The World Of Microscopic Machines

virtually every vehicle made within the last 20 years contains an astonishing piece of technology that remains dormant sometimes going unnoticed for years until the unthinkable happens when an airbag deploys the electronics of the airbag system take just 15 milliseconds to decide if the forces on the vehicle are severe enough within 60 milliseconds from the instant of impact the airbag is fully deployed the entire process from initial vehicle contact deployment happens at twice the speed of a blink of an eye and at the heart of an airbag system is the same technology that allows our smartphones to detect motion inkjet printers to print and projectors to throw an image on a screen these technologies all rely on the emerging field of micro electromechanical systems [Music] micro electromechanical systems or MEMS are tiny integrated devices that combine mechanical and electrical components traditional manufacturing techniques such as milling turning and molding become impractical at small scales so MEMS devices are fabricated using the same batch processing techniques used to fabricate integrated circuits these devices can range in size from a few microns to several millimeters what makes MEMS devices so powerful is their ability to sense control and actuate on a microscopic scale yet generate effects at a macroscopic scale MEMS technologies are highly interdisciplinary in nature and require engineering and manufacturing expertise from a diverse range of technical areas such as integrated circuit fabrication technology mechanical electrical chemical and fluid engineering as well as material sciences optics and instrumentation their applications span across several industries all of which are manufactured inexpensively and in high commercial volumes because MEMS devices are a hybrid of mechanical and electronic mechanisms they're generally fabricated using a combination of traditional integrated circuit technologies and more sophisticated methods that manipulate both silicon and other substrates in a matter that exploit their mechanical properties in traditional integrated circuit manufacturing known as photolithography a wafer is first coated with a substrate of silicon and its surface is oxidized the oxide surface is then coated with an ultraviolet sensitive polymer called a photoresist a pattern of ultraviolet light is projected onto the photoresist which is then chemically developed into a mask on the surface during mask development the more common positive photoresist becomes removable by the developing agent when it's shielded from UV light while a negative resist is removable in areas exposed to UV light atoms are radiated onto the exposed regions penetrating into the silicon beneath in a highly controlled manner changing its conductive properties the unmasked oxide layer is chemically etched away and the remaining photoresist chemically washed away and this process is repeated dozens of times using the remaining layers of oxide as a mask for each subsequent layer the build up of layers of material with different semiconductive properties form the circuitry of the chip aside from its electrical properties silicon has excellent mechanical properties as it forms the same type of crystal structure as diamond though much weaker and it is harder than most metals it's also surprisingly resistant to mechanical stress having a higher elastic limit than steel in both tension and compression MEMS fabrication much like integrated circuit fabrication involves the addition or subtraction of two-dimensional layers on a substrate based on photolithography and etching the 3d components of MEMS devices are due to patterning and inter of the 2d layers stacked on each other the manufacturing process for these devices fall into three general classifications bulk micromachining surface micromachining and high aspect ratio micromachining or harm in bulk micromachining the substrate is removed in a manner similar to traditional integrated circuit techniques an oxide mask is created and the exposed substrate is etched away the pattern of itching is determined by the type of etchant isotropic etchant remove material equally in all directions while anisotropic etchant are limited by the geometry of the structure to be etched anisotropic etchant usually etch faster in a preferred direction the etch resistance of the substrate can also be controlled by selectively bombarding it with atoms of boron in intermediate steps using traditional photo lithography techniques while traditional wet chemical etching can be used a more common approach is the use of a reactive gas driven into a plasma state via radiofrequency energy in an etching process known as reactive ion etching surface micromachining by comparison is predominantly additive in nature and is used to create more complex MEMS based machinery material is deposited on the surface of the substrate in layers of thin films these layers can be either structural or an oxide based scaffolding known as a sacrificial layer the scaffolding is then etch towei leaving only the structural layers surface micromachining can create very complex structures with overhangs it can be used to create sliding structures actuators and free moving mechanical gears even microscopic motors have been achieved using enhanced variants of the process in order to form more complex and larger MEMS structures Micro Machines silicon wafers can be bonded to other materials in a process known as fusion bonding it's a technique that allows the seamless integration of multiple layers via atomic bonding between them fusion bonding allows for the use of more exotic materials such as metals glass ceramics and even organics such as polymers enzymes antibodies and DNA my aspect micromachining differs dramatically from the other two techniques in that it's reminiscent of traditional casting typically a metal base is first coated with a thick acrylic layer then through a mask x-rays are projected onto the surface creating a shaped cavity electroplating is then done to fill the cavity with metal and finally the acrylic is etched away leaving an embossed metal structure high-aspect micromachining is one of the most attractive technologies for replicating micro structures and a high performance the cost ratio some common products Micro Machines with this technique include fluidic structures such as nozzle plates for inkjet printing and micro channel plates for disposable microtiter plates that are used in medical diagnostic applications let's take a look at those popular applications of MEMS devices we mentioned earlier and explore how they function the accelerometers used in automotive airbag sensors were one of the first commercial devices using MEMS technology they measure the rapid deceleration of a vehicle upon hitting an object by sensing a change in voltage based on the rate of this voltage change the on-die circuitry subsequently sends a signal to trigger the airbags explosive charge the accelerometer mechanism is composed of a capacitive finger structure consisting of a pendulum assembly that forms the proof mass this compliance structure deflects under acceleration or deceleration this deflection creates a differential capacitance the resulting voltage signal created by this is then processed by the circuitry on the device initially airbag technology used a conventional mechanical ball and tube type device which was relatively complex weighed several pounds and cost several hundreds of dollars the move to MEMS based sensors was directly responsible for the success of MEMS technology and micromachining technology in the industry with over half a building of these devices in vehicle operation today the reliability of the technology has been proven some vehicles even employ dozens of MEMS accelerometers for their traction control braking and handling aids MEMS based accelerometers can even be configured to sense motion in three axes with the rise of smartphones this capability quickly became indispensable in this configuration the proof mass is suspended at the center of a frame by microscopic Springs in a manner similar to a trampoline acceleration in the XY plane is sensed by capacitive fingers fixed to the frame