Over the past decade, smartphones have evolved far beyond their original purpose, integrating everything from complex applications to higher-quality cameras. Yet with each new capability comes the demand for more power – and with it, the need for more regular recharging. Given the need to be connected to a power socket for charging, it’s usually an act that takes the “mobile” out of mobile phone.
Several innovations are exploring solutions to this issue of ‘battery drain’. The development of more energy-efficient chips will provide the processing needed for the next generation of app and smartphone capabilities while consuming less energy. Alongside this, advances in energy management chips will more efficiently convert and distribute power within the device. And research into new energy harvesting materials and techniques may, ultimately, see smartphones able to charge themselves.
Advancements in smartphone chip efficiency and power management
The semiconductor sector continually looks to deliver increased performance while reducing power consumption. Smartphones make use of the most advanced semiconductor process technologies. Today, this typically means sub-5nm node processes, though even smaller process nodes are in development. In simple terms, smaller nodes mean smaller transistors, which allows greater transistor density in the same area of silicon. This is key to increased performance but also supports improved energy efficiency.
Several factors support the enhanced energy efficiency and reduced power consumption of the latest generation of smartphone chips. These include shorter interconnects between transistors, lower operating voltages required by smaller transistors, transistor architectures that reduce power leakage (an issue that can increase as process node size decreases), and chips which dynamically adjust power based on device workload.
Further to the overall advancement of semiconductor process technologies, there has been an emergence of chips specifically designed for power management in devices. Power Management Integrated Circuits (PMICs) – including those from ST – control, allocate, and regulate power delivery within devices and are fundamental in optimizing performance and extending battery life. As an endorsement of the importance of power management to the smartphone sector, the PMIC for smartphones market, already valued globally at over $6 billion in 2022, is expected to grow to over $10 billion by 2030.
The PMIC within a smartphone converts power from the battery to the specific voltages needed by components like the CPU, GPU, modem, display, and memory, ensuring that each component receives stable power, crucial for performance and reliability. The PMIC also controls how power is routed to different subsystems based on usage, potentially cutting off power to unused modules – for instance GPS or Bluetooth – to save energy. The PMIC also manages battery charging itself, protecting the battery from overcharging, overheating, and over-discharging, enhancing battery life.
While improving the energy efficiency of chips and overall power management within devices will help extend battery life, research and development continues in relation to materials that may ultimately remove the need to physically recharge mobile devices entirely.
The emergence of energy harvesting materials
Piezoelectric materials, which occur both naturally or can be artificially manufactured, generate an electric charge when subject to pressure. Piezoelectric materials themselves aren’t a new discovery. Indeed, anyone who’s owned a quartz wristwatch has benefitted from their natural capabilities. But their potential in smartphones is just being unlocked.
The pressure applied to a piezoelectric material’s crystal lattice – the structure of atoms in a solid material – causes the atoms to shift slightly, creating an electric charge. This transformation of mechanical force into electricity is known as the piezoelectric effect. Natural piezoelectric materials include, as mentioned, quartz (or silicon dioxide) but also Rochelle salt, topaz and, in biological systems, bone. Many synthetic piezoelectric materials can also be manufactured.
There are several ways that the electric charge created by physical interaction with piezoelectric materials can be used by smartphones to self-charge. Users simply touching or swiping a screen, pressing device buttons, or even the movement of the smartphone itself in a bag or pocket, can result in an ongoing series of electric charges to extend battery life and reduce the regularity of charging required.
Light, heat, movement, and even air: the broader potential for energy harvesting
In addition to piezoelectric materials, research continues into how almost every natural resource could be used as an energy source for smartphones. Innovations in ultrathin, transparent photovoltaic (PV) cells integrated into smartphone screens or back panels show promising potential in the near-term. Thin film PV cells are relatively low cost, have a high level of technology readiness, and can be integrated easily within the case of a smartphone. Additional advantages are that PV cells add negligible weight to a smartphone and have the best energy per volume generation, particularly outdoors. Working in ambient light, PV cells could provide continuous “trickle charging” to mobile devices.
Similar in some ways to piezoelectric materials, triboelectric energy harvesting uses friction between materials – for instance when swiping a screen – to generate electricity. Rather than electric charge generation being a property of the material itself, triboelectric energy harvesting works more like static electricity, where electrons move between two materials when they are rubbed or moved apart.
Thermoelectric energy harvesting converts changes in temperature to electricity. Flexible thermoelectric materials might therefore be able to turn an individual’s body heat into electricity and therefore provide passive energy harvesting for a smartphone or mobile device. Again, some “self-winding” wristwatch wearers will be aware of motion-based battery charging, where simply moving while wearing the watch extends the battery life considerably. Similar kinetic energy harvesting could also be used in smartphones, where tiny mechanical generators convert motion – an individual walking or running, or a device being shaken or tilted – into electricity.
Future micro-electromechanical system (MEMS) may even focus on converting air to energy through air powered micro fuel cells. The process uses oxygen in ambient air in an electromechanical reaction creating electricity. Such fuel cells could, ultimately, become a replacement for lithium-ion batteries in smartphones.
Providing power for our primary computing devices
For many, the smartphone has become the primary computing device used to manage their personal and professional lives. The processing power of current and next generation smartphones is moving towards equality with that of laptop computers.
With the need to remain as portable as possible, however, this means that the additional performance must be matched with improved energy efficiency and a significant improvement in battery life. Ultimately, smartphones will use a combination of many of the techniques described above to optimize device performance while harvesting energy to extend battery life, reducing the reliance on regular charging and contributing to a more sustainable ecosystem. The silver screen vision of smartphones and mobile devices that never need charging may still be a way off, but the ability to access peak performance without an anxious search for a power source is within reach.
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