Robotic Micro-Scallops Can Swim Through Your Eyeballs

Designing robots on the micro or nano scale (like, small enough to fit inside your body) is all about simplicity. There just isn’t room for complex motors or actuation systems. There’s barely room for any electronics whatsoever, not to mention batteries, which is why robots that can swim inside your bloodstream or zip around your eyeballs are often driven by magnetic fields. However, magnetic fields drag around anything and everything that happens to be magnetic, so in general, they’re best for controlling just one single microrobot robot at a time. Ideally, you’d want robots that can swim all by themselves, and a robotic micro-scallop, announced today in Nature Communications, could be the answer.
When we’re thinking about robotic microswimmers motion, the place to start is with understanding how fluids (specifically, biological fluids) work at very small scales. Blood doesn’t behave like water does, in that blood is what’s called a non-Newtonian fluid. All that this means is that blood behaves differently (it changes viscosity, becoming thicker or thinner) depending on how much force you’re exerting on it. The classic example of a non-Newtonian fluid is oobleck, which you can make yourself by mixing one part water with two parts corn starch. Oobleck acts like a liquid until you exert a bunch of force on it (say, by rapidly trying to push your hand into it), at which point its viscosity increases to the point where it’s nearly solid.
These non-Newtonian fluids represent most of the liquid stuff that you have going on in your body (blood, joint fluid, eyeball goo, etc), which, while it sounds like it would be more complicated to swim through, is actually an opportunity for robots. Here’s why:
At very small scales, robotic actuators tend to be simplistic and reciprocal. That is, they move back and forth, as opposed to around and around, like you’d see with a traditional motor. In water (or another Newtonian fluid), it’s hard to make a simple swimming robot out of reciprocal motions, because the back and forth motion exerts the same amount of force in both directions, and the robot just moves forward a little, and backward a little, over and over. Biological microorganisms generally do not use reciprocal motions to get around in fluids for this exact reason, instead relying on nonreciprocal motions of flagella and cilia.
However, if we’re dealing with a non-Newtonian fluid, this rule (it’s actually a theorem called the Scallop theorem) doesn’t apply anymore, meaning that it should be possible to use reciprocal movements to get around. A team of researchers led by Prof. Peer Fischer at the Max Planck Institute for Intelligent Systems, in Germany, have figured out how, and appropriately enough, it’s a microscopic robot that’s based on the scallop:

As we discussed above, these robots are true swimmers. This particular version is powered by an external magnetic field, but it’s just providing energy input, not dragging the robot around directly as other microbots do. And there are plenty of kinds of micro-scale reciprocal actuators that could be used, like piezoelectrics, bimetal strips, shape memory alloys,  or heat or light-actuated polymers. There’s lots of design optimizations that can be made as well, like making the micro-scallop more streamlined or “optimizing its surface morphology,” whatever that means.
The researchers say that the micro-scallop is more of a “general scheme” for micro-robots rather than a specific micro-robot that’s intended to do anything in particular. It’ll be interesting to see how this design evolves, hopefully to something that you can inject into yourself to fix everything that could ever be wrong with you. Ever.

Source:  here

Rooftop Solar’s Threat to Utilities by the Numbers

The rise of rooftop solar has resulted in a catchy phrase—the “utility death spiral”. It's the idea that utilities will be put out of business by distributed energy. A Lawrence Berkeley National Laboratory study confirms utilities in the United States do have reason to worry but finds that changes to regulations could make solar and utilities friends, rather than foes.

Right now, it's hard to imagine why utility executives worry at all about distributed solar. Even with a rapid spread over the past five years, distributed photovoltaic generation is only about 0.2 percent of U.S. electricity supply and is only one or two percent in states with solar-friendly policies.

Yet the rise of distributed solar has kicked off fierce debates and utility-backed efforts to dismantle net energy metering, which allows consumers to gain credit for excess solar power they generate. One often-quoted utility industry white paper called distributed energy “disruptive” to the industry’s business models.

Intuitively, that makes sense: if consumers offset their electricity bills with rooftop solar, they pay less to utilities, particularly during peak hours when power can be more expensive. Taken to its extreme, it's conceivable for people to rely on solar energy and, perhaps with the aid of batteries or natural gas generators, to cut their ties from electric utilities altogether.

Yet even a modest penetration of distributed solar bites into the earnings of utilities, the Berkeley Lab study found. If distributed solar photovoltaic adoption rose to the equivalent of 2.5 percent of utilities’ retail sales, it would cut shareholder earnings by 4 percent. Meanwhile, the impact on electricity rates for consumers was minimal—only 0.1 or 0.2 percent increase. As solar penetration goes higher, the economic impact rises along with it. In a scenario in which 10 percent of generation came from rooftop solar, the reduction in shareholder earnings ranged from five to more than 40 percent.

How much solar affects earnings depends on the type of utility, according to the Berkeley Lab study. In its analysis, it created two models for utilities. One is a vertically integrated utility in the Southwest United States that owns power generation and the physical network. The other is a "wires-only" utility in a deregulated market in the Northeast United States.

Solar reduces the amount of money utilities need to pay for fuel to generate power, but those savings are offset by “revenue erosion” from lower sales and from deferring investment in poles, wires, and other infrastructure. Wires-only utilities, many of which are in solar-friendly states in the Northeast, are more financially vulnerable because they have fewer opportunities to invest in power generation and transmission to earn revenue, the study's author's said.

The Berkeley Labs authors concluded that incremental changes to the regulations that govern utilities could address the economic dislocation caused by distributed energy. For example, utilities could charge higher fixed monthly fees and rely less on kilowatt-hour sales. Utilities could also own distributed PV systems or have customer solar count toward state renewable portfolio standards, which mandate that a portion of their energy come from renewables.

“One important contribution of this work is to highlight the degree to which the impacts of distributed PV on utility shareholders and ratepayers can depend on particular details of the utility’s operating and regulatory environment,” co-author Andrew Satchwell said in a statement.

The Berkeley Lab study is important because it tries to find solutions to how utilities can earn money in a world with more distributed solar. Some people may want to completely disconnect from the grid but it’s worth noting that utilities provide a good deal of benefit to solar owners. Grid-connected solar PV systems effectively use the grid as a big battery, absorbing excess power without having to purchase actual batteries or back-up generation. At the same time, it seems fair to recognize the value of solar to the grid as a whole, such as reducing peak demand and lower fuel costs.

It's unlikely that this debate will cool off anytime soon. Another Berkeley Labsstudy published this month found the price of residential solar continues to drop and, as installation costs come down, solar is poised to continue growing in the years ahead.

source: here