of each respective axis similar to a single axis accelerometer sensor both sensing structures also contain electrodes that can sense vertical travel of the proof mass forming the simultaneous action of a z axis accelerometer accelerometers are not just limited to automotive and mobile phone applications they can also be found in earthquake detection equipment vr gaming systems pacemakers high-performance disk drives and even weapon arming systems in most smartphones a MEMS based gyroscopes complement the accelerometer they're also found in navigation equipment avionics and virtually any modern device that require rotation sensing MEMS gyroscopes work by suspending an accelerometer on a platform that in itself uses a MEMS based solenoid to create a constant oscillating motion this configuration exploits the Coriolis effect in which an angular force applied to a moving mass creates a perpendicular force the perpendicular force is sensed by the suspended accelerometer and then translated to a rotational measurement by the on-die signal processing circuitry another hugely successful application of MEMS technology is the inkjet printer head inkjet printers use a series of nozzles to support drops of ink directly onto a medium depending on the type of inkjet printer two popular MEMS technologies are used to accomplish this thermal and piezoelectric MEMS based thermal inkjet printer head technology was invented by Hubert Packard in 1979 the technique makes use of the thermal expansion of ink vapor in order to eject ink within the printer head there is an array of tiny resistive heaters these resistors are triggered by a processor in short pulses of only a few microseconds inked in contact with the resistor is rapidly heated at a rate of a hundred degrees per microsecond vaporizing the ink to form a bubble this process is called bubble nucleation as the bubble expands a drop is formed and pushed out of the nozzle landing on the paper and solidifying when the bubble collapses a vacuum is created which pulls more ink into the printhead from the reservoir in the cartridge sometimes referred to as a bubble jet process thermal inkjet printer heads demonstrate that not all MEMS devices require moving parts to function in a piezoelectric printer head a more direct kinetic proach is used a piezoelectric crystal is located at the back of a chamber in each nozzle the piezoelectric crystal element receives a very small electric charge causing it to vibrate when it moves inward it forces a tiny amount of ink out of the nozzle as the element moves back out it pulls some more ink into the chamber to replace the ink that was ejected though originally developed by Epson this technique is used by all of the major printing companies advances in MEMS fabrication techniques have enabled more ink ejecting elements to be incorporated into a printer head early printers had only 12 nozzles with a maximum resolution of about 92 dots per inch today modern inkjet printers have up to 600 nozzles which can all fire a droplet simultaneously enabling 1200 dots per inch of printing one of the earliest uses of MEMS devices in the form of large mechanical arrays on a single die has been for display applications invented by Texas Instruments digital micromirror device technology often marketed as digital light processing or DLP can be found in consumer projectors high definition projection televisions and large venue projectors such as digital cinemas where traditional liquid crystal technology cannot compete digital micromirror devices are composed of an array of millions of tiny pixel mirror elements each pixel is made of a multi-layer device consisting of an aluminum mirror mounted on hinges these pixels rests on a CMOS memory cell by changing the value of the memory cell electrostatic forces alter the angle of the mounted mirror typically by plus or minus 10 degrees these mirrors can be repositioned rapidly to reflect light from a powerful lamp or LED either through the lens or onto a heatsink known as a light dump because each pixel is rapidly pulsing its reflected light on and off through the lens the level of brightness is controlled by adjusting the ratio of on to off time color is achieved by mixing red green and blue light through the device the two primary methods used are a single chip or a three chip method in the single chip method a synchronized color wheel is used to project frames of each color in succession producing the illusion of a color image this method generally creates a moving color distortion known as the rainbow effect the three-chip method addresses the issue by splitting up light from the projection source into its component colors via prism each primary color is processed through its own dedicated chip and the three reflected images are recombined at the lens this technique allows for more precise and robust color as well as sharper images digital micromirror devices formed the basis for another emerging application of MEMS technology electro-optics optical communications has been the only practical means to address the network scaling issues created by the tremendous growth in data traffic routing technologies that rely on electronics to function as a switching element great bottlenecks as optical signals are switched back and forth to electrical information these bottlenecks can be eliminated by using fully optical networks that offer far superior throughput capabilities MEMS technology has been proven to be an effective tool in this their small size low-cost low power consumption durability and high switching density form a perfect solution to the problem of control and switching of optical signals devices such as wave guides optical switches cross connects and multiplexers have all been produced with success by using a mechanism similar to micro mirror display devices optical signals can be routed from a source signal to hundreds of possible destinations by the steering of light through an actuated microscopic mirror this concept has brought once expensive optical switching components down to the sub dollar level one of the more promising applications of MEMS technologies has been the emergence of biomedical MEMS devices referred to as bio MEMS devices they tend to focus on the processing of fluids at microscopic scales conceptualized as a lab on a chip these devices can incorporate micro machine fluid pumps chemical sensors flow controllers nozzles and valves into their overall design this class of devices enabled the inexpensive rapid and relatively convenient manipulation and analysis of small volumes of biological fluids one of the first and simplest examples of a bio MEMS device is the micromachined microtiter plate a microtiter plate is a flat plate with multiple wells used as small test tubes for testing and analysis MEMS technology has been applied towards creating microtiter plates with working areas under 6 square centimeters they're formed from plastic with high aspect ratio of micromachined micro channels the tiny sizes of these plates enabled automatic filling by the use of capillary action despite the simplicity of these initial applications the future of bio MEMS devices lie in their potential to deliver pharmaceuticals in a highly targeted manner insulin management hormone therapy chemotherapy and pain management can all be accomplished by the careful release of drugs into the body from tiny chambers embedded in a MEMS device some advanced bio MEMS research allow for sensing of the body's own internal chemistry to regulate the release of drugs several bio MEMS research labs have even demonstrated the capture of a single red blood cell and subsequent injection of a protein into it via a 5 micron channel these techniques open the door to direct cellular manipulation with DNA proteins and pharmaceuticals the possibility with MEMS devices are astounding applications from low loss ultra miniature and highly integrated tracking radio antennas to sensors that can measure heat radiation light acoustics pressure motion and even detect chemicals as MEMS based machinery become more refined we get closer to a new frontier of nanotechnology that will disrupt entire industries challenging our current ideas of the economics of manufacturing you

Channel: New Mind

Views: 1,427,287

Rating: 4.9261026 out of 5

Keywords: microscopic machines, mems mechatronics, microelectromechanical systems, how an accelerometer works, how do airbags work, how do airbags deploy, how does tilt sensor work, mems accelerometer sensor working principle, mems accelerometer fabrication process, mems accelerometer, mems gyroscope how it works, mems gyro, how dlp projector works, how dlp works, how optical switch works, microscopic world, lab-on-a-chip systems, lab-on-a-chip, nanomachines, nanotechnology 2018

Id: iPGpoUN29zk

Length: 16min 37sec (997 seconds)

Published: Sat Jul 20 2019

Reddit Comments

[u/burrito_poots]

Same as above, dope vid thanks for sharing homie

[u/epileftric]

This summarizes a whole year of a classes I had at Uni for a subject.

[u/megagrassblaster8000]

Thanks for sharing. This channel is fascinating and very well done. It's amazing to think about the tolerances of machines, that made a machine that will machine a part. And the tolerance of the machine that built that machine to .... and now were down to 50 atoms apart!

[u/comethefaround]

This was an awesome video thanks for sharing.

[u/Bobandbobsbeard]

Wicked cool

[u/ProudFeminist1]

I really like this channel, quite an indepth overview of different engineering topics