As you progress down in size, one goes from needing a machine shop to VLSI technology for sub-micron fabrication to manipulation on the molecular level. TBN is addressing this need and is off and running with 10 research teams from both universities and private companies.
  • In PowerPoint this is straight forward, how hard could it be?” Not only is the technology difficult (DARPA only funds fundamental research) but it took several years to develop the program and engage the research teams. Two weeks prior to the conference, he retired from his role at DARPA to return to teaching at Stanford.
  • DARPA funding for MEMS peaked at $78 M in 1999 and is running about $40 M per year now. However, they do not DIRECTLY fund MEMS (they fund research programs focused on applications not technology) since it is used in all areas. Now MEMS is an essential element in almost all programs DARPA is looking at. Hence MEMS has “graduated”.
  • What is a MEMS device? He showed several examples that were easy to call a “MEMS” device and others that the audience questioned if they were really MEMS. It may be easier to define a MEMS device based upon the pedigree of the researcher (association to the “MEMS world”) than the actual research. We need to decide if the term MEMS will include everything or needs to be more focused.
  • Twenty five years ago MEMS needed “protected status” – specific project sponsors, funding, facilities, tools, meeting, journals, companies, etc. – to help it grow. But MEMS doesn’t need it anymore so we should stop using the MEMS acronym. The technology needs to be addressed in each of the separate fields and applications. To spark discussion, he suggested that the IEEE MEMS Conference be discontinued after this year. The papers and research could be presented in the conferences that focus on the end applications (i.e. medical research, sensors, etc.).
  • At SiTime they had argued about using the MEMS label to promote the technology. They determined that it added no value to their end customers so the product was not promoted as MEMS. This kept the focus on the end application itself, not the technology, and contributed to the company’s success.

Professor Mark S. Humayun, M.D., Doheny Eye Institute, USC, “Bioelectronic Implants for Ophthalmology”

Unfortunately Dr. Humayun was unable to present. His research topics are:

  • Electrical stimulation of the retina
  • Retinal prosthesis
  • Retinal disease
  • Instrumentation for vitreoretinal surgery

as listed on his web page.

Professor Mark A. Allen, Georgia Tech University, “Wireless Implantable Medical Microsystems: From Development through Clinical Trial to Commercial Product”

  • In 2001, he co-founded CardioMEMS to commercialize wireless sensing and communication technology for the body. Their primary product is a RF addressable pressure sensor to detect aneurysms.
  • Coronary death has been reduced in half since 1980 while the rate of heart failure has almost tripled. This is due to advances in interventional medicine saving additional lives but typically these additional surviving patients have weakened heart muscles. Therefore the greater need is for long term monitoring similar to diabetics monitor their glucose levels. The data provides the doctor with earlier (compared to infrequent monitoring) indicators allowing a change in medication or other intervention to prevent heart failure or coronary death.
  • No active electronics are implanted. The resonant frequency of the implanted device is read out by an external antenna. The basic technology was published in 1967 in the IEEE Transactions on Biomedical Engineering. However, the fabrication technology at the time did not make this approach practical.
  • The three main issues in long term device implantation are:
    • Stability of the device – in terms of sealing, over growth of tissue, corrosion & fatigue
    • Biocompatability
    • Readout distance – the deeper the device is implanted the greater the power and/or sensitivity of the readout device
  • Their solution is a four part system:
    • MEMS implantable pressure sensor (photo above)
    • Catheter based delivery system
    • Readout electronics
    • Database to track patients
  • From their six month clinical trials they do not see a significant change in the first three months (most likely due to initial adjustment). However, in the following three months there is a 38% (annualized) reduction in heart failure.

Questions:

  • System bandwidth? As the rate of obesity increases, a large range of implantation depth is required. Therefore, their device is very low frequency, with a 20 to 30 MHz resonant frequency, to work with near field.
  • How long to develop? From first idea to commercialize this technology in 1996 to first product cleared by the FDA in 2005 is about 10 years. A second device they are submitting to the FDA this year, if approved, will be about half the time.
  • How much to develop? As to the often quoted $40 M one would need to double the cost due to the need for the clinical trial. Their 550 person trial was very expensive – however much cheaper than a pharmacological trial with thousands of participants. In addition, the laws of physics that govern physical devices are well understood, so the designers are fairly confident of success. With pharmacology, we are not always sure how the drugs will work.
  • What was the hardest FDA requirement as a MEMS person? He was happily surprised as a consumer but was very concerned as a developer about how thoroughly the FDA reviews things. For example both Nitinol wires and Teflon are approved for implantation. However they had to prove that the combination of Teflon coated Nitinol wires were safe. In terms of MEMS, the hardest issue was to design a device with the longevity required combined with minimal drift since it has a service life of ten years and there are no means to recalibrate it.
  • Did they make a decision to not include cell phone technology in their device? They have incorporated cell phone technology in their system in the physician interface to enable patient “management by BlackBerry” which is becoming more common. Going forward they will move the cell phone closer to the device.
  • Since a lot of MEMS products have packaging issues, what else did they look at? An impedance measurement (instead of their pressure measurement) is even less invasive. You still have an implantable sensor but it is not internal to the cardiovascular system. The downside is it is not as precise. So, in the end there may be a spectrum of approaches which need to be managed. Perhaps from smart scales to implantable devices – all helping to manage these chronic conditions.

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