Emerging Nanoclay Composite for Effective Hemostasis

Uncontrolled bleeding following trauma is associated with a high risk of death. Here, an emerging kaolinite nanoclay composite (iron oxide‐kaolinite, α‐Fe₂O₃‐kaolin_KAc) is developed, based on the natural hemostat hematitum used in traditional Chinese medicine to effectively control hemorrhage. α‐Fe₂O₃‐kaolin_KAc stops bleeding in ≈183 ± 16 s and exhibits higher hemostatic activity than the related compounds FeOOH‐kaolin_KAc (298 ± 14 s), γ‐Fe₂O₃‐kaolin_KAc (212 ± 11 s), and Fe₃O₄‐kaolin_KAc (218 ± 15 s). This rapid effect is attributed to efficient absorption of the fluid in blood, activation of blood platelets, and induction of the coagulation cascade by kaolinite and the aggregation of red blood cells induced by α‐Fe₂O₃. α‐Fe₂O₃‐kaolin_KAc shows slight hemolysis (<0.11%) as compared to kaolinite (30%), which accelerates wound healing. The biocompatibility, hemostatic activity, and low cost of α‐Fe₂O₃‐kaolin_KAc make it a safe and effective agent for preventing massive blood loss after traumatic injury.     

Nanoclay Paste as a Thermal Interface Material for Smooth Surfaces

A paste in the form of a polyol ester vehicle (liquid) containing 0.6 vol.% nanoclay is an effective thermal interface material. Nanoclay with a high conformability and hence a small bond line thickness is preferred, namely montmorillonite containing a quarternary ammonium salt organic modifier (dimethyl dehydrogenated tallow) at 125 meq/100 g clay, after exfoliation by using the vehicle. When it is used between smooth (0.009 μm) copper surfaces at a pressure of 0.69 MPa, the thermal contact conductance reaches 40 × 10⁴ W/m² K, in contrast to the corresponding values of 28 × 10⁴ W/m² K, 28 × 10⁴ W/m² K, 25 × 10⁴ W/m² K, and 24 × 10⁴ W/m² K previously reported for carbon black, fumed alumina, fumed zinc oxide, and graphite nanoplatelet pastes. Between rough copper surfaces (12 μm), the conductance provided by the nanoclay paste is slightly below those of the other pastes. The superiority of the nanoclay paste for smooth surfaces is attributed to the␣submicron bond line thickness; the inferiority for rough surfaces is due to the low thermal conductivity. The conductance provided by the nanoclay paste increases from 31 × 10⁴ W/m² K to 40 × 10⁴ W/m² K when the pressure is increased from 0.46 MPa to 0.92 MPa. This pressure dependence is stronger than that of any of the other pastes studied.     

Nanorobots Constructed from Nanoclay: Using Nature to Create Self‐Propelled Autonomous Nanomachines

Self‐propelled, autonomous micro and nanomachines are at the forefront of current nanotechnology. These micro and nanodevices move actively to perform desired tasks, usually using chemical energy from their surrounding environment. Typically, these structures are fabricated via clean room or template‐based electrodeposition methodologies, which yield relatively low numbers of these devices. To utilize these machines in industrial‐scale operations, one would need an inexpensive fabrication route for mass production of nanomachines. The use of naturally occurring nanotubes, Halloysite nanoclay, to fabricate functional nanomotors in great quantities is demonstrated. These nanotubes can be mined in ton quantities and used as base for the fabrication of nanomachines. In addition, it is well known that the surface groups of Halloysite nanoclay bind strongly with heavy metals, which makes it potentially useful in environmental remediation.     

Engineering Nanoclay Edges to Enhance Antimicrobial Property against Gram-Negative Bacteria: Understanding the Membrane Destruction Mechanism by Contact-Kill

The overuse or abuse of antibiotics has led to serious health problems. During the recent decades, among the various methods used in antibacterial applications, some nanoclay minerals are proved antibacterial or inhibitory to the bacterial growth. However, the antibacterial mechanism of contact-kill based on the intrinsic structure of nanoclays is still unclear. Here, the antibacterial ability of pure clay is enhanced by creating more edge surfaces on kaolinite (Kaol) and the antibacterial mechanism is clarified at the atomic level. Based on experiments and density functional theory/molecular dynamics  calculations, the positively charged Al (OH) and Al (OH₂) species on the edge surfaces of Kaol are confirmed to kill the Escherichia coli cells through direct contact by destroying their outer membrane (OM). The strong hydrogen bonding and van der Waals forces between OM and (110)/(1$\overline{1}$0) surfaces of Kaol lead to the folding of OM. Simultaneously, the proton-coupled electron transfer between Lipopolysaccharide (LPS) and (1$\overline{1}$0) edge surface of Kaol causes the dissociation of phosphoryl groups on LPS. Considering the similarities of most nanoclays on their edge surfaces, this finding may shed some light on the development of new nanoclay-based antibacterial materials in the future.     

Switching in m.i.s.m. and m.i.s.i.m. structures

Switching has been observed in metal?thin-insulator?n-p+ structures, where the thin insulator is SiO2, or polycrystalline silicon. In this letter two alternative structures are discussed in which the n-p+ junction is replaced by a Schottky barrier. In the second device proposed two thin-insulator structures back-to-back are shown to exhibit bidirectional switching.     

