Science - USA (2020-03-20)

APPLIED PHYSICS

Electricity from

thermal sources

It is desirable to harvest as

much energy as possible from

processes that produce useful

amounts of heat and convert it

from waste into electrical power.

Thermoelectrics and thermo-

photovoltaics can harness and

convert heat waste but tend to

operate at high temperatures.

Davids et al. designed and

fabricated a complementary

metal-oxide semiconductor

infrared photonic device that

can harvest and recover energy

from low-temperature thermal

sources (see the Perspective by

Raman). Using a new conversion

mechanism, they experimentally

demonstrate large thermal-

to-electrical power generation

in a bipolar grating-coupled

tunneling device, rivaling the

best thermoelectric devices. The

device design could be used for

exposure times on the order of

milliseconds, which limits their

responsiveness. Falanga et al.

instead used event cameras

with reaction times of micro-

seconds. For sense-and-avoid

maneuvers, these bioinspired

neuromorphic cameras are more

responsive than conventional

cameras because they measure

changes of brightness in an

image (events), thus effectively

sensing motion. With the addi-

tion of event-based detection

energy harvesting of waste heat

and the development of compact

thermal batteries. —ISO

Science, this issue p. 1341;

see also p. 1301

CELL BIOLOGY

PI(4)P regulates

mitochondrial fission

Mitochondria are dynamic intra-

cellular organelles, the shape

and number of which are regu-

lated by various cell-signaling

pathways. Mitochondrial divi-

sion is driven by the recruitment

of a constricting guanosine

triphosphatase protein at sites

of contact with the endoplasmic

reticulum, but other factors,

including lysosomes, are also

involved. Nagashima et al. now

document an essential role for

Golgi-derived vesicles bearing a

specific lipid—phosphatidylino-

sitol 4-phosphate, or PI(4)P—in

the final steps of mitochondrial

division. Disruption of PI(4)P

production results in mitochon-

drial morphological defects

indicative of an inability to

complete fission. —SMH

Science, this issue p. 1366

COMPUTER VISION

Dodgeball for drones

Uncrewed aerial vehicles,

or drones, use frame-based

cameras for object perception.

However, these cameras have

1336 20 MARCH 2020 • VOL 367 ISSUE 6484 SCIENCE

Edited by Michael Funk

IN SCIENCE JOURNALS

A drone dodges objects using event-based cameras and onboard processing.

RESEARCH

IMAGES (FROM TOP): ELLA MARU STUDIO AND YOON SEOK KIM/JIA LIU, DEISSEROTH/BAO LABORATORIES, STANFORD UNIVERSITY; DAVIDE SCARAMUZZAUNIVERSITY OF ZURICH

BIOTECHNOLOGY

From genetics to material to behavior

I

ntroducing new genes into an organism can endow new

biochemical functions or change the patterns of exist-

ing functions, but extending these manipulations to

structure at the tissue level is challenging. Combining

genetic engineering and polymer chemistry, Liu et al.

directly leveraged complex cellular architectures of living

organisms to synthesize, fabricate, and assemble bioelec-

tronic materials (see the Perspective by Otto and Schmidt).

An engineered enzyme expressed in genetically targeted

neurons synthesized conductive polymers in tissues of

freely moving animals. These polymers enabled modulation

of membrane properties in specific neuron populations

and manipulation of behavior in living animals. —SYM

Science, this issue p. 1372; see also p. 1303

Artist’s conception of neurons,

some of which are genetically

engineered to produce a membrane-

associated conducting polymer