Liquid crystal elastomers (LCEs) have attracted tremendous interest as actuators for soft robotics due to their mechanical and shape memory properties. However, LCE actuators typically respond to thermal stimulation through active Joule heating and passive cooling, which make them difficult to control. In this work, LCEs are combined with soft, stretchable thermoelectrics to create transducers capable of electrically controlled actuation, active cooling, and thermal‐to‐electrical energy conversion. The thermoelectric layers are composed of semiconductors embedded within a 3D printed elastomer matrix and wired together with eutectic gallium–indium (EGaIn) liquid metal interconnects. This layer is covered on both sides with LCE, which alternately heats and cools to achieve cyclical bending actuation in response to voltage‐controlled Peltier activation. Moreover, the thermoelectric layer can harvest energy from thermal gradients between the two LCE layers through the Seebeck effect, allowing for regenerative energy harvesting. As demonstrations, first, closed‐loop control of the transducer is performed to rapidly track a changing actuator position. Second, a soft robotic walker that is capable of walking toward a heat source and harvesting energy is introduced. Lastly, phototropic‐inspired autonomous deflection of the limbs toward a heat source is shown, demonstrating an additional method to increase energy recuperation efficiency for soft systems.

Flat pasta with designed surface grooves can dynamically morph into three-dimensional shapes when boiled.

As continuous wearable physiological monitoring systems become more ubiquitous in healthcare, there is an increasing need for power sources that can sustainably power wireless sensors and electronics for long durations. Wearable energy harvesting with thermoelectric generators (TEGs), in which body heat is converted to electrical energy, presents a promising way to prolong wireless operation and address battery life concerns. In this work, high performance TEGs are introduced that combine 3D printed elastomers with liquid metal epoxy polymer composites and thermoelectric semiconductors to achieve elastic compliance and mechanical compatibility with the body. The thermoelectric properties are characterized in both energy harvesting (Seebeck) and active heating/cooling (Peltier) modes, and examine the performance of wearable energy harvesting under various conditions such as sitting, walking, and running. When worn on a user's forearm while walking outside, the TEG arrays are able to power circuitry to collect photoplethysmography (PPG) waveform data with a photonic sensor and wirelessly transmit the data to an external PC using an on‐board Bluetooth Low Energy (BLE) radio. This represents a significant step forward on the path to sustainable body‐worn smart electronics.

Despite the impressive performance of recent marine robots, many of their components are non‐biodegradable or even toxic and may negatively impact sensitive ecosystems. To overcome these limitations, biologically‐sourced hydrogels are a candidate material for marine robotics. Recent advances in embedded 3D printing have expanded the design freedom of hydrogel additive manufacturing. However, 3D printing small‐scale hydrogel‐based actuators remains challenging. In this study, Free form reversible embedding of suspended hydrogels (FRESH) printing is applied to fabricate small‐scale biologically‐derived, marine‐sourced hydraulic actuators by printing thin‐wall structures that are water‐tight and pressurizable. Calcium‐alginate hydrogels are used, a sustainable biomaterial sourced from brown seaweed. This process allows actuators to have complex shapes and internal cavities that are difficult to achieve with traditional fabrication techniques. Furthermore, it demonstrates that fabricated components are biodegradable, safely edible, and digestible by marine organisms. Finally, a reversible chelation‐crosslinking mechanism is implemented to dynamically modify alginate actuators' structural stiffness and morphology. This study expands the possible design space for biodegradable marine robots by improving the manufacturability of complex soft devices using biologically‐sourced materials.