US-12624907-B2 - Methods, devices, and systems for control of heat transfer using spin crossover

US12624907B2US 12624907 B2US12624907 B2US 12624907B2US-12624907-B2

Abstract

The invention provides methods, devices, and systems for applications requiring control of heat transfer, such as thermal management of electronic device, cooling, heating, and energy storage. The invention provides a method of controlling the flow of heat by providing a device including a spin crossover material having a low spin state and a high spin state, where the low spin state has higher thermal conductivity than the high spin state, and where the spin crossover material undergoes spin crossover between the low and high spin states in response to a stimulus.

Inventors

Jarad A. Mason
Jinyoung SEO
Ryan MCGILLICUDDY
Jason Braun
Rahil UKANI

Assignees

PRESIDENT AND FELLOWS OF HARVARD COLLEGE

Dates

Publication Date: 20260512
Application Date: 20220830

Claims (20)

1 . A method of controlling the flow of heat comprising: a) providing a device comprising a spin crossover material having a low spin state and a high spin state, wherein the low spin state has higher thermal conductivity than the high spin state, and wherein the spin crossover material undergoes spin crossover between the low and high spin states in response to a stimulus; b) providing a temperature difference across the spin crossover material; and c) applying the stimulus to control the flow of heat across the spin crossover material.
2 . The method of claim 1 , wherein the stimulus applied is a pressure change, a temperature change, a magnetic field, an electric field, light, or any combination thereof.
3 . The method of claim 1 , wherein step (c) comprises increasing or decreasing a temperature of the spin crossover material to a temperature at which the spin crossover material undergoes spin crossover.
4 . The method of claim 1 , wherein (b) further comprises maintaining the low spin state by applying a first pressure while providing the temperature difference to allow heat to flow across the spin crossover material and step (c) comprises applying a second pressure which allows the spin crossover material to undergo spin crossover to the high spin state to reduce heat flow across the spin crossover material.
5 . The method of claim 4 , further comprising applying a second stimulus to change the spin crossover material to the low spin state.
6 . A method of storing heat energy, comprising: a) providing a device or system comprising: i) a spin crossover material having a low spin state and a high spin state, wherein the low spin state has higher thermal conductivity than the high spin state, and wherein the spin crossover material undergoes spin crossover between the low spin state and high spin state in response to a first stimulus and between the high spin state and low spin state in response to a second stimulus; and ii) a heat sink in thermal contact with the spin crossover material; b) flowing heat energy from a heat source through the spin crossover material into the heat sink while the spin crossover material is in the low spin state; c) applying the first stimulus to switch the material to the high spin state to store the heat energy.
7 . The method of claim 6 , further comprising: d) applying the second stimulus to switch the spin crossover material to the low spin state thereby releasing the heat energy.
8 . The method of claim 6 , wherein the first stimulus and/or second stimulus is a pressure change, a temperature change, a magnetic field, an electric field, light, or any combination thereof.
9 . The method of claim 6 , wherein the first or second stimulus comprises increasing or decreasing a temperature of the spin crossover material to a temperature at which the spin crossover material undergoes spin crossover.
10 . The method of claim 6 , wherein step (b) further comprises maintaining the low spin state by applying a first pressure and step (c) comprises applying a second pressure which allows the spin crossover material to undergo spin crossover to the high spin state.
11 . A method of heating or cooling, comprising: a) providing heat energy to a caloric material through a spin crossover material having a low spin state and a high spin state, wherein the low spin state has higher thermal conductivity than the high spin state, and wherein the spin crossover material undergoes spin crossover between the low spin state and high spin state in response to a first stimulus and between the high spin state and low spin state in response to a second stimulus, wherein the heat energy is provided while the spin crossover material is in the low spin state; b) applying the first stimulus to switch the spin crossover material to the high spin state; c) inducing the caloric material to release the heat energy; and d) applying a second stimulus to the spin crossover material to change to the low spin state.
12 . The method of claim 11 wherein the first stimulus and/or second stimulus is a pressure change, a temperature change, a magnetic field, an electric field, light, or any combination thereof.
13 . The method of claim 11 , wherein the first or second stimulus is a temperature change.
14 . The method of claim 13 , wherein step (a) further comprises maintaining the low spin state by applying a first pressure while providing a temperature difference to allow heat to flow across the spin crossover material and step (b) further comprises applying a second pressure which allows the spin crossover material to undergo spin crossover to the high spin state.
15 . A device for controlling heat flow comprising a spin crossover material having a low spin state and a high spin state, wherein the low spin state has higher thermal conductivity than the high spin state, and wherein the spin crossover material undergoes spin crossover between the low spin state and high spin state in response to a first stimulus.
16 . The device of claim 15 , wherein the first stimulus is a pressure change, a temperature change, light, or any combination thereof.
17 . The device of claim 16 , wherein the spin crossover induced by the first stimulus can be reversed by a second stimulus.
18 . The device of claim 15 , wherein the spin crossover material comprises a transition metal coordination complex.
19 . The device of claim 18 , wherein the transition metal coordination complex comprises Co(ii), Co(iii) Fe(ii), Fe(iii), Ni(ii), Mn(ii), Mn(iii), Cr(ii), Pd(ii), Pt(ii), Au(i), Ag(i), Cu(ii), or a combination thereof.
20 . The device of claim 15 , wherein the spin crossover material comprises a molecular transition metal complex or a 1-D, 2-D, or 3-D polymeric transition metal complex.

Description

BACKGROUND OF THE INVENTION High-performance thermal devices that enable high-contrast, reversible, and active control of heat transfer, such as thermal switches, regulators, and diodes, can be highly beneficial for a wide range of modern technologies, such as thermal management of electronic devices, thermoelectric energy harvesting, and solid-state caloric cooling. To date, a number of mechanisms have been utilized to realize control of thermal transport in materials. Examples include magnetic field-induced switching of molecular orientation in liquid crystals, electric field-induced manipulation of ferroelastic domains in Pb[ZrxTi1-x]O3 thin films, hydration-dehydration in soft materials, light-induced modulation of chain alignment in azobenzene polymers, and order-disorder phase transitions. However, these systems often exhibit a modest conductivity switching ratio (khigh/klow) or low overall conductivities; in addition, the synthetic manipulations required to establish structure-property relationships, e.g., those critical to rationally designing thermal devices, are difficult. Thus, there is a need for new methods, devices, and systems for thermal switching. SUMMARY OF THE INVENTION The invention provides methods, compositions, and systems for solid state heat flow control (e.g., thermal switches and regulators), e.g., with applications in, e.g., cooling, heating, and energy storage. In one aspect, the invention provides a method of controlling the flow of heat by providing a device including a spin crossover material having a low spin state and a high spin state, where the low spin state has higher thermal conductivity than the high spin state, and where the spin crossover material undergoes spin crossover between the low and high spin states in response to a stimulus. The method further includes providing a temperature difference across the spin crossover material and applying the stimulus to control the flow of heat across the material. In some embodiments, the stimulus applied is a pressure change, a temperature change, light, a magnetic field, an electric field, or any combination thereof. In some embodiments, the method further includes increasing or decreasing a temperature of the spin crossover material to a temperature at which the spin crossover material undergoes spin crossover. In some embodiments, the method further includes maintaining the low spin state by applying a first pressure while providing the temperature difference to allow heat to flow across the spin crossover material and applying a second pressure which allows the spin crossover material to undergo spin crossover to the high spin state to reduce heat flow across the spin crossover material. In some embodiments, the method further includes applying a second stimulus to change the spin crossover material to the low spin state. In some embodiments, the stimulus is temperature, and the spin crossover material allows or resists the flow of heat after a pre-determined temperature has been reached, either by cooling or heating. In another aspect, the invention provides a method of storing heat energy. The method includes providing a device including a spin crossover material having a low spin state and a high spin state, where the low spin state has higher thermal conductivity than the high spin state. The material undergoes spin crossover between the low spin state and the high spin state in response to a first stimulus and from the high spin state to the low spin state in response to a second stimulus. The device further includes a heat sink in thermal contact with the spin crossover material. The method further includes flowing heat energy from a heat source through the spin crossover material into the heat sink while the spin crossover material is in the low spin state, applying the first stimulus to switch the material to the high spin state to store the heat energy. In some embodiments, the method includes applying the second stimulus to switch the spin crossover material to the low spin state thereby releasing the heat energy. In some embodiments, the first stimulus and/or second stimulus is a pressure change, a temperature change, light, or any combination thereof. In some embodiments, the method further includes increasing or decreasing a temperature of the spin crossover material to a temperature at which the spin crossover material undergoes spin crossover. In some embodiments, the method further includes maintaining the low spin state by applying a first pressure to allow heat to flow across the spin crossover material. In some embodiments, the method further includes applying a second pressure which allows the spin crossover material to undergo spin crossover to the high spin state. In another aspect, the invention provides a method of heating or cooling employing a spin crossover material. The method includes providing heat energy to a caloric material through a spin crossover material having a low spin state and a h