Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Piezoresistive heat engine and refrigerator   Heat engines provide most of our mechanical power and are essential for
transportation on macroscopic scale. However, although significant progress has
been made in the miniaturization of electrostatic engines, it has proven
difficult to reduce the size of liquid or gas driven heat engines below 10^7
um^3. Here we demonstrate that a crystalline silicon structure operates as a
cyclic piezoresistive heat engine when it is driven by a sufficiently high DC
current. A 0.34 um^3 engine beam draws heat from the DC current using the
piezoresistive effect and converts it into mechanical work by expansion and
contraction at different temperatures. This mechanical power drives a silicon
resonator of 1.1x10^3 um^3 into sustained oscillation. Even below the
oscillation threshold the engine beam continues to amplify the resonator's
Brownian motion. When its thermodynamic cycle is inverted, the structure is
shown to reduce these thermal fluctuations, therefore operating as a
refrigerator.

34
The categories of this paper are: chem-ph
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
37
The categories of this paper are: supr-con
15
The categories of this paper are: nucl-ex
7
The categories of this paper are: hep-th
27
The categories of this paper are: comp-gas
26
The categories of this paper are: bayes-an
18
The categories of this paper are: econ
2
The categories of this paper are: math
9
The categories of this paper are: nlin
19
The categories of this paper are: eess
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio