technology is something that, if it didn’t already exist, could be viewed as science fiction. Tiny mechanical structures, controlled through electronics and manufactured using lithography and etching sounds like something dreamt up by a talented novelist. In truth, the technology developed for the manufacture of leading-edge integrated circuits is also ideally suited to creating tiny 3-dimensional, moving structures.
And it is that one word that really sets MEMS apart from ‘run of the mill’ integrated circuits; ‘moving’. Structures built at the nano-scale that can not only move but be accurately controlled opens up a range of applications; perhaps the most familiar is sensing technology — MEMS devices are at the heart of the gyroscopes that now allow smart devices to ‘know’ where they are and which way up they’re pointing, providing a greater level of interaction and a more ‘immersive’ user experience.
But sensors are relatively simple devices, where the movement of a flexible membrane caused by an external influence (typically movement in the case of inertial sensing) is detected using electro-magnetic techniques. Today there is another sector where MEMS technology is arguably even more ideally suited; micro-fluidics for biomedical applications; often referred to as ‘lab on a chip’.
The size of a human cell is around 25um which, in terms of today’s integrated features, is positively enormous. And as a result of the developments made in MEMS technology, in no small way thanks to the sensors mentioned earlier, tiny devices that are capable of manipulating cells for medical analysis can now be developed in an ever-increasingly affordable process.
It’s given rise to a swath of foundries who specialise in MEMS technology. One such company is IMT (Innovative Micro Technology) which states it is the largest pure-play MEMS foundry in the United States, having shipped in excess of 62million MEMS switches — more than all other manufacturers combined, it believes.
The company also lays claim to manufacturing the world’s most sensitive and most complex MEMS devices offering: up to five wafer-stacked products; on-board reflective and refractive optics; 3D microfuidics, and magnetically-driven actuators, using a range of materials including metals, polymers, glass and silicon.
Citing iSuppli figures, IMT expects the market for MEMS devices to see a compound annual growth rate of 11% between 2010 and 2015, reaching nearly $12billion by the end of that period, and while the majority of that is in ‘established’ market sectors (automotive, industrial, CE-mobile) the size of the Medical Electronics sector appears to see steady growth and account for around $500M of the total market by 2015. The applications accounting for this sector will fall largely in to either Biomedical (implantable drug delivery, cell purification, glucose sensors) and Biotechnology (high resolution particle characterisation, gene sequencing, drug discovery, molecular diagnostics and gas chromatography).
Craig Trautman, VP of Business Development, explained that the company is building a repository of IP; with 66 active patent applications it already has 42 issued and a further 49 pending. The majority of patents relate to RF switches and devices, but a significant number are in Life Sciences, Biotechnology and Cell Sorting.
While the development of MEMS devices is historically complex, Trautman stated that it is ‘getting better’; thanks to the company’s growing library of IP and manufacturing patents it is now seeing the time from concept to component coming down. Trautman also feels that the industry as a whole is ‘on the cusp’ of MEMS/CMOS integration: “We can stack CMOS with MEMS today, but monolithic manufacturing is still evolving. Most devices are wire-bonded, but real 3D stacking is coming soon.” This development will largely be driven by the market for sensors, believes Trautman.
Microfluidics is described by IMT as the ‘cornerstone’ technology for its Life Sciences division. It is used for drug delivery, cell sorting and purification, and cell synthesis and ultra-high resolution particle characterisation. IMT uses components that can be integrated to create precise control and manipulation of fluids, including active and/or passive reed/gate valves, activated mechanically and non-mechanically, and pumps implemented using actuators to move the fluid through the system (these may be electromagnetic, piezoelectric, electrostatic or thermal).
In addition, complex 3D micro-channels can be fabricated using multiple wafers to create 3D manifold structures, as well as micro-nozzles for precise application and distribution of fluids. IMT says that nearly all of its Life Sciences programs use one or more microfluidic components, adding it is common to integrate full microfluidic systems with optics and other technologies, comprising up to five wafers using wafer-level packaging.
A recent example of a major design win for IMT was the world’s first clinical-scale sterile system for sorting cells. It was announced by Owl Biomedical recently and uses IMT’s cell-sorting MEMS technology to implement the Fluorescence-activated cell sorting (FACS) method.
The cell sorter chip employs optics, microfluidics and electromagnetic technologies, based on a ultra-high speed microscopic fluidic valve which is capable of moving 25um in 15us. This speed, IMT says, is the key to the cell-sorter’s efficacy; diverting ‘targeted’ cells to be separated from materials such as blood or bone marrow.
The MEMS device is fully enclosed in a disposable cartridge, allowing human cells to be processed and purified in a low cost, high performance system that could ‘revolutionise’ cellular medicine.