Steel bottom
Polycaprolactone shell Steel bottom
HIGHLIGHTS STOMACH LINING STOMACH LINING
Insulin tip
Spring Insulin tip Spring
copolymer backbone. The synthesis required a sequence of standard atom-transfer polymerisations, and the final block copolymer could be readily purified by dialysis. Adsorption of the block copolymer,
for example, on a silica surface proved to be relatively slow due to a high entropic penalty. However, once adsorbed, the block copolymer stuck to the surface and was remarkably resistant towards changes in pH or high salt concentrations. The bottlebrush polymers were
quite effective in preventing the adsorption of three different test proteins on silica surfaces, as well as E. coli bacteria. A polymer film thickness of just 6nm was consistent with a monolayer of polymer. The authors anticipate that such
polymers with antifouling properties could promise applications for protecting biosensors, medical devices and implants.
Wearable thermal management textiles The human body can absorb or lose heat through infrared radiation at wavelengths around 10micrometres. There are no known textiles that make use of this window to effectively control whether they cool or warm. Yet, many species in nature have developed ways of adapting to outside changes of relative humidity and temperature, keeping an animal warm when exposed to the arctic cold or dissipating heat under a desert sun.
A recent paper has described the
development of a wearable textile capable of adapting to environmental changes by an infrared radiation gating mechanism (X. A. Zhang et al, Science, 2019, 363, 619). The authors used commercially
available bimorph fibres that consisted of strands of hydrophobic cellulose triacetate fused side by side with hydrophilic cellulose (Scheme 3). The knitted fabric was subsequently coated with carbon nanotubes. When hot and wet, the fluffy
yarn collapsed into a tight bundle (Scheme 3). The yarn became open to IR radiation thus allowing the body to lose heat through radiative cooling. Under cold or dry conditions, the fibres were further apart reducing heat losses from the body. The adaptive gating mechanism depended not just on the distance between fibres but also crucially on
Scheme 2 Structure of the bottlebrush polymer that mimics lubricin
Scheme 3 Design principles of an IR gating textile material: under hot/wet conditions the yarn collapses into tight bundles, under cold/ dry conditions the yarn expands with large separation between fibres, at the same time closing the textile towards IR radiation
STOMACH LINING
Hydrophilic Hydrophobic Carbon
nanotubes
Polycaprolactone shell Steel bottom
Insulin tip
Spring
Hydrophilic Hydrophobic Carbon
nanotubes
cold/dry hot/wet
cold/dry hot/wet
IR PTFE balls
- - +
+ + -
- --
- - -
- - -- + + +
- - -
Scheme 4 Buoy- shaped triboelectric nanogenerator containing rolling PTFE balls
Anchored to bottom PTFE balls
- - +
+ + -
- --
- - -
- - -- + + +
- - -
the ability of the carbon nanotubes to vary their IR emissivity. When the yarns collapsed, the IR emissivity of the carbon nanotubes overlapped with the maximum of IR emission from the human body, thus promoting radiative cooling. When the yarns were further apart from each other, IR emissivity moved towards longer wavelength, thus preventing heat loss. Response times were relatively fast (<1 minute). Adaptable clothing could not only be highly useful to ensure survival in demanding environments but also help to reduce energy costs associated with heating and cooling in buildings.
Hydrophilic Hydrophobic Carbon
nanotubes PTFE balls
- - +
+ + -
- --
- - -
- - --
cold/dry hot/wet
+ + + IR Anchored to bottom
- - -
Triboelectric nanogenerators Converting wave energy into electrical energy is a potential alternative energy source. In contrast to tidal power plants, which require a huge financial investment, wave energy converters are much simpler and cheaper to implement. Z. L. Wang and co-workers
Anchored to bottom have looked at the potential of IR
triboelectric nanogenerators for harvesting wave energy (ACS Nano, 2019, 13, 1932). The authors designed a tower-
like tubular buoy, which could be anchored to the bottom of a water tank. Inside the buoy were multiple arc-shaped levels coated with a thin nylon film and two aluminium electrodes per level. Around 20 polytetrafluoroethylene (PTFE) balls, up to 1cm in diameter, were added per level.
Upon movement of the buoy
by a wave, the PTFE balls acquired negative charges on their surface and then induce a positive charge and a voltage spike when they roll over one of the electrodes (Scheme 4). Since the balls on different levels
keep moving in the same phase, power density multiplies with the number of levels and nanogenerators connected in parallel. The authors achieved a power density of 10W/ m3
with a single buoy containing 10
levels, enough to drive 540 light- emitting diodes.
44 06 | 2019
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52