Noise behaviour of the m.o.s.f.e.t. at v.h.f. and u.h.f.

The optimum noise figures of an m.o.s.f.e.t. at u.h.f. and at pinch-off are calculated using a simplified equivalent circuit. The noise parameters are also determined experimentally. Theory and experiment are shown to be in good agreement. Noise parameters of the m.o.s.f.e.t. for the frequency range 0.1?0.8 GHz are given.     

Power m.o.s.f.e.t. linear h.f. amplifiers

N-channel silicon m.o.s. transistors for h.f. power applications have been fabricated which are optimised for linear amplification. These devices exhibit 2 W output power and 11 dB power gain at 630 MHz in class-A operation. The intercept point for third-order intermodulation distortion is 48dBm, which is considerably more than the same data obtainable with bipolar transistors.     

U.H.F. low-noise GaAs m.e.s.f.e.t. amplifier for colour t.v. broadcasting translator

Low-noise amplifiers for u.h.f. colour t.v. broadcasting translator use have been successfully developed by using 1 ?m gate GaAs m.e.s.f.e.t.s. The obtained performances revealed that a GaAs m.e.s.f.e.t. has low-noise and low intermodulation distortion characteristics, even in the 500?800 MHz frequency range, compared with a Si bipolar transistor.     

Current-kink noise of n-channel enhancement e.s.f.i.-m.o.s. s.o.s. transistors

An experimental study of the low-frequency-noise properties of n-channel epitaxial silicon films on insulator m.o.s. s.o.s. transistors has been performed. The measurements show an excessive noise contribution at drain voltages corresponding to the current-kink effect for temperatures ranging from 4.2 to 300 K.     

GaAs m.a.o.s.f.e.t. memory transistor

A new non-volatile memory device is reported. This device is a GaAs m.o.s.f.e.t. with charge storage in the gate in which is a double oxide structure of aluminium oxide and GaAs native oxide, both oxides are grown anodically. The fabrication of the device is described and the results of initial measurements on the charging and charge retention properties are presented.     

Wide-range monolithic bipolar?j.f.e.t. c.c.o.

A new monolithic current-controlled oscillator (c.c.o.) has been realised in a j.f.e.t.-bipolar technology. Its main advantages are a highly-linear seven decade frequency range and easy temperature compensation for frequency and output voltage.     

V.H.F. and u.h.f. Gunn-effect oscillators

In this letter, the use of the Gunn device as a broadband negative resistance, somewhat analogous to a tunnel diode, is explored. v.h.f. and u.h.f. oscillators are described; the frequency is determined by an external resonant circuit and is very nearly independent of the parameters of the Gunn-effect sample.     

High-efficiency GaAs m.e.s.f.e.t. amplifiers

High-efficiency c.w. amplification with GaAs m.e.s.f.e.t.s under class-B conditions has been demonstrated. Power added efficiencies as high as 68% at 4 GHz and 41% at 8 GHz have been achieved. Two-tone tests were carried out at 4 GHz. The power added efficiencies at the 3rd-order intermodulation levels of ?20, ?25 and ?30 dB were 49, 40 and 35% respectively.     

Low-noise GaAs m.e.s.f.e.t.s

GaAs m.e.s.f.e.t.s with optimum noise figures of 1.6 dB at 6 GHz have been fabricated by projection photolithography. An equation has been developed for the calculation of optimum noise figure which gives good agreement between calculated and measured values.     

New n-channel m.o.s.f.e.t.s

By using plasma c.v.d. and lift-off, an n-channel m.o.s.f.e.t. with effective channel length of 0.4 ?m has been fabricated. Its main fabrication processes and obtained electrical characteristics are described.     

More active RC filters using the d.v.c.c.s./d.v.c.v.s.

Novel configurations using a differential-voltage-controlled current source, differential-voltage-controlled voltage source (d.v.c.c.s./d.v.c.v.s.) as the active building block are described. The configurations assume that the active building block is divided into two independent parts initially.     

New V-groove double-diffused m.o.s. (v.d.m.o.s.)

A new V-groove double-diffused m.o.s. (v.d.m.o s.) is proposed which combines the V-groove technology and the double-diffused m.o.s. (d.m.o.s.) technology. The fabrication processes arc qualitatively described. The gate is located on the vertical V-shaped surface, and the effective channel length is controlled by the vertical-diffusion process of the double-diffusion step. The v.d.m.o.s. is expected to have a faster speed and higher production yield than the ordinary d.m.o.s.     

Subthreshold behaviour of e.s.f.i.-s.o.s. transistors

Theoretical and experimental results are presented which illustrate the influence of various parameters on the subthreshold behaviour of e.s.f.i.-s.o.s. transistors. The numerical analysis accounts for the thin silicon film and the existence of a second interface. A comparison is made with a corresponding bulk transistor, furthermore, between a two- and a one-dimensional analysis of e.s.f.i.-s.o.s. m.o.s.t. The agreement for real cases is found to be excellent.     

Integrated n.m.o.s. operational amplifier for c.c.d. transversal filters

An integrated operational amplifier employing a new high-gain input stage and implemented with n.m.o.s. enhancement devices is reported. The circuit has been designed with reference to the output differential-charge amplifier of a c.c.d. transversal filter. The performance parameters of the amplifier are presented